7
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Department of Education
Republic of the Philippines
i
Science – Grade 7
Learner’s Material
First Edition, 2013
ISBN: 978-971-9990-58-1
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Consultant: Merle C. Tan, Ph.D.
Authors: Alvie J. Asuncion, Maria Helen D.H. Catalan, Ph.D., Leticia V.
Catris, Ph.D., Marlene B. Ferido, Ph.D., Jacqueline Rose M. Gutierrez,
Michael Anthony B. Mantala, Cerilina M. Maramag, Ivy P. Mejia, Eligio C.
Obille, Jr., Risa L. Reyes, Ph.D.,
Ma. Dulcelina O. Sebastian, Merle C. Tan, Ph.D., and Rodolfo S. Treyes,
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ii
1
Suggested time allotment: 5 to 6 hours
Unit 1
MODULE
1
SOLUTIONS
Overview
In Grade 6, you have learned about different mixtures and their
characteristics. You have done activities where you mixed a solid and a liquid or
combined two different liquids. In the process of mixing, you have observed that
these mixtures either form homogeneous or heterogeneous mixtures. You have seen
that when all parts of the mixture have the same uniform appearance and properties,
it is homogeneous.
You also learned that when different parts of the mixture are visible to the
unaided eye and these parts are obviously different from one another, it is
heterogeneous. A heterogeneous mixture consists of two or more phases. An
example of a heterogeneous mixture is ice cubes (solid phase) placed in a glass of
drinking water (liquid phase).
Solutions are homogeneous mixtures. When you put sugar into water, the
solid becomes part of the liquid and cannot be seen. You can say that the sugar
dissolves in water or the sugar is soluble in water. Solutions may be solids dissolved
in liquids or gases dissolved in liquids. There are also solutions where a gas is
dissolved in another gas, a liquid in another liquid or a solid in another solid.
Gaseous, liquid, and solid solutions are all around you. Many commercial products
are sold as solutions.
In this module, you will identify some important properties of solutions using
different methods. You will also learn how to report the amount of the components in
a given volume of solution. Towards the end of the module, you will investigate the
factors that affect how fast a solid dissolves in water. At the end of Module 1, you will
be able to answer the following key questions.
What common properties do solutions have?
Are solutions always liquid?
2
Activity 1
What solutions do you find in your home?
Objectives:
After performing this activity, you should be able to:
1. describe some observable characteristics or properties of common solutions
found at home or in stores; and
2. present the data gathered in table form to show some properties of common
solutions you observed.
Procedure:
1. With your group mates, write the names of the products or items brought from
home and describe the characteristics of each of these products. You may
make a table similar to the one below.
Products Found at Home or
in Stores
Characteristics
2. As you observe each product, describe the products in terms of color and
appearance, odor, feel, and taste (for food products).
3. Based on what you have learned so far in Grade 6, which of the products you
observed are homogeneous mixtures? What common characteristics do the
homogeneous mixtures in your list have?
4. Which of these products or items are solutions?
A solution is not always a liquid; it can be solid, liquid, or gas. In addition,
solutions may either be found in nature or are manufactured.
3
Naturally Occurring Solutions
Many materials in nature can be used efficiently only when these are in the
form of solutions. For example, plants cannot absorb minerals from the soil unless
these minerals are in solution.
Seawater is a solution having a higher percentage of salt and minerals than
other sources of water like ground water or rivers. Rainwater is a solution containing
dissolved gases like oxygen and carbon dioxide.
Air is a mixture of gases. Water vapor is present in different amounts
depending on the location. Air above big bodies of water contains more water vapor
than air above deserts. Humidity is a measure of the amount of water vapor in air.
Dry air consists of about 78% nitrogen, 21% oxygen, 1% argon, 0.04% carbon
dioxide and traces of argon, helium, neon, krypton, and xenon.
Useful solutions are found not only in nature; many solutions are made for a
specific purpose.
Manufactured and Processed Solutions
Almost every household uses vinegar for cooking and cleaning purposes.
Vinegar usually contains about 5% acetic acid in water. Some samples of vinegar
are clear homogeneous mixtures (solutions). Other kinds of vinegar are colloidal.
A metal alloy is a solid solution made up of two or more metals or non metals.
For example, bronze is an alloy of copper and tin. Brass is an alloy of copper and
zinc.
Other examples of solutions that are processed include wine and liquor, and
tea (but not instant tea).
In the next activity, you will predict what will happen when you mix a sample
solid or liquid in a given volume of water. Investigate to find out if your predictions are
correct. Explain your predictions using the evidence you have gathered from your
investigation.
Activity 2
What are some properties of solutions?
Objectives:
When you finish this activity you should be able to:
1. compare the evidence gathered with the predictions you made; and
4
2. describe some properties of solutions based on observations.
Materials Needed:










6 cups water
6 pieces, spoons
either of the following: cheesecloth (katsa), old, white T-shirt or filter
paper
2 tablespoons each of the following: sugar, salt, mongo seeds, powdered
juice, cooking oil, two different types of vinegar (one which is clear and
another which appears cloudy)
12 clear bottles or cups or small beakers
2 pieces each, measuring spoons (½ tsp and 1tsp)
2 pieces each, measuring cups (½ cup and 1 cup)
3 funnels or improvised funnel made from 500 mL plastic bottle
1 funnel rack
1 flashlight
Procedure:
1.
Predict which among the given samples will dissolve in water. Write your
predictions in column 2 of Table 1.
2.
Put one cup of water in each of the cups.
3.
Add ½ teaspoon of each of the seven samples. Stir the mixture with a teaspoon
to dissolve as much of each sample as possible. Use a different teaspoon for
each of the cups.
Q1. Describe the mixture that resulted after mixing. Write your answer in column 3.
Q2. How many phases do you observe? Write your answer and observations in
column 4.
4.
Filter the mixture with filter paper using a setup similar to Figure 1. You may
use katsa or old, white T-shirt with the improvised funnel from plastic bottle.
Figure 1. A filtration setup. The funnel is
supported on an iron ring and the filtrate is
received in another container.*
*Philippines. Department of Education. (2004).
Chemistry: Science and Technology textbook
for 3rd year. (Revised ed.). Quezon City: Author.
5
Table 1. Data table for Activity 2
(1)
Sample
solid or
liquid
(2)
Will
dissolve in
one cup
water
(yes or no)
(3)
Appearance
(4)
Number of
phases
(5)
Can be
separated
by
filtration
(yes or no)
(6)
Path of light
(can or
cannot
be seen)
(7)
Solution or
not?
Sugar
Salt
Mongo
seeds
Powdered
juice
Cooking oil
Vinegar
(clear type)
Vinegar
(cloudy)
Note: In column 3, you may describe the mixture in other ways such as
homogeneous or heterogeneous. You may also describe the color of the mixture.
Q3. In which mixture were you able to separate the components by filtration? Write
your observations in column 5 of Table 1.
5.
Place the liquid collected from each filtration in a small beaker or clear
transparent glass bottle. Shine light through the liquid using a flashlight placed
on the side of the beaker. The room where you are working should be dark.
Using a black background may help you see the light across the liquid. If the
room is not dark, you can put the setup inside a cabinet in your laboratory.
Q4. In Column 6, write whether the path of light can be seen across the
liquid.
Q5. Which of the samples are solutions? Write your answer in column 7.
Q6. Based on Activity 2, what are some common characteristics of solutions you
observed?
There are other ways of identifying a solution. You will learn these methods in
Grades 8 and 9.
6
In general, a solution has two types of components: the solute and the
solvent. The solute and the solvent dissolve in each other. The component present in
small amount is called the solute. The particles of solute are dissolved in a solution.
Usually, the solvent is the component present in greater amount. In Activity 2, sugar
is the solute and water is the solvent. Solutes and solvents may be solids, liquids, or
gases.
In Activity 3, you will find out how much solute can dissolve in a given amount
of solvent and find out the type of solution based on whether there is excess solute
or not.
At higher grade levels, you will learn more of the detailed processes that
happen when a solute dissolves in a solvent.
Activity 3
What is the evidence that a solution is
saturated?
After performing this activity you will be able to:
1. determine how much solid solute dissolves in a given volume of water; and
2. describe the appearance of a saturated solution.
Materials Needed







6 teaspoons sugar
1 cup of water
1 measuring cup (1cup capacity)
1 measuring spoon (½ tsp capacity)
2 small clear, transparent bottle
2 stirrers
1 thermometer
Procedure:
1.
Put 20 mL (approximately 2 tablespoons) of water in a small clear transparent
bottle. Add ½ teaspoon of sugar and stir.
Q1. What is the appearance of the solutions? Write your observations.
7
2.
To the sugar solution in step #1, add ½ teaspoon sugar, a small portion at a
time and stir the solution to dissolve the sugar. At this point, you have added 1
teaspoon sugar.
3.
Add ½ teaspoon of sugar to the sugar solution in step #2 and stir the solution.
At this point, you have added one and ½ teaspoons of sugar.
4.
Continue adding ½ teaspoon sugar to the same cup until the added sugar no
longer dissolves.
Q2. How many teaspoons of sugar have you added until the sugar no longer
dissolves?
Note: In this step, you will observe that there is already excess sugar which
did not dissolve.
Q3. So, how many teaspoons of sugar dissolved completely in 20 mL of water?
Note: This is now the maximum amount of sugar that will completely dissolve
in 20 mL of water.
In Activity 3, you have observed that there is a maximum amount of solute
that can dissolve in a given amount of solvent at a certain temperature. This is what
is called the solubility of the solute. From your everyday experience, you also
observe that there is a limit to the amount of sugar you can dissolve in a given
amount of water.
A solution that contains the maximum amount of solute dissolved by a given
amount of solvent is called a saturated solution. If you add more solute to the
solvent, it will no longer dissolve. The solution has reached its saturation point. The
presence of an excess solid which can no longer dissolve is evidence that the
solution is saturated.
A solution is unsaturated when it contains less solute than the maximum
amount it can dissolve at a given temperature. In Activity 3, it is difficult to conclude
that the containers with all solids dissolved are unsaturated simply by observing
them. Some of these may already hold the maximum amount of solute, which cannot
be observed by the unaided eye. If they do, then these are classified as saturated
solutions.
A more measurable way to find out the solubility of a solute is to determine
the maximum amount that can be dissolved in 100 g of solvent at a specific
temperature. There are available data from chemistry books that give the solubility of
common solutes at particular temperatures. Figure 2 shows the solubility of table salt
at 25oC.
8
Figure 2. At 25oC, a saturated solution of table salt has only 36.0 g
(3 tablespoons) dissolved in 100 mL of water. Any additional table salt
will no longer dissolve.
Concentration of Solutions
The concentration describes the relative amounts of solute and solvent in a
given volume of solution. When there is a large amount of dissolved solute for a
certain volume of solvent, the solution is concentrated. A dilute solution has a small
amount of dissolved solute in comparison to the amount of solvent.
You will be able to distinguish between concentrated and dilute solutions from
a simple demonstration your teacher will perform. You will describe the
concentrations of solutions qualitatively (by simply observing their appearance) and
quantitatively (by comparing the number of drops per volume of water).
From Part 1 of the demonstration, you were able to describe the solutions as
having quantitative concentrations of 1 drop/50 mL and 10 drops/50 mL.
Qualitatively, you were able to distinguish the bottle with 10 drops/50 mL more
concentrated (darker) than the bottle with 1 drop/50 mL.
Now that you have distinguished dilute from concentrated solutions
qualitatively and quantitatively from your teacher’s demonstration, you can express
concentration in other ways such as:
(1)
(2)
percent by volume, which is the amount of solute in a given volume of
solution expressed as grams solute per 100 milliliter of solution (g/100 mL),
and
percent by mass, which is the amount of solute in a given mass of solvent
expressed as grams solute per 100 grams of solution.
9
Labels of products sold often show the concentrations of solutes expressed
as percent (%) by volume or mass. The alcohol used as a disinfectant is a solution
of 70% ethyl or isopropyl alcohol, meaning 70 mL alcohol. There are also solutions
sold as 40% ethyl or isopropyl alcohol.
Vinegar is often labelled as “5% acidity,” which means that it contains 5
grams of acetic acid in 100 g of vinegar.
Pure gold is referred to as 24 karats. Jewelry that is said to be 18 karats
contains 18 grams of gold for every 24 grams of the material, the remaining 6 grams
consist of the other metal like copper or silver. This material has a concentration of
75% gold, that is, [18/24(100)]. A 14 karat (14K) gold contains 14 grams gold and 10
grams of another metal, making it 58.3% gold.
The following sample problems show you that there is a way to know the
exact ratio of solute to solvent, which specifies the concentration of a solution.
Sample problem 1
How many mL of ethyl alcohol are present in a 50 mL bottle of a 70% alcohol
solution?
Calculation for sample problem 1
Since the given is a 70% alcohol solution, it means that 100 mL of the alcohol
solution contains 70 mL ethyl alcohol. So, the following calculations show that in 50
mL of the alcohol solution, there is 35 mL ethyl alcohol.
50 mL rubbing alcohol x
70 mL ethyl alcohol
= 35 mL ethyl alcohol
100 mL alcohol solution
All portions of a solution have the same concentration. The composition of
one part is also the same as the composition of the other parts. But you can change
the concentration of solutions. This means you can prepare different solutions of
sugar in water of different concentrations (for example, 10%, 20%, or 30%). In the
same way, you can prepare different solutions of salt in water.
Sample problem 2
A one peso coin has a mass of 5.5 grams. How many grams of copper are in
a one peso coin containing 75% copper by mass?
Calculation for sample problem 2
75% by mass means 75 grams of copper in 100 grams of one peso coin.
10
So, a 5.4 grams one peso coin contains,
75 g copper
x 5.4 g coin = 4.0 g copper
100 g coin
Factors Affecting How Fast a Solid Solute Dissolves
In activities 4 to 6, you will investigate factors that affect how fast a solid
solute dissolves in a given volume of water.
The Effect of Stirring
Your teacher demonstrated the effect of stirring in mixing a solid in water.
You observed that stirring makes the solid dissolve faster in the solvent. Were you
able to explain why this is so?
The Effect of Particle Size
In Activity 4, you will investigate how the size of the solid being dissolved
affects how fast it dissolves in water.
Activity 4
Size matters!
1. Write a hypothesis in a testable form. Describe a test you could conduct to find
out which dissolve faster: granules (uncrushed) of table salt or the same amount
of crushed salt.
2. Identify variables (for example, amount of table salt) that you need to control in
order to have a fair test.
3. Identify the dependent and independent variables.
4. List all the materials you need, including the amount and ask these from your
teacher.
5. Be sure to record your observations and tabulate them. Write everything you
observed during the dissolving test.
6. What is your conclusion? Does the size of the salt affect how fast it dissolves in
water?
7. Does your conclusion support or reject your hypothesis?
11
8. Based on what you know about dissolving, try to explain your results.
To help you explain the process of dissolving, imagine that in a solution, the
particles of the solute (table salt) and the solvent (water) are constantly moving.
Water particles collide everywhere along the surface of the particles of table salt,
especially on the corners and edges. This occurs at the surface of the solid solute
when it comes in contact with the solvent. The particles on the corners and edges
then break away from the crystal and become surrounded by the water particles. So
the solute particles are separated by the solvent particles.
Can you now explain why smaller pieces of salt dissolve faster than larger
ones? You may use an illustration or diagram in your explanation.
The Effect of Temperature
Temperature affects how fast a solid solute dissolves in water. Your solutions
in Activity 3 were at room temperature. In Activity 5 you will investigate how fast
coffee dissolves in cold and in hot water. At what temperature will sugar dissolve
faster?
Activity 5
How fast does coffee dissolve in hot water?
In cold water?
1. Discuss with your group mates how to answer the question for investigation,
“How fast does coffee dissolve in hot water? In cold water?” Write your
hypothesis in a testable form. Describe a test you could conduct to find out how
fast coffee dissolves in cold and in hot water.
Note: Do not use 3-in-1 coffee as your sample. Use coffee granules.
2. Identify variables (for example, amount of amount of coffee) that you need to
control in order to have a fair test.
3. Identify the dependent and independent variables.
4. List all the materials you need, including the amount and ask these from your
teacher.
5. Do your investigation using the proper measuring devices. Be sure to record your
observations and tabulate them. Write everything you observed during the
dissolving test. These observations are the evidence from which you can draw
your conclusions.
12
6. What is your conclusion? Does coffee dissolve faster in cold or in hot water?
Use the observations and results you recorded to explain your answer.
7. Does your conclusion support or reject your hypothesis? Explain your results.
The Nature of Solute
In Activity 6, you will find out if: (1) sugar dissolves faster in hot than in cold
water, and (2) salt dissolves faster in hot than in cold water.
Activity 6
Which dissolves faster in hot and in cold water:
Sugar or salt?
1. Discuss with your group mates how you will do your investigation.
2. Write your hypothesis in a testable form. Describe a test you could conduct to
find out answers to the given two questions above.
3. Identify variables (for example, amount of coffee) that you need to control in
order to have a fair test.
4. Identify the dependent and independent variables.
5. List all the materials you need, including the amount and ask these from your
teacher.
6. Do your investigation using the proper measuring devices. Be sure to record your
observations and tabulate them. Write everything you observed during the
dissolving test. These observations are the evidence from which you can draw
your conclusions.
7. What is your conclusion? Does coffee dissolve faster in cold or in hot water?
Use the observations and results you recorded to explain your answer.
8. Does your conclusion support or reject your hypothesis? Explain your results.
The following questions can guide you:
a. Does sugar dissolve faster in hot water than in cold water? Explain your
answer, based on your observations from the investigation.
b. Does salt dissolve faster in hot than in cold water? Explain your answer,
based on your observations from the investigation.
13
c. Which is affected more by increasing the temperature of the water—how fast
salt dissolves or how fast sugar dissolves? Explain your answer.
You learned from Activity 5 that in general, a solute dissolves faster in water
when you increase the temperature. But the effect of temperature is not that simple.
The type or nature of the solute will affect how fast it dissolves in water.
You observed from Activity 6 that increasing the temperature either makes a
solid dissolve faster or slower in water. For some solutes, increasing the temperature
does not have any effect on how fast the solute dissolves.
Now that you have completed the activities in this module, you have learned
the properties of a solution, the ways of reporting its concentration, as well as the
effects of stirring, particle size, temperature, and type of solute on how fast a solid
dissolves in water.
While learning about solutions, you also had the chance to gather information
and gain new knowledge through the process of conducting science investigations.
You also learned the importance of identifying the variables that had to be controlled
in order to make a good plan for measuring and testing the variables you are
concerned about.
What you have started doing in these investigations is what scientists usually
do when they seek answers to a scientific question or problem. In the next modules,
you will be challenged to ask more questions about materials around you. You will try
to explain answers to your hypothesis (your suggested explanation) after you have
done your investigation.
References and Links
Brady, J.E. & Senese, F. (2004). Chemistry: Matter and its changes, 4th edition. River
Street Hoboken, NJ: John Wiley & Sons, Inc.
Bucat, R.B. (Ed.) (1984). Elements of chemistry: Earth, air, fire & water, Volume 2.
Canberra City, A.C.T., Australia.
Elvins, C., Jones, D., Lukins, N., Miskin, J., Ross, B., & Sanders, R. (1990).
Chemistry one: Materials, chemistry in everyday life. Port Melbourne, Australia:
Heinemann Educational Australia.
Hill, J.W. & Kolb, D.K. (1998). Chemistry for changing times, 8 th edition.Upper Saddle
River, NJ: Prentice Hall.
Kurtus, Ron (13 January 2006). Mixtures.
Retrieved Jan 9, 2012 from
http://www.school-for-champions.com/chemistry/mixtures.htm
Philippines. Department of Education. (2004).Chemistry: Science
technology textbook for 3rd year. (Revised ed.). Quezon City: Author.
14
and
Suggested time allotment: 5 to 6 hours
Unit 1
MODULE
2
SUBSTANCES AND
MIXTURES
Many things around you are mixtures. Some are solid like brass and rocks, or
liquid like seawater and fruit juices, or gas like air. Mixtures contain two or more
components. These components may vary in size. The variation in size may tell
whether a mixture is homogeneous or heterogeneous.
In Module 1, you learned about solutions — homogeneous mixtures. They
have a uniform composition. This makes the appearance of the mixture the same all
throughout. Thus, the components of a solution are difficult to distinguish by the
unaided eye.
In this module, you will learn other examples of homogeneous mixtures. You
will use these samples to differentiate them from substances.
How are mixtures different from substances?
How are they similar?
Separating Components of a Mixture
In the earlier grades, you experienced separating the components of a
mixture. You have done this in varied ways. Try to recall some. What are the
separation techniques do you remember? Were you also able to recall distillation
and evaporation?
Different separation techniques make components of a homogeneous
mixture more distinguishable, that is, those “unseen” components when they are in a
solution become “seen”. Just like in the activity below, distillation and evaporation will
help you “see” the two major components of seawater — water and salt.
15
Activity 1
Seawater! See water and salts!
Part A
Objective
In this part, you should be able to collect distilled water and salts from
seawater.
Materials Needed












seawater
Erlenmeyer flask (sample flask)
test tube (receiver)
glass tube bent at right angle,
with rubber/cork attachment
(delivery tube)
water bath
small boiling chips
metal tongs
spoon


alcohol lamp
tripod
safety matches
wire gauze (asbestos
scraped off)
evaporating dish (or
aluminum foil)
hand lens
Delivery tube
Procedure
1.
Prepare a distillation setup as shown
in Figure 1. Place about 60 mL of
seawater in the sample flask. Add 23 small boiling chips.
TAKE
CARE!
Sample
flask
Receiver
Water
bath
Handle properly
the glassware
and flammable
materials.
Figure 1. Simple distillation setup
2.
Apply heat to the sample flask until you have collected about 15 mL of the
distilled water (distillate).
Note: Make sure the source of heat is not removed while the distillation is in
progress.
16
3.
Set the rest of the distillate aside. You will use it in
Activity 2. Label it properly.
4.
While allowing the remaining
seawater to cool, prepare an
evaporation setup as shown in
Figure 2.
5.
Transfer the cooled liquid to the
evaporating dish. Aluminum foil
may be used as an alternative
for evaporating dish. Note that
the aluminum foil was shaped
like a bowl so it can hold the
sample.
6.
Water bath
Top view of
the
improvised
evaporating
dish using
aluminum foil
Figure 2.
Evaporation using a water bath
Apply heat to the seawater until all the liquid has evaporated. Let it cool. Using
a hand lens, examine what is left in the evaporating dish.
Q1. What do you see? Did you notice
the solid that was left after all the
liquid has evaporated?
7.
TAKE
CARE!
The evaporating
dish may still be too
hot to hold. Use
metal tongs.
The solid that is left behind in the evaporating dish is called the residue. Set
aside this residue for part B.
Part B
Objective
In this part, you should be able to compare the residue collected from Part A
with table salt using flame test.
Materials Needed







residue collected from Part A
denatured alcohol
aluminum cooking foil
table salt
spatula or coffee stirrer
match
safety eyewear (e.g., goggles, eyeglasses)
17
Procedure
1. Preparation
of
aluminum
boxes. Cut 5x5 cm aluminum
cooking foil. Fold the edges of
the aluminum foil to form a
box as shown in Figure 3.
Make at least 6 boxes.
2. In one aluminum box, place
a small amount of table salt.
In another aluminum box,
place a small amount of the
residue from Part A. Take
another aluminum box and
leave it empty.
Figure 3. Aluminum Box
TAKE
CARE!
Always wear your safety
eyewear while doing the
activity.
Handle properly the
glassware and flammable
materials.
3. Add approximately 1mL of denatured alcohol to each box. Light the alcohol
and observe the color of the flame produced. Record this color in Table 1.
Compare the intensity of the flame colors.
Table 1. Color of the flame of the different samples.
Sample
Color
No sample
Table salt
Residue from Part A
Q2. How does the color of the flame of the residue compare with that of table
salt? What can you say about the identity of the residue from Part A?
Distinguishing Substances and Mixtures
Seawater is a solution of many different solids, including table salt, in water.
Since the solids are dissolved in water, decantation or filtration will not work in
separating water from the dissolved solids. Other separation techniques are needed.
18
In the activity above, you were able to separate the components of seawater
through distillation and evaporation. One of these is distilled water. It is considered
as a substance. But what makes distilled water a substance?
In the next activity, you will observe how a substance behaves while it is
being boiled or melted. You will also find out that these behaviors will help you
differentiate substances from mixtures. Moreover, some mixtures like substances are
homogeneous. Given two unlabelled samples, one with water (a substance), and the
other a mixture of salt in water; you would not be able to distinguish one from the
other just by looking at them.
Activity 2
Looks may be deceiving
Part A
Objectives
In this activity, you should be able to:
1.
2.
3.
4.
assemble properly the setup for boiling (see Figure 4);
describe the change in temperature of a substance during boiling;
describe the change in temperature of a mixture during boiling; and
differentiate between substances and mixtures based on how
temperature changes during boiling.
Materials Needed











distilled water
seawater
beaker (50-mL), 2 pcs
aluminium foil, 2 pcs
thermometer (with readings up to
110oC)
cork/rubber to fit thermometer
iron stand/clamp
alcohol lamp
safety matches
watch/timer
graphing paper
Procedure
1.
Place about 15 mL of distilled water
into a beaker. Label it properly.
Describe the appearance and odor
of your sample. In your worksheet,
write your descriptions in Table 2.
19
TAKE
CARE!
Handle properly
the glassware
and flammable
materials.
2.
3.
Cover the mouth of the beaker with
aluminum foil. Using the tip of your pen,
poke a hole at the center of the foil. The
hole should be big enough for the
thermometer to pass through.
Thermometer
Prepare the setup as shown in Figure 4.
Notes: Make sure that the thermometer
bulb is just above the surface of the
sample (about 1 mm). Also, make sure that
the heat is evenly distributed at the bottom
of the beaker.
4.
Begin recording the temperature when the
sample starts to boil vigorously. Record
your temperature reading in Table 2 under
the column, Distilled water.
Sample in
beaker
Figure 4. Setup for boiling
5.
Continue boiling and take at least 5 readings at intervals of 30 seconds after
the liquid has started to boil vigorously. Note even the slight changes in
temperature. Record your temperature readings in Table 2 under the column,
Distilled water.
6.
Stop heating when the liquid sample reaches half of its original volume.
7.
Present your data for distilled water in a graph. Place the temperature reading
along the y-axis and the time along the x-axis. Label the graphs appropriately.
Q1. Refer to the graph and your data for distilled water, what do you notice about
its temperature during boiling?
Q2. How would you define a substance based on what you have observed?
8.
Repeat steps 1 to 7 using
seawater. This time, record
your temperature readings
in Table 2 under the
column, Seawater. Note
even the slight changes in
temperature.
TAKE
CARE!
Make sure that the beaker is cool
enough to hold. Use another
beaker for seawater. Rinse the
thermometer and wipe dry before
using it to test other samples.
Q3. Refer to the graph and your data for seawater, what do you notice about its
temperature during boiling?
Q4. How would you define a mixture based on what you have observed?
20
Table 2. Temperature readings of the liquid samples during boiling at 30-sec interval
Distilled Water
Seawater
Appearance/Odor
Temperature (oC)
at start of boiling
30 sec
60 sec
Temperature
(oC)
after
90 sec
120
sec
150
sec
Part B
Objectives
In this activity, you should be able to:
1.
2.
3.
4.
assemble properly the setup for melting (see Figure 6);
describe the appearance of a substance while it is melting;
describe the appearance of a mixture while it is melting; and
differentiate between substances and mixtures based on how they
appear as they melt.
Materials Needed









benzoic acid
benzoic acid-salt mixture
ballpen cap/coffee stirrer
alcohol lamp
tripod
wire gauze
safety matches



21
watch/timer
cover of an ice cream can (about
7-8 cm diameter)
paper
scissors/cutter
marker pen
Procedure
1.
Construction of an improvised melting dish from a cover of an ice cream can.
This may be prepared ahead.
a)
Trace the outline of the cover of an ice cream can on a piece of paper.
Cut the paper following the outline. Adjust the cut-out so it fits well in the
inner part of the ice cream can cover.
See Figure 5a.
b)
Fold the cut-out into 4 equal parts. Place the folded cut-out on top of the
cover (inner part) of the ice cream can. See Figure 5b.
c)
Following the crease of the paper, trace lines using a marker pen into the
cover. Remove the cut-out. See Figure 5c.
d)
In each radius, locate points which are equidistant from the center. Using
the tip of a cutter, etch and mark these points as X 1, X2, X3, and X4. See
Figure 6.
5a
5b
5c
Figure 5. Guide in constructing an improvised melting dish
Your improvised melting dish should look similar as
Figure 6. Samples will be placed at the X marks. This
melting dish may hold as much as 4 samples at one
time.
Figure 6.
Improvised melting dish
2.
Prepare the setup as shown in Figure 7.
22
TAKE
CARE!
Handle
properly
flammable
materials.
Figure 7. Setup for melting
3.
Using the tip of a ballpen cap, place about a scoop of benzoic acid in X1 and
benzoic acid-salt mixture in X4 marks of the improvised melting dish. Do not put
anything in the X2 and X3 marks.
Note: The figure below illustrates how much one scoop of sample is.
Scoop of
sample
Figure 8. Ballpen cap as improvised
spatula with a scoop of sample
4.
Examine each sample. Describe the appearance. In your worksheet, write your
descriptions for the two samples in Table 3.
5.
Make sure that each sample receives
the same amount of heat. Observe
each sample as they melt.
23
TAKE
CARE!
Do not inhale the
fumes/ vapor.
Table 3. Appearance of the solid samples
Benzoic acid
(X1)
Benzoic acid-Salt mixture
(X4)
Appearance
Q1. What did you observe while benzoic acid is melting?
Q2. How would you define a substance based on what you have observed?
Q3. What did you observe while benzoic acid-salt mixture is melting?
Q4. How would you define a mixture based on what you have observed?
The salt that you recovered in Activity 1 is mainly sodium chloride. It melts at
801 C. Imagine how hot that is! It is about 700oC higher than the boiling point of
water. Because of this and limited equipment, it will be difficult to perform this in a
school laboratory. However, given that sodium chloride is a substance, what could
be the expected observation as it melts?
o
In the next activity, you will apply what you have learned from this module in
classifying unknown samples. This time, you have to decide which setup fits best
with the sample you are given. You have to work out a procedure to identify if the
sample is a substance or a mixture. Try to design the procedure first by recalling
what you have done in the previous activities. Let these activities serve as guides
which you can check side by side with your design. Take note of safety measures
and wait for your teacher to give you the “go signal” before proceeding.
Activity 3
My unknown sample: Substance or mixture?
Objective
In this activity, you should be able to design a procedure that will identify
unknown samples as mixtures or substances.
24
Materials Needed

unknown sample
Procedure
1.
Design a procedure to identify if the unknown sample is a mixture or a
substance. Limit the materials that you are going to use with what is already
available.
2.
Perform the activity that you designed after your teacher has checked your
procedure.
Q1. What is your basis in identifying the unknown sample you have?
There are mixtures that are homogeneous which may be mistaken as
substances. Being so, appearance may not be the best basis to differentiate
substances from mixtures. However, there are ways to tell by noting how a sample
behaves during boiling and melting. In the higher grade levels, you will learn why this
is so.
During boiling, the temperature of a substance changes at the
start then it becomes the same; while the temperature of a mixture
is different at different times.
During melting, a substance melts completely/smoothly within a
short time; while a mixture has portions that seem to be not
melting.
In the next module, you will learn more about substances. Collect as many
product labels as you can, you will refer to them as you identify and classify the
substances present in the product.
25
Suggested time allotment: 5 to 6 hours
Unit 1
MODULE
3
ELEMENTS AND
COMPOUNDS
All
substances are
homogeneous. Some mixtures
are
also
homogeneous,
particularly solutions. Being so,
it is difficult to distinguish
mixtures
and
substances
based on appearance.
However, there are
ways to tell if a sample is a
mixture or a substance. The
temperature of a liquid mixture
varies during boiling but for a
liquid substance, it does not. A
solid mixture has portions that
do not melt but a solid
substance melts completely
within a short time.
In this module, you will find out that substances may be further classified into
two: compounds and elements. You will start with the primary characteristic that
distinguishes them.
How are elements different from compounds?
How are they similar?
Compounds
Like mixtures, compounds are also made up of two or more components. In
Module 2, you separated the components of seawater through distillation. One of the
26
products obtained was distilled water. Also, you have identified distilled water as a
substance.
In the activity that you are about to do, you will again “see” for yourself
components, but this time, “what water is made of”. With the passage of electric
current, components of water may be separated from each other.
This process is called electrolysis. You will use an improvised electrolysis
apparatus like the one shown in the figure below. Commonly available materials
were used to construct this improvised apparatus.
sample
container
1
2
3
4
1
2
3
4
5
6
7
8
9
10
11
5
6
7
8
9
10
11
electrolysis
syringe
stainless
screw
Connect red
wire to positive
(+) terminal of
the dry cell.
Connect black
wire to negative
(-) terminal of
the dry cell.
Figure 1. An improvised electrolysis apparatus
Activity 1
Water, “wat-er” you made of?
Objectives
In this activity, you should be able to:
1.
2.
carry out the electrolysis of water; and
identify the components of water.
27
Materials Needed








TAKE
Be careful in
handling the sodium
hydroxide.
improvised electrolysis apparatus
CARE!
5% sodium hydroxide (NaOH)
solution
connecting wires (black and red
insulation)
9V dry cell
test tube
plastic syringes will serve as “collecting syringe”
incense or bamboo stick
safety matches
Procedure
1.
Fill the sample container of the electrolysis apparatus
half-full with 5% sodium hydroxide (NaOH) solution.
2.
Fill each “electrolysis syringe” with 5% sodium
hydroxide (NaOH) solution up to the zero mark. To do
this, insert the tip of the “collecting syringe” through the
hole of the plastic straw and suck out the air. Refer to
Figure 2. Initially, the plunger of the “collecting syringe”
should be in the zero position. The 5% sodium
hydroxide (NaOH) solution will rise and fill the
“electrolysis syringe” as you pull the plunger of the
“collecting syringe”.
3.
Figure 2. Filling up the
“electrolysis syringe”
with the sample
When the solution reaches the zero mark, fold the straw
with the “collecting syringe”. Refer to the figure on the right.
Repeat the procedure for the other syringe.
Note: In case the 10mL syringe is used for sucking out the
air, you may need to repeat the suction of air to fill up the
“electrolysis syringe” with the 5% sodium hydroxide
(NaOH) solution.
4.
Attach the connecting wires to the bottom tips of the
stainless screws. Attach the black wire to the negative (-)
terminal of the dry cell. Attach the red wire to the positive
(+) terminal of the dry cell. The stainless screw that is
attached to the black wire is the negative electrode; while the stainless screw
that is attached to the red wire is the positive electrode.
5.
Once the wires are connected with the dry cell, electrolysis will start.
Electrolyze until 6-8 mL of a gas is obtained at the negative electrode.
28
6.
Draw out the gas at the negative electrode with the
“collecting syringe”. To do this, insert the tip of the
“collecting syringe” into the straw on the side of the
negative electrode. See figure on the right. Remove
the clip and draw out the gas.
Note: The plunger of the “collecting syringe” should be
at the zero mark before drawing up the gas.
While drawing out the gas, you will notice that the
solution will rise up and fill the “electrolysis syringe”
again. Make sure that the “collecting syringe” will only
contain the gas generated. However, take this chance
to refill the “electrolysis syringe” with the solution.
When the level of the solution reaches the zero mark in the “electrolysis
syringe”, slowly lower down the “collecting syringe” and immediately cover its
tip with your finger.
7.
Refer to the figure on the right. Inject the
collected gas into an inverted test tube and
again cover the mouth of the test tube with
your thumb. Immediately test the gas
collected with a lighted match or bamboo
stick/ incense.
Lighted match
Q1. What happened when you placed a lighted
match near the mouth of the test tube?
8.
Continue to electrolyze until 6-8 mL of the gas is obtained at the positive
electrode.
9.
Refer to the figure on the right. Draw out the gas
from the positive electrode and immediately inject
into a test tube held in upright position. Immediately
test the gas collected by thrusting a glowing (no
flame) bamboo stick all the way down towards the
bottom of the test tube.
Note: Extinguish any flame from the burning stick
but leave it glowing before thrusting it inside the test
tube.
Q2. What happened when you thrust a glowing bamboo
stick inside the test tube?
29
Glowing
bamboo stick
water
Collected gas
Electrolysis decomposed water, a compound, into hydrogen and oxygen.
Hydrogen and oxygen are elements. As you have seen from the activity above,
compounds are substances that consist of two elements. As you encounter more
compounds, you will find out that there are compounds that may be composed of
more than two elements.
In the activity above, you noted that oxygen, the gas collected in the positive
electrode, made the lighted stick burn more vigorously. This means oxygen supports
burning. Hydrogen, the gas you collected in the negative electrode, gave a popping
sound when a glowing stick was thrust into it. The sound comes from the rapid
burning of hydrogen in the presence of air.
Note how different the properties are of hydrogen and oxygen from water.
Hydrogen burns and oxygen supports burning while water extinguishes fire.
Hydrogen is a gas at room temperature; so is oxygen. Water, on the other hand, is a
liquid at room temperature. The compound (in this case, water) that is composed of
elements (in this case, hydrogen and oxygen) has properties that are distinctly
different from the elements. In other words, when elements combine to form
compound, a different substance is formed. In the higher grade levels, you will learn
how this combination of elements happens.
Elements
Each element has different set of properties. No two elements have the same
set of properties. Just like the two elements that were generated in Activity 1 —
hydrogen and oxygen. Even though they are both in gaseous state at room
temperature, they behave differently when exposed to a flame or spark of flame.
Hydrogen gives off a “pop” sound when ignited; while oxygen induces a brighter
spark. This difference in behavior implies a difference in property. In effect, hydrogen
and oxygen are different substances, or to be more specific, they are different
elements.
There are quite a number of elements known in the current time. Thanks to
the works of our early scientists, they were able to systematically organize all of
these elements in what we call the periodic table of elements or sometimes simply
referred as periodic table. You will find one at the back page of this module.
Amazingly, they were able to logically arrange the elements in the table enabling one
to have an idea of the properties of several elements by knowing other elements
related to them. This means that there is no need to memorize the periodic table but
it is an advantage to be familiar with it. Thus, in the next activity, you will accustom
yourself with the periodic table.
30
Activity 2
The periodic table: It’s element-ary!
Objectives
In this activity, you should be able to:
1. be familiar with the layout of the periodic table;
2. know some information about the elements that may be found in the
periodic table; and
3. identify the group number an element it belongs to.
Material Needed

periodic table of elements
Procedure
1.
2.
Every element has a name.
In each box of the table, you
will find only one name. One
box corresponds to one
element.
Using the partial figure of the
periodic table on the right, find where
oxygen is.
For the next questions, please refer to the periodic table of the elements found
at the end of Unit 1. Write your answers for each question in Table 1.
a.
Scientists agreed to give symbols for each element. This is very helpful
especially to those elements with long names. Instead of writing the full
names, a one-letter or two-letter symbol may be used. You can find these
symbols in the periodic table too. It is written inside the same box for that
element. For instance, O is the symbol for oxygen.
Q1. What are the symbols for elements with long names such as beryllium,
phosphorus, germanium, and darmstatdtium?
31
Table 1. Name and symbol of some elements and the group number it belongs to.
Name
Symbol
Group Number
Note: Please add rows as necessary
b.
Notice that most of the one-letter symbols are the first letters of these
elements.
Q2. What are the symbols for boron, nitrogen, fluorine and vanadium?
c.
For the two-letter symbols, most of them start with the first letter of the
element. Notice that the second letter in the symbol may be any letter
found in the element’s name. Notice as well that only the first letter is
capitalized for the two-letter symbols.
Q3. What are the symbols for lithium, chlorine, argon, calcium and manganese?
d.
There are symbols that use letters that were taken from the ancient
name of the element. Examples of ancient names are ferrum (iron),
argentum (silver), hydrargyrum (mercury) and plumbum (lead).
Q4. What are the symbols for iron, silver, mercury, and lead?
e.
In the earlier grade levels, you already encountered elements. You
studied rocks and learned that some are composed of silicon and
magnesium. Some even have gold.
Q5. What are the symbols for silicon, magnesium and gold?
f.
When you were recycling materials, you segregated the objects according
to what these are made of. Some of them are made from aluminum,
copper, tin or carbon.
Q6. What are the symbols for these 4 elements?
g.
In nutrition, you were advised to eat enough bananas because it is a good
source of potassium.
Q7. What is the symbol for potassium?
h.
In each box, you will find a number on top of each symbol. This is the
atomic number. In the higher grade levels, you will learn what this number
32
represents. For now, use it as a guide on how the elements are
sequenced.
Q8. What is the element’s name and symbol that comes before titanium? How
about that comes after barium?
i.
Elements that are in the same column have similar properties. For this,
each column is called a family and has a family name. However, at this
point, you will refer first to each family with their corresponding group
number. Notice that the columns are numbered 1 to 18 from left to right.
Q9. In which group does each of the elements listed in Table 1 belongs to?
There are many elements present in the food you eat —whether it is raw like
banana or those processed like banana chips, biscuits, milk, and juice. These are
mostly nutrients which the human body needs in order to function well. Some of
these are calcium, magnesium, zinc, and selenium. Find these elements in the
periodic table. Can you name more? Did you also find them in the periodic table?
In the next activity, you will find out how these elements are present in the
food you eat. From the product labels, information about the contents of the food is
written — named as Nutrition Facts and Ingredients.
The Nutrition Facts is a list of the
different nutrients provided by the food product
with their corresponding percentage share on
the daily recommended dietary allowance.
Refer to the figure on the right. Notice that
some of these nutrients are elements such as
calcium. Is this food a good source of calcium?
On the other hand, Ingredients give you a list of the materials that have been
added to make the food product. These materials are the sources of the nutrients.
These are the ones that are taken in by the body. Refer to the figure below. Find the
ingredient ferrous sulphate (FeSO4). Ferrous is derived from the Latin name of iron.
Refer to the figure on the right. This is the Nutrition Facts which corresponds to the
33
food product having these ingredients. Find the nutrient iron. How much iron does
this food product give as part of the recommended dietary allowance? From this
product label, you can tell that you will be getting as much as 35% of iron that you
need for the day and you will get it as ferrous sulfate — a compound of iron.
Activity 3
The “matter” on labels
Objectives
In this activity, you should be able to:
1.
2.
3.
4.
name elements that are listed in the Nutrition Facts of a food label;
recognize that the elements listed in the Nutrition Facts are not added
as the elements themselves;
infer the food ingredient that could be the source of those listed
elements; and
recognize that most of these food ingredients are examples of
compounds.
Materials Needed

food labels
Procedure
1.
Refer to the labels of different food products below.
Ingredients:
sucrose, creamer (glucose syrup,
hydrogenated palm kernel oil, sodium
caseinate containing milk, sequestrants,
emulsifiers, nature-identical flavors,
sodium chloride, anticaking agents),
maltodextrin, cereal flakes (wheat flour,
rice flour, malt extract, sucrose, corn
grits, acidity regulator), sweet whey
powder, cocoa powder, iodized salt,
thickener, artificial flavour, zinc sulfate,
iron pyrophosphate.
May contain traces of soya.
Cereal drink
34
Chocolate candy
INGREDIENTS: SUGAR, GLUCOSE SYRUP,
MILK NGREDIENTS, MODIFIED PALM OIL,
UNSWEETENED CHOCOLATE, MODIFIED
VEGETABLE OIL, PALM OIL, VEGETABLE
OIL, COCOA BUTTER, SALT CALCIUM
CHLORIDE, CITRIC ACID, SODIUM
BICARBONATE, SOY LECITHIN, NATURAL
AND ARTIFICIAL FLAVORS.
MAY CONTAIN PEANUTS, TREE NUTS OR EGG.
Ingredients: water, hydrolysed soybean
protein, iodized salt, sugar, natural and
artificial colors with tartrazine, acidulant,
monosodium glutamate, 0.1% potassium
sorbate, natural flavor and flavor enhancer.
Soy sauce
35
2.
List down in Table 2 the compounds in the product label and the constituent
elements. There are cases that you will need to look up the constituent
elements because they may not be obvious from the compound name (e.g.,
citric acid, oil).
Table 2. Compounds and their constituent elements written in the food labels
Food Product
Compound
Constituent Element
Cereal Drink
Chocolate candy
Soy sauce
Note: Please add rows as necessary
3.
The elements iron and zinc are listed in the Nutrition Facts for the cereal drink.
Find out from the Ingredients the source of these elements.
4.
Name three elements present in the Ingredients of the cereal drink which are
not listed in the Nutrition Facts.
As you have learned from the activity above, the elements in food are in
combination with other elements and the resulting compounds are referred to as
minerals. Thus, you are not eating the elements themselves.
A product label that lists sodium as a nutrient means that the composition of
one of the ingredients includes sodium. In the case of soy sauce, one possible
ingredient is monosodium glutamate.
It is very rare and most of the time
dangerous if you take in the element itself. In
Activity 1, you have seen that water did not give
off a “pop” sound nor induced a bright spark when
exposed to a spark or flame, unlike its constituent
elements hydrogen and oxygen, respectively. This
means that the properties of compounds are
different from the properties of the elements it is
made up of. There are cases that the properties of
a compound pose less risk than its constituent
elements. An example is sodium and one of its
compounds. Sodium is an element that burns
Photo credits:
http://www.visualphotos.com/image/1x7465368/sodium_reacting_
when it comes in contact with water. Refer to the
with_water_chemical_reaction
photo above. Imagine the danger that you are in
to if you will be eating sodium as an element. However, sodium chloride, which is a
compound made up of the elements sodium and chlorine, does not burn when it
comes in contact with water. In fact, sodium chloride is sometimes used with water
36
as common food ingredient. Perhaps, you are already familiar with this. Does table
salt ring a bell? Sodium chloride is commonly called as table salt. As you know, it is
safe to eat. Do take note though that it should be consumed in the right amount.
Excessive consumption of sodium chloride may lead to kidney failure. This stresses
the importance of reading product labels. This will let you know how much of a
nutrient you get from a food product. Refer to Figure 3. How much calcium do you
need to consume in a day? How about magnesium? Avoid taking them beyond these
recommended amounts. It may lead to sickness, and even death. It is imperative that
you are aware of what makes up the food that you are eating. You may also refer to
Table 3 on the next page for food sources of some minerals when preparing your
meal.
Figure 3. Recommended mineral intake (WHO, 2004)
37
Table 3. Some elements essential to life*
Element
Macrominerals
Source
Deficiency condition
Rickets in children;
diseases of the bones
in adults such as
softening of the bones
and decrease in bone
mass
Zinc (Zn)
Essential to formation
and maintenance of
bones and teeth;
regulates nerve
transmission, muscle
contraction, and blood
clotting
Catalyst in the synthesis
of energy-carrier
molecules; involved in the
synthesis of proteins and
relaxation of muscles
Maintains regular
heartbeat, water balance
and cell integrity; needed
in nerve transmission,
carbohydrate and protein
metabolism
Part of enzymes;
antioxidant
Regulates amount of
body fluid; involved in
nerve transmission
Component of
biomolecules and ions
Part of insulin and some
154 enzymes
Loss of insulin
efficiency with age
Rare
Fluorine (F)
Needed for glucose
utilization
Helps in the formation of
hemoglobin; part of 11
enzymes
Strengthens bone and
tooth structure
Component of
hemoglobin and
myoglobin
Anemia, tiredness, and
apathy
Part of thyroxin, regulates
rate of energy use
Cofactor for a number of
enzymes
Goiter
Calcium (Ca)
Magnesium
(Mg)
Potassium (K)
Selenium (Se)
Sodium (Na)
Sulfur (S)
Milk, cheese,
canned fish with
bones, sesame
seeds, green leafy
vegetables
Function
Nuts, legumes,
cereal grains, dark
green vegetables,
sea food, chocolate
Orange juice,
bananas, dried
fruits, potatoes
Liver, meat, grain,
vegetables
Meat, table salt,
salt- processed
food
Some proteins
Liver, shellfish,
meat, wheat germs,
legumes
Microminerals or Trace elements
Liver; animal and
Chromium (Cr)
plant tissues
Liver, kidney, egg
Copper (Cu)
yolk, whole grains
Iron (Fe)
Iodine (I)
Manganese
(Mn)
Sea food,
fluorinated drinking
water
Liver, meat, green
leafy vegetables,
whole grains,
cocoa beans
Sea food, iodized
salts
Liver, kidney,
wheat germ,
legumes, nuts
*Source: Chemistry S&T Textbook for Third Year, 2009
38
Fluid loss due to too
much alcohol intake;
heart failure due to
spasms
Sudden death during
fasting, poor nerve
function, irregular heart
beat
Keshan disease (heart
disease)
Headache, physical
weakness, thirst, poor
memory, appetite loss
Anemia, stunted growth
Dental decay
Weight loss, occasional
dermatitis
It is also an advantage if you know the different names of the elements and
compounds. Take the case of the food product label below.
Refer to the Nutrition Facts of the cereal
product on the right. It tells that this cereal product
provides the nutrient, sodium.
Now, refer to the Ingredients. Do you find
any ingredient that could be a source of sodium? It
may seem not, at first. However, knowing that the
other name for sodium chloride is salt, you can
now identify one source ingredient for the sodium
that is listed in the Nutrition Facts.
Note that there are instances that the
Nutrition Facts is incomplete. You may find an
element unlisted but once you check the
Ingredients, you can tell that the food product
could be a source of that element. Refer to the
label of the cereal drink you used in Activity 3. Is
sodium listed in the Nutrition Facts? Is there an
ingredient that could be a source of sodium? When you read product labels, make
sure you do not miss out on these information. This will help you decide if the
product is worth buying.
Any ingredient added to food should be safe to eat in terms of quality and
quantity. By quality, these ingredients must be food grade. A substance undergoes
a process before it becomes food grade. It is only after that, a substance may be
safely added as a food ingredient. If it is a non-food grade substance then it should
not be added to products that are meant to be ingested.
Refer to the product labels for a soy
sauce and a lotion. Notice that potassium
sorbate is a common ingredient. It has the
same function for both products, that is, it acts
as a preservative so the product would last
longer. However, it is important to note that
food grade potassium sorbate was added in
soy sauce; while a non-food grade potassium
sorbate may be added in the lotion.
Notice that the product label does not
indicate if the ingredient is food grade or not.
However, there are government agencies that
make sure the food products that are sold in
the market uses only food grade ingredients.
39
In the next activity, you will encounter another substance that is common to
materials that are not meant to be ingested. However, this substance was made food
grade before it was added as a food ingredient. This substance is iron. This food
grade iron is sprayed onto the food or added as a powder to the mixture. Because it
is the elemental iron that was added as a mixture, its properties are retained. One of
these is its magnetic property. Thus, you can recover the iron present in the food
product by using a magnet.
Activity 4
The iron-y of food fortification
Objective: In this activity, you should be able to recover iron from a food product.
Materials Needed







processed food product rich in reduced iron
magnetic stirrer (magnet with white coating)
blender
water
beaker
measuring cup
forceps
Procedure
1.
Place one cup of the food sample in a blender. Add one cup of water.
2.
Transfer the crushed sample to a beaker. If the mixture is too thick, add more
water.
3.
Make sure that the magnetic stirring
bar is clean. Place it in the beaker
containing the mixture.
4.
Stir the mixture for about 15 minutes
in a magnetic stirrer.
TAKE
CARE!
Do not eat the food
samples and the iron
that will be extracted in
the activity.
Note: If the magnet does not seem to move, the mixture might still be thick. If
this happens, add enough water.
5.
Using the forceps, retrieve the magnetic stirring bar from the mixture. Take a
closer look at the magnetic stirring bar.
Q1. Do you notice anything that clings to the magnetic stirring bar?
40
6.
Let the magnetic stirring bar dry. Scrape off whatever has clung to it. Bring a
magnet close to the dried material. Observe what happens.
Q2. What can you infer about the identity of the dried material? What made you say
so?
As you have seen, elements are part of almost anything around us — food,
clothes, rocks, and even this paper you are currently reading from. Elements are said
to be the building blocks of matter. They are like blocks that you can put together and
build something new. When you build something new from these elements, you call
them as compounds.
Compounds are made up of elements. Elements are the
simplest form of matter. Both elements and compounds
are substances.
With the 118 elements, imagine how many combinations of elements you can
make into compounds and how diverse the materials around us can be.
In Modules 4 and 5, you will learn more about the compounds and elements.
You will work on different samples of compounds and elements and explore their
properties.
41
Suggested time allotment: 5 to 6 hours
Unit 1
MODULE
4
ACIDS AND BASES
In Module 1, you identified common properties of solutions using different
methods. You learned how to report the amount of the components in a given
volume of solution. You also found out that not all solutions are liquid. Some of them
are solids and others are gases. Towards the end of the module, you investigated
the factors that affect how fast a solid dissolves in water.
In Module 3 you learned about compounds. In Module 4 you will study two
special and important classes of compounds called acids and bases. Examples of
acids are acetic acid in vinegar and citric acid in fruit juices. The solution used for
cleaning toilet bowls and tiles is 10-12% hydrochloric acid. It is commonly called
muriatic acid. These acids in these mixtures make the mixtures acidic. We can say
the same about bases and basic solutions. An example of a base is sodium
hydroxide used in making soaps and drain cleaners. Sodium hydroxide is also called
lye or caustic soda. A common drain cleaner used in most homes in the Philippines
is called sosa. Another base is aluminum hydroxide used in antacids. The bases in
these mixtures make the mixtures basic.
In this module you will investigate the properties of acidic and basic mixtures
using an indicator, a dye that changes into a specific color depending on whether it
is placed in an acidic solution or in a basic one. Aside from knowing the uses of
acidic and basic mixtures, you will also find out the action of acid on metals and think
of ways to reduce the harmful effects of acids. Knowing the properties of acids and
bases will help you practice safety in handling them, not only in this grade level, but
in your future science classes.
How acidic or basic are common household materials?
Does water from different sources have the same acidity?
What is the effect of acid on metals?
42
Activity 1
How can you tell if a mixture is acidic or basic?
How will you know if a mixture is acidic or a basic? In this activity, you will
distinguish between acidic and basic mixtures based on their color reactions to an
indicator. An indicator is a dye that changes into a different color depending on
whether it is in acid or in base. There are many indicators that come from plant
sources. Each indicator dye has one color in an acidic mixture and a different color in
a basic mixture. A common indicator is litmus, a dye taken from the lichen plant.
Litmus turns red in acidic mixtures and becomes blue in basic mixtures.
You will first make your own acid-base indicator from plant indicators
available in your place. This is a colorful activity. You may select a local plant in your
community. You can use any of the following: violet eggplant peel, purple camote
peel, red mayana leaves or violet Baston ni San Jose. These plant materials contain
anthocyanins. These plant pigments produce specific colors in solutions of different
acidity or basicity.
In this activity, you will:
1. Prepare a plant indicator from any of the following plants: violet eggplant
peel, purple camote peel, red mayana leaves or violet Baston ni San
Jose; and
2. Find out if a given sample is acidic or basic using the plant indicator.
TAKE
CARE!
It is dangerous to taste
or touch a solution in
order to decide if it is
acidic or a basic.
Part A. Preparation of Indicator*
In this part of Activity 1, you will prepare a plant indicator that you will use to
determine if a given sample is acidic or a basic.
Materials Needed


1 pc mature, dark violet eggplant or camote leaves of Mayana or Baston ni
San Jose
alum (tawas) powder
*University of the Philippines. National Institute for Science and Mathematics Education
Development (2001). Practical work in high school chemistry: Activities for students.
Quezon City: Author, pp. 29-33.
43





sharp knife or peeler
small casserole or milk can
brown bottle with cover
alcohol lamp
tripod
Procedure
1.
Peel an eggplant as thin as possible. (You may also use the skin of purple
camote or the leaves of red mayana or Baston ni San Jose.)
Cut the materials into small pieces and place in a small casserole or milk can.
You may keep the flesh of the eggplant or camote for other purposes.
2.
Add about ⅓ to ½ cup tap water to the peel depending on the size of the
eggplant or camote used. Boil for 5 minutes. Stir from time to time.
3.
Transfer the mixture into a bottle while it is still hot. There is no need to filter,
just remove the solid portion. The mixture may change if left in open air for more
than 5 minutes.
4.
Immediately add a pinch (2-3 matchstick head size) of alum (tawas) powder into
the solution or until the solution becomes dark blue in color. Stir well while still
hot. This is now the indicator solution.
Note: Alum will stabilize the extract. The extract will be more stable with alum but it is
recommended that the solution be used within a few days. Keep the extract in the
refrigerator or cool dark place when not in use.
Part B. Determining the acidity or basicity of some common household
items
In this part of the activity, you will find out if a given household material is
acidic or basic using the plant indicator you have prepared in Part A.
Materials Needed







plant indicator prepared in Part A
vinegar
distilled water
tap water
baking soda
baking powder
calamansi
44





Other food/home items with no color:
(toothpaste, shampoo, soap, detergent, fruit juice like buko
juice, sugar in water, soft drink)
2 plastic egg trays or 12 small plastic cups or glass bottles
6 droppers
6 plastic teaspoons
stirrer (may be teaspoon, barbecue stick or drinking straw)
Procedure
1.
Place one (1) teaspoon of each sample in each well of the egg tray.
2.
Add 8-10 drops (or ½ teaspoon) of the plant indicator to the first sample.
Note: If the sample is solid, wet a pinch (size of 2-3 match heads) of the solid with
about ½ teaspoon of distilled water.
TAKE
CARE!
3.
Use one dropper for one kind
of sample. Wash each
dropper after one use.
Do not mix samples!
Note the color produced. Record your observations in column 2 of Table 1.
Table 1. Acidic or basic nature of household materials
Sample
calamansi
tap water (water from the
faucet)
distilled water
vinegar
sugar in water
baking soda
baking powder
soft drink (colorless)
coconut water (from buko)
toothpaste
shampoo
soap
4.
Color of indicator
Repeat step number 1 of Part B for the other samples.
45
Nature of sample
5.
Determine the acidic or basic nature of your sample using the color scheme
below for eggplant or camote indicator and record the nature of each sample in
Table 1.
Strongly acidic: red to pale red
Weakly acidic: blue
Weakly basic: green
Strongly basic: yellow
Part C. Determining the acidity or basicity of water from
different sources
In this part of Activity 1, you will find out how acidic or basic the samples of
water from different sources are.
Materials Needed
At least one cup water from each of the following sources of water:











plant indicator prepared in Part A
rainwater
river, lake or stream
pond
canal
faucet
deep well or hand pump
bottled water (mineral water) or distilled water
2 plastic egg trays or 8 small plastic containers
6 droppers
6 plastic teaspoons
Procedure
1.
Place one (1) teaspoon of each sample in each well of the egg tray.
2.
Add 8-10 drops (or ½ teaspoon) of the plant indicator to the first sample.
Note: If the sample is solid, wet a pinch (size of 2-3 match heads) of the solid with
about ½ teaspoon of distilled water.
TAKE
CARE!
Use one dropper for one
kind of sample.
Wash each dropper after
one use.
Do not mix samples!
46
3.
Note the color produced. Record your observations in column 2 of Table 2.
Table 2. Acidic or basic nature of water from different sources
Water sample from source
Color of indicator
Nature of sample
rainwater
river, lake or stream
Pond
Canal
water from faucet
4.
Determine the acidic or basic nature of your sample using the color scheme
below for eggplant or camote indicator and record the nature of each sample in
Table 2.
Strongly acidic: red to pale red
Weakly acidic: blue
Weakly basic: green
Strongly basic: yellow
You can now operationally distinguish between acidic and basic mixtures
using plant indicators. More than that, using the plant extract you have prepared
allowed you to further determine the degree of acidity or basicity of a mixture, that is,
you were able to find out how strongly acidic or basic the mixtures were.
Another method can be used to indicate the acidity or basicity of mixtures. It
is through the use of the pH scale, which extends from 0 to 14. The pH scale was
proposed by the Danish biochemist S.P.L. Sorensen. In this scale, a sample with pH
7 is neutral. An acidic mixture has a pH that is less than 7. A basic mixture has a pH
that is greater than 7. In general, the lower the pH, the more acidic the mixture and
the higher the pH, the more basic is the mixture.
It is useful for you to know the pH of some samples of matter as shown in
Table 3 and illustrated in the pH scale drawn in Figure 1.
47
Table 3. Approximate pH values of some samples of matter
Sample of Matter
Gastric juice
Lemon juice
Vinegar
Soft drinks
Urine
Rainwater (unpolluted)
Milk
Saliva
Pure water
Blood
Fresh egg white
Seawater
Laundry detergents
Household bleach
Drain cleaner
pH
1.6-1.8
2.1-2.3
2.4-3.4
2.0-4.0
5.5-7.0
5.6
6.3-6.6
6.2-7.4
7.0
7.35-7.45
7.6-8.0
8.4
11
12.8
13.0
Figure 1. The pH values of some samples of matter.
48
Activity 2
Color range, pH scale!
In this activity, you will use the results in Activity 1, Parts B and C, to
determine the pH of the solutions you tested. Use the following pH scale for eggplant
indicator to determine the pH of the common mixtures you tested in Activity 1.
Present your results in a table similar to Table 4.
The eggplant indicator shows the following color changes.
pH 1
2
red/
3
4
pale/
red
5
6
blue
ACIDIC
becoming more acidic
7
8
9
10
/green
11 12 13
/yellow
14
BASIC
N
E
U
T
R
A
L
becoming more basic
Table 4. pH of samples from Activity 1
Sample
pH based on eggplant/camote
indicator
Acidic or Basic
Now that you are aware of the pH of some common mixtures, why do you
think is it important to know about pH? The following facts give you some information
on how pH affects processes in the body and in the environment, as well as in some
products you often use.
49
Importance of pH
pH and the Human Body
Acids and bases perform specific functions to balance the pH levels in the
body. When your body has too much carbon dioxide, the blood becomes too acidic.
You breathe slowly. Breathing is slowed to increase the pH in the blood. If pH in the
body is too basic, you will hyperventilate to lower the pH. This acid and base control
is an important part of biological homeostasis (balance) in humans. In fact, human
life is sustained only if the pH of our blood and body tissues is within a small range
near 7.4.
Use of pH in Food Processing and Fruit Preservation
During food processing, pH is closely followed. Changes in pH affect the
growth of microorganisms, which cause food spoilage. Most bacteria grow best at or
near pH 7. To prevent the growth of harmful bacteria, pickling is an effective food
preservation method because it lowers pH.
The control of pH is also needed in wine and jam preparation. A few species
of bacteria grow in a basic medium of pH 9-10. This is the pH range of stale eggs.
Most molds grow within the pH range of 2- 8.5. In acidic conditions, many fruits and
products made from fruits are easily attacked by molds unless the fruits are properly
protected.
Control of pH in Soil
The pH of soil is very important. Some plants grow well in acidic soil while
others prefer basic soil. Farmers need to know the pH of their soil since plants will
only grow in a narrow pH range. The pH also affects how much nutrients from the
soil become available to plants.
The following useful plants in the Philippines grow in acidic soils: banana,
kaimito, durian, pineapple, soybean, coffee, eggplant, squash, kamote, and rice.
Other plants like grapes and pechay require basic soils. Some plants grow best in
almost neutral soil like orange, peanut, watermelon, beans, cabbage, tomato, corn
garlic, and onion.
pH of Rainwater
The average pH of rain is 5.6. This slightly acidic pH is due to the presence of
carbon dioxide in the air. In many areas of the world, rainwater is much more acidic,
sometimes reaching pH 3 or even lower.
Rain with a pH below 5.6 is called “acid rain.” The acidic pollutants in the air
that come from the burning of fuels used in power plants, factories, and vehicles
produce gases which are acidic. These gases enter the atmosphere and dissolve in
50
water vapor in the air. Some acid rain is due to natural pollutants like those from
volcanic eruptions and lightning.
Maintaining pH of Personal Care Products
Most personal care products have pH kept at specific levels to avoid harmful
effects on the body. This is true for hair products. For example, at pH 12, hair
already dissolves, that is why hair removers usually have pH of 11.5 to12. Most
shampoos are within the pH range of 4 to 6. This is because the pH of the product
must be compatible with that of the hair, which is in the range pH 4 to 5. Hair is least
swollen and is strongest at this pH range. But very often, using shampoo leaves the
hair basic. So, in order to avoid eye irritation and stinging, shampoos for infants and
children have a pH similar to that of tears (pH 7.4).
Hair has a protective covering called sebum. The use of conditioners after
using shampoo puts back this oily coating and penetrates the hair shaft itself.
Now that you have discussed with your teacher the importance of keeping the
proper pH in the human body, in food processing and food preservation, in farming
and in personal care products, it is also essential that you know the effects of acids
on some common metals. An important property of acids is their tendency to react
with certain metals. At higher grade levels, you will learn that the nature of the metal
determines how it is affected by specific types of acid. However, in this grade level,
you will simply investigate the effect of an acid on a common metal like iron.
Effect of an Acidic Mixture on Metal
What do you think will happen when an acid and a metal come in contact with
each other? What happens after the metal has been in contact with the acid for
some time? What changes take place?
In Activity 3, you will investigate the effect of an acid on a common metal like
iron. In Module 1, you have learned that vinegar is about 5% acetic acid. You will be
using vinegar in this investigation since it is safe to handle and easily available.
Vinegar will simply be an example that can show the action of an acidic solution
when it comes in contact with a metal. There are other acids that affect metals but
you will learn about them in Grades 8 and 9.
51
Activity 3
What happens to a metal when exposed to an
acidic mixture?
Objective
In this activity, you will find out the effect of an acidic mixture, like vinegar, on
iron.
Materials Needed





3 pieces, small iron nails (about 2.5 cm long)
1 cup white vinegar (with 4.5 to 5 % acidity)
3 small, clear bottles or 100 mL beaker
1 cup water
2 droppers
Procedure
1. Prepare a table similar to the one below.
Setup
After one day
Observations
After 2 days
After 3 days
Iron nail (1)
Iron nail (2)
Iron nail (3)
2.
Clean and wipe dry all the iron nails and the bottles.
3.
Place one piece of the iron nail in each bottle.
Q1. Why do you think are there three different bottles for each sample of iron nail?
4.
Put two to three drops (just enough to barely cover the sample) of vinegar on
top of the iron nail in each bottle.
5.
After adding vinegar to all samples, put aside the bottles where you can
observe changes for three days.
6.
Write your observations after one day, two days, and three days on the data
table in step #1.
52
Q2. At the end of three days, describe completely what happened to each sample.
Q3. Give explanations for the results you have observed.
You have observed the action of vinegar, an acidic mixture, on metal such as
iron in Activity 3. Do you think other types of acidic mixtures act in the same way with
other metals? What about other types of materials? You will learn a lot more about
the action of acids on metal and on different types of materials in Grades 8 and 9.
Safety in Handling Acids and Bases
Now that you know the properties of acidic and basic mixtures, you can
handle them carefully. Acids and bases with high concentrations can cause serious
burns. For example, hydrochloric acid (commonly called muriatic acid) is used in
construction to remove excess mortar from bricks and in the home to remove
hardened deposits from toilet bowls. Concentrated solutions of hydrochloric acid
(about 38%) cause severe burns, but dilute solutions can be used safely in the home
if handled carefully. You can find the following caution in a bottle of muriatic acid:
Harmful or fatal if swallowed. Strong
irritant to eye, skin, and mucous
membrane. Do not take internally.
Avoid contact with eyes, nose and
mouth. Use only in well ventilated areas.
Keep tightly sealed. Do not
store above 60oC. Keep out of reach
of children.
Acidic mixtures can easily “eat away” your skin and can make holes in
clothes. However, since vinegar is only 5% acetic acid, it will not irritate the skin and
destroy clothes.
Sodium hydroxide (commonly called lye or liquid sosa) is used to open
clogged kitchen and toilet pipes, sinks, and drains. Its product label shows the
following warning:
POISON. Avoid contact with any part of
the body. Causes severe eyes and skin
damage and burns. Store in a cool dry
place and locked cabinet. Harmful or fatal
if swallowed.
53
For your safety, you should make it a habit to read product labels before
using them. It is also important to know the proper way of storing these products, as
shown in the label of Liquid Sosa.
What happens when acids and bases combine?
Look back at the pH color chart of Activity 2. You will find a pH value that is
not acidic or basic. Mixtures that are not acidic or basic are called neutral. When an
acid mixes with a base, water and salt are produced. Such a process is called
neutralization.
If a basic mixture is added to an acidic mixture, the resulting mixture will no
longer have the properties of the acidic mixture. In the same way, if enough acidic
mixture is added to a basic mixture, the properties of the basic mixture are changed.
This is because the acid and the base in each of the mixtures neutralize each other
to produce a mixture with a different set of properties.
The process of neutralization has some uses in everyday life. The following
are some examples:

Treating indigestion. The acid in our stomach, gastric juice, is hydrochloric acid
with low concentration. It helps in the digestion of food. If we eat too much food,
the stomach produces more acid which leads to indigestion and pain. To cure
indigestion, the excess acid must be neutralized by tablets called antacids.
These contain bases to neutralize the excess acid in the stomach.

Using toothpaste to avoid tooth decay. Bacteria in the mouth can change
sweet types of food into acid. The acid then attacks the outermost part of the
tooth and leads to tooth decay. Toothpaste contains bases that can neutralize
the acid in the mouth.

Treating soil. You will recall in the earlier part of this module that some plants
grow well in acidic soil while others prefer basic soil. Farmers need to know the
pH of their soil. Most often, the soil gets too acidic. When this happens, the soil is
treated with bases such as quicklime (calcium oxide), slaked lime (calcium
hydroxide) or calcium carbonate. The base is usually spread on the soil by
spraying.

Treating factory waste. Liquid waste from factories often contains acid. If this
waste reaches a river, the acid will kill fish and other living things. This problem
can be prevented by adding slaked lime (calcium hydroxide) to the waste in order
to neutralize it.
After completing this module, you learned about the properties of acidic and
basic mixtures. You can now prepare indicators from plants anytime you need to use
them. You are more aware of the use of the pH scale, which will become more
helpful as you study science in higher grade levels. You now recognize the
54
importance of knowing the acidity or basicity of common mixtures we use, as well as
the relevant uses of the process of neutralization.
References and Links
Brady, J.E. & Senese, F. (2004). Chemistry: Matter and its changes, 4th edition. River
Street Hoboken, NJ: John Wiley & Sons, Inc
Bucat, R.B. (Ed.) (1984). Elements of chemistry: Earth, air, fire & water, Volume 2.
Canberra City, A.C.T., Australia: Australian Academy of Science.
Bucat, R. B. (Ed.) (1983). Elements of chemistry: Earth, air, fire & water, Volume 1.
Canberra City, A.C.T., Australia: Australian Academy of Science.
Burns, R. A. (1999). Fundamentals of chemistry, 3 rd edition. Upper Saddle River,
N.J. Prentice-Hall, Inc.
Elvins, C., Jones, D., Lukins, N., Miskin, J., Ross, B., & Sanders, R. (1990).
Chemistry one: Materials, chemistry in everyday life. Port Melbourne,
Australia: Heinemann Educational Australia.
Gallagher, R. & Ingram, P. (1989). Co-ordinated science: Chemistry. Oxford,
England: Oxford University Press.
Heffner, K. & Dorean, E. (n.d.) Must it rust? The reaction between iron and oxygen.
Retrieved Feb 16, 2012 from
http://www.haverford.edu/educ/knight-booklet/mustitrust.htm
Heyworth, R. M. (2000). Explore your world with science discovery 1. First Lok Yang
Road, Singapore. Pearson Education South Asia Pte Ltd.
Hill, J.W. & Kolb, D.K. (1998). Chemistry for changing times, 8th edition. Upper
Saddle River, NJ: Prentice Hall.
Philippines. Department of Education. (2004). Chemistry: Science and technology
textbook for 3rd year. (Revised ed.). Quezon City: Author.
55
Suggested time allotment: 5 to 6 hours
Unit 1
MODULE
5
METALS AND NONMETALS
Elements are the simplest form of
substances. This means that whatever
you do with an element, it remains to
be the same element. Its physical state
may change but the identity of the
element will not. It may form
compounds with other elements but the
element will never form anything
simpler than it already is.
There are already more than a
hundred elements and are organized in
a Periodic Table. Some of them are
naturally occurring and some were
produced in a laboratory.
In this module, you will find out more about the elements. You will see that
majority of them are metals, while some are nonmetals. In addition to these are the
metalloids, so called because they exhibit properties of both metals and nonmetals.
How are metals different from nonmetals?
How are they similar?
Properties of Metals
In the earlier grades, you segregated objects according to the material they
are made of. You did this when you were starting the habit of 5Rs — recycle, reuse,
recover, repair or reduce. Look around you. Which objects are made of metals?
What made you say that they are metals?
56
Perhaps, you have been identifying a metal based on its appearance. Most of
the time, metals are shiny. They exhibit a luster which is the reason that they are
used as decorations.
Many metals are ductile. This means that metals can be drawn into wires. An
example is copper. The ductility of copper makes it very useful as electrical wires.
Gold is also a metal that is ductile; however, it is rarely used as an electrical wire.
What could be the reason for this?
Some metals are malleable. This means that they can be hammered or
rolled into thin sheets without breaking. An example is aluminum. It is passed into
mills and rolled thinly to produce the aluminum foil used to wrap food. Most soda
cans are made of aluminum, too.
Some metals are magnetic. This means that they are attracted by a magnet.
The common ones are iron, nickel and cobalt. Get a magnet. Try them in different
metals in your home or school. Were they all attracted to the magnet? What metals
are these?
The general properties of metals are luster, ductility, malleability and
magnetic properties. Metals exhibit these properties in varying degrees.
Other properties exhibited by metals
In the next activity, you will
investigate the electrical conductivity
of different materials. This property
allows electricity to pass through a
material. You will find out whether this
property is exhibited by metals or
nonmetals. You will use an improvised
conductivity tester as the one shown
on the right.
These are made from copper.
Make sure they are not touching
each other.
Activity 1
Which can conduct electricity, metals or
nonmetals?
Objective
In this activity, you should be able to distinguish between metals and
nonmetals based on its electrical conductivity.
57
Materials Needed



samples of copper, aluminum, sulfur, iron and iodine
white paper
improvised conductivity apparatus
Procedure
1.
Place a sample in a sheet of white paper. This will help you observe the
samples better. In Table 1, note down the appearance of each of them.
Table 1. Electrical conductivity of different materials
Sample
Appearance
Electrical Conductivity
aluminum
copper
iodine
iron
sulfur
Q1. Which of the samples look like metals? How about nonmetals?
2.
Place the end tip of the improvised conductivity apparatus in contact with each
sample. If the tester gives off a sound, the sample is said to be electrically
conductive. Otherwise, it is electrically nonconductive.
Note: Do not let the end tips of the conductivity tester touch each other.
Q2. Which of the samples are electrical conductors? Which are not? Note them
down in Table 1.
In the activity above, you determined qualitatively
the electrical conductivity of each sample. However, if you
wish to know the electrical conductivity values, a more
sophisticated tester may be used such as the one in the
figure below.
The metallic probe in the figure on the left is the one
that comes in contact with the sample. It will measure then
display the electrical conductivity value in the liquid crystal
display (LCD) screen. Refer to the periodic table found at
the end of this unit.
58
The electrical conductivity values are written at the bottom line of each box. It
is expressed in x106 Ohm-1cm-1. What do you notice about the elements with
electrical conductivity values? Where are they located in the periodic table?
One amazing feature of the periodic table is
that all the metals are placed in one side. Those
that are on the other side (grayish shade) are the
nonmetals.
Notice that there is a stair step line
formed by some elements which somewhat
divides the metals and nonmetals. These
elements are the metalloids. They are
elements exhibiting properties that are
intermediate to metals and nonmetals. Name the
metalloids. Name some metals. Name some
nonmetals.
Which are electrically conductive, metals or nonmetals? Which element has
the highest electrical conductivity value? What could be the reason for using copper
as an electrical wire more than this element?
You might wonder why some metals do not have electrical conductivity
values when supposedly all of them possess such property. Notice that these metals
are the ones mostly found at the last rows of the periodic table. Elements in those
rows are mostly radioactive. This means that the element is very unstable and exists
in a very short period of time. In effect, it would be difficult to test for their properties.
In the higher grade levels, you will learn that there are ways to infer the electrical
conductivities of these elements.
Electrical conductivity clearly distinguishes metals from nonmetals but there is
one exception. Refer to the periodic table. Which element is electrically conductive
even if it is a nonmetal?
One form of carbon is graphite. It is commonly available as
the black rod in your pencils. Get your sharpened pencil. Place the
black rod in between the end tips of your improvised conductivity
tester. Make sure that the black rod is in contact with the tips of the
tester. What happened?
In the higher grade levels, you will learn why carbon (graphite)
though a nonmetal is electrically conductive.
Look for other objects and test if they are made up of metal or nonmetal.
Write down these objects in the appropriate box of the diagram below.
59
Were you able to find a
cooking pot as one of your test
objects? What element is it mainly
made of?
Refer to Table 2. This table
shows the thermal conductivity values
of some elements expressed in
Watt/centimeter-Kelvin
(W/cmK).
Thermal conductivity is the ability of
an element to allow heat to pass
through it. The higher the value, the
better heat conductor an element is.
Find the elements that are mainly
used for the cooking pots. What can
you
say
about
the
thermal
conductivity of this element compared with the other elements? Is this element, a
metal or nonmetal? In general, which are better heat conductors, metals or
nonmetals? Based on Table 2, what other elements can be used as cooking pots?
Note as well that the malleability of a metal is a consideration in using it as a material
for cooking pot.
Table 2. Thermal conductivities of some elements
Element
Copper
Aluminum
Iron
Selenium
Sulfur
Phosphorus
Symbol
Cu
Al
Fe
Se
S
P
Thermal Conductivity* (W/cmK)
4.01
2.37
0.802
0.0204
0.00269
0.00235
*Kenneth Barbalace. Periodic Table of Elements - Sorted by Thermal Conductivity.
EnvironmentalChemistry.com. 1995 - 2012. Accessed on-line: 3/14/2012
http://EnvironmentalChemistry.com/yogi/periodic/thermal.html
Metals and Nonmetals In and Around You
In the figure below, you will find the elements that your body is made up of.
What element are you made up of the most? Is it a metal or a nonmetal? Of all the
elements reported in the graph, how many are metals? How about nonmetals?
60
Data taken from Burns, 1999
Refer to the figure on the next page. The figure shows how much of one
element is present in the Earth’s crust relative to the other elements. What element is
the most abundant in the Earth’s crust? What comes second? Are these metals or
nonmetals?
Data taken from Burns, 1999
61
Refer to the periodic table. What constitutes majority of the elements, metals
or nonmetals?
Interestingly, even with the fewer number of nonmetals, their abundance is
higher than metals. As you have seen above from the two graphs, both living and
nonliving systems are mainly composed of nonmetals.
As you learned in Module 3, elements form compounds. The percentage
abundance of the elements reported in the graphs above accounts some elements
that are present in compounds, much like the food ingredients you encountered in
Module 3. For instance, sodium is present in sodium chloride. The 18.0% carbon that
makes up the human body is mostly compounds of carbon such as the DNA that
carries your genetic code.
Oxides of Metals and Nonmetals
Similarly, oxygen accounted in the graphs may also be in compounds. Some
of these compounds are called oxides. These oxides may be formed when an
element is burned. These oxides exhibit different acidities. In Module 4, you learned
that there are indicators that you can use to determine such. One of these acid
indicators is the litmus paper. What color does the litmus paper show when the
sample is acidic? How about when the sample is basic?
In the next activity, you will separately burn a sample of a metal and a
nonmetal. You will test the acidity of the oxide of a metal and that of the oxide of a
nonmetal.
Activity 2
Acidity of the oxides of metals and nonmetals
Objective
In this activity, you should be able to distinguish between metals and
nonmetals based on the acidity of their oxides.
Materials Needed








magnesium (Mg) ribbon
sulfur (S)
iron wire (holder)
alcohol lamp
test tube
beaker
litmus paper (red and blue)
water
62



cork
watch glass
dropper/stirring rod
Procedure
1.
Get a piece of iron wire. Make a small loop at one end. Insert the other end into
a cork to serve as a handle.
2.
Get a piece of magnesium ribbon. Describe its appearance. Note this in Table
3.
Q1. Is magnesium a metal or a nonmetal?
3.
Coil a small piece of Mg ribbon
(about 2 cm) and place on top of
the loop. Place the looped end of
the wire into the flame of an
alcohol lamp. Note what happens.
Record your observations in Table 3.
TAKE
CARE!
Do not inhale the
fumes/vapor.
4.
Place 2 mL of water in a small test tube. Add the ash produced when you
burned the Mg ribbon. Shake the test tube gently.
5.
Get a watch glass and place a piece each of red and blue litmus papers.
6.
Wet one end of a stirring rod with the solution and place a drop of this solution
on a piece of blue litmus paper. Repeat the test on red litmus paper.
Q2. Which litmus paper changed in color? Describe the change. Note this in Table 3.
Q3. Is the oxide of magnesium acidic or basic?
7.
Place 2 mL of water in another test tube. Clean the wire loop and dip in
powdered sulfur (S).
Q4. Is sulfur a metal or nonmetal?
8.
Place the looped end of the wire containing the sample over the flame. As soon
as the sulfur starts to burn, put the loop into the test tube without touching the
water. Remove the loop into the test tube once the sulfur is completely burned.
Cover the test tube immediately and shake well.
9.
Get a watch glass and place a piece each of red and blue litmus papers.
10.
Wet one end of a stirring rod with the solution and place a drop of this solution
on a piece of blue litmus paper. Repeat the test on red litmus paper.
Q5. Which litmus paper changed in color? Describe the change. Note this in Table 3.
63
Q6. Is the oxide of sulfur acidic or basic?
Table 3. Data for Activity 2
Observations
Before
heating
During
heating
After heating
Reaction of its
oxide with
litmus paper
Magnesium
(Mg)
Sulfur
(S)
In this module, you learned about the properties of metals and nonmetals.
These properties are the ones that determine their uses like aluminum’s malleability
to become soda cans, and copper’s ductility to become electrical wires.
Most of the elements are metals. They are shiny, malleable and ductile but
just in varying degrees – like electrical and thermal conductivity. Nonmetals
are electrically nonconductive except for some forms of carbon.
It is important to note though that most objects are made not of a single
material, rather of a combination of materials so they become fitter for a purpose.
This is where your knowledge on the properties of materials comes in. Which
materials do you combine to make it fit for a purpose? As you can see from the
image in this module cover, the electrical wire made of copper was covered with
rubber. Rubber is mainly made of compounds of nonmetals such as carbon,
hydrogen and chlorine. As you have learned, nonmetals are nonconductors of
electricity. Using a nonmetal to cover a metal makes it safer to use as an electrical
wire.
As you advance to another grade level, there are more properties of matter
that you will encounter. It is hoped that you will be able to maximize the properties of
different materials to create new beneficial products or find other uses for them.
64
PERIODIC TABLE
65
OF ELEMENTS
66
67
Suggested time allotment: 4 hours
Unit 2
MODULE
1
FROM CELL TO ORGANISM
Overview
There are different materials in the environment. There are also diverse
kinds of living things. This module will discuss different kinds of living things and
what they are made up of.
Organ systems work together to help organisms meet their basic needs and
to survive. The digestive system helps organisms get energy from the food they eat.
The circulatory system moves the nutrients that come from digested food, along with
blood, to the different parts of the body. How do you think do the other organ
systems work together? Do plants have organ systems, too?
Organ systems are made up of organs that have related functions and are
grouped together. For example, the mouth, esophagus, stomach, and intestines are
organs of the digestive system. The heart, arteries and veins are some parts that
make up the circulatory system. Are there organisms that do not have organs?
This module introduces you to the different structures that make up an
organism. These structures are formed from the grouping together of parts whose
functions are related. You will also discover in this module that organs themselves
are made up of even smaller parts. Anything that happens to these small parts will
affect the functioning of the organs, organ systems, and the whole organism.
What are organisms? What makes them up?
Activity 1
What makes up an organism?
Objectives
In this activity, you should be able to:
1.
identify the parts that make up an organism,
68
2.
3.
describe the function of each part, and
describe how these parts work together in an organism.
Materials Needed


Writing materials
Posters and pictures of organisms, organ systems, organs, tissues, and
cells
Procedure
Read the selection below and answer the questions that follow.
You are an organism just like the plants and animals.
Photos: Courtesy of Michael Anthony B. Mantala
Figure 1. Pictures of a human being, plant, and an animal
Have you ever asked yourself what makes you
up and the other organisms around you? Figure 2 shows
a model of a human torso.
Q1. What parts of the human body do you see?
Q2. To which organ systems do these parts belong?
Figure 3 shows two other organ systems that you
may be familiar with.
Photo: Courtesy of Michael Anthony B. Mantala
Biology Laboratory, UP NISMED
Figure 2. A model of a human torso
69
Q3. Can you identify these organ systems?
Q4. How do these organ systems work together?
Figure 3. Other Organ Systems
The circulatory system is one of the organ
systems that make up an organism. It is made up of the
heart, blood vessels, and blood.
Figure 4 shows a model of a human heart. Your
heart is about the size of your fist. It pumps and
circulates blood to the different parts of the body through
the blood vessels.
Certain diseases affect the heart and cause it to
function improperly. To learn more about these diseases
and what they do to the heart, interview relatives or
neighbors who have heart problems or who know of
people who have the disease. You can also use the
internet and the library to read articles about how certain
diseases affect the heart, its parts, and the whole
organism.
Q5. Refer to Figure 4. What parts of the human heart
do you see?
70
Photo: Courtesy of Michael Anthony
B. Mantala, Biology Laboratory, UP
NISMED
Figure 4. A model of a
human heart
Q6. What do you think will happen to the heart if any of these parts were injured or
diseased?
Q7. If these parts of the heart were injured or diseased, what do you think will
happen to the organism?
The excretory system is another organ system
that makes up an organism. It is made up of different
organs that help the body eliminate metabolic wastes
and maintain internal balance. These organs include a
pair of kidneys. Figure 5 shows a model of a human
kidney. What shape does it look like?
The kidneys are made up of even smaller parts.
Some parts eliminate wastes that are no longer needed
by the body; other parts function in the reabsorption of
water and nutrients.
Like the heart, certain diseases also affect the
kidneys and their function. To learn more about these
diseases and what they do to the kidneys, interview
relatives or neighbors who have kidney problems or who
know of people who have the disease. You can also use
the internet and library resources to read articles or
news clips about how certain diseases affect the kidneys
Photo: Courtesy of Michael Anthony
B. Mantala, Biology Laboratory,
UP NISMED
Figure 5. A model of a
human kidney
– and the other organs of the body – and the whole organism.
Q8. Refer to Figure 5. What parts of the human kidney do you see?
Q9. What do you think will happen to the kidneys if any of these parts were injured
or diseased?
Q10.
If these parts of the kidneys were injured or diseased, what do you think will
happen to the organism?
Q11.
What procedure can a medical doctor do to
correct an injury to these organs?
Organs are made up of tissues. The heart,
kidneys, and the parts that make them up are
made up of tissues. Figure 6 shows a picture of a
muscle tissue. This tissue is made up of cells - the
basic units of structure and function in organisms.
Photo: http://www.uoguelph.ca/zoology/
devobio/miller/013638fig6-17.gif
Figure 6. Muscle tissues
71
Q12.
What do you think will happen to the organs if these tissues were injured or
diseased?
Q13.
If these tissues were injured or diseased, what do you think will happen to the
organ systems?
Q14.
If these tissues were injured or diseased, what do you think will happen to the
organism?
Plants are also made up of organ
systems: the root and shoot systems. The root
system absorbs water and nutrients; the shoot
system moves them to the different parts of the
plant.
Q15.
Q16.
In what ways are the functions of the
organ systems of plants similar to those of
animals?
Photo: Courtesy of Michael Anthony B. Mantala
Figure 7. An orchid showing
shoot and root systems
In what ways are they different?
Figure 8 shows a picture of a flower.
Flowers are the reproductive organs of plants.
Together with the leaves and the stems, they
make up the shoot system.
Q17. In what ways are flowers similar to the
reproductive organs of animals?
Photo: Courtesy of Michael Anthony B. Mantala
Q18.
In what ways are they different?
Q19.
How do the flowers, leaves, and stems
help plants meet their basic needs?
Q20.
What do think will happen to the plant if any of the parts that make up the
shoot system were injured or diseased?
Figure 8. A Gumamela
(Hibiscus) flower
Figure 9 shows a picture of the roots of a
tree. What parts do you think make up these
roots?
Q21.
Aside from absorbing water and nutrients,
what other functions do the roots serve?
Photo: Courtesy of Michael Anthony B. Mantala
Figure 9. Roots of a tree
72
Figure 10 shows a model of a section of a root
tip. When you get a small section of a root tip and view
it under a microscope, you will see that it is made up of
many layers of tissues. You will also see that these
tissues are composed of similar cells that are arranged
and grouped together to perform specific functions.
Q22.
What do you think will happen to the roots if the
tissues that make them up were injured or
diseased?
Q23.
If the roots were injured or diseased, what do
you think will happen to the plant?
Photo: Courtesy of Michael Anthony B. Mantala
Biology Laboratory, UP NISMED
Figure 10. A model of a
section of a root tip
showing different plant
tissues
Take a closer look at the models of
animal and plant cells in Figure 11. Cells are
the basic units of structure and function of all
organisms. These cells are grouped together to
form more complex structures: tissues, organs,
and organs systems.
Animals and plants are very different
organisms and yet, they are both made up of
parts that are organized similarly.
Photo: Courtesy of Michael Anthony B.
Mantala, Biology Laboratory, UP NISMED
Figure 11. Models of animal
and plant cells
Q24.
What do you think will happen to the tissues, organs, and organ systems if
these cells were injured or diseased?
Q25.
If the tissues, organs, and organ systems were injured or diseased, what do
you think will happen to the organism?
73
Activity 2
Levels of organization in an organism
Objectives
In this activity, you should be able to:
1.
identify the different levels of organization in an organism,
2.
describe the parts that make up each level of organization and their
functions, and
3.
describe how the parts that make up a level of organization affect the
higher levels of organization and the entire organism.
Materials Needed


Writing materials
Posters and pictures of organisms, organ systems, organs, tissues, and
cells
Procedure
1.
From the interviews you have made in Activity 1 and the articles you have read
about certain diseases that affect the heart, kidneys, and the other parts of the
body, complete the table on page 8. You may use Manila paper if the spaces
provided in the table are not enough.
2.
On the topmost row write a disease, which you have read about or learned
from your interview, that affects parts of the human body.
3.
In each of the boxes that correspond to the levels of organization, describe how
the disease affects the parts that make up each level.
4.
Opposite each level of organization, cut and paste pictures (you may use the
pictures that come with the articles) that show how the disease affects the parts
that make up the different levels. Another option is to show it through drawing.
74
Table. Diseases and their effects on the levels of organization in an organism
Disease:
How does the disease affect
each of the following levels of
organization?
Pictures/Drawings
Organism
Organ System
Organ
Tissue
Cell
After learning the different levels of organization in organisms, can you think
of levels of organization that are bigger than the organism?
75
Try this!
Complete this graphic organizer with pictures!
Humans and
animals are
organisms...
Plants are organisms...
Humans and animals are made
up of organ systems...
Plants are made up of organ
systems...
Organ systems are
made up of organs...
Organ systems are
made up of organs...
Organs are made up of
tissues...
Organs are made up of
tissues...
Tissues are made up of cells... All
organisms are made up of cells.
76
Reading Materials/Links/Websites
Bright Hub Education. (2009). Science lesson plan: Biological organization. Middle
School Science Lessons. Retrieved from http://www.brighthubeducation.com/
Education. (2003). The Pyramid of Life (Levels of Biological Organization). Biology
demystified: A self-teaching guide. Retrieved from http://www.education.com/
Scitable by Nature Education. (2008). Biological complexity and integrative levels of
organization. Scitable Topicpage. Retrieved from
http://www.nature.com/scitable
77
Suggested time allotment: 4 to 5 hours
Unit 2
MODULE
2
PLANT AND ANIMAL CELLS
Overview
All organisms, big or small consist of cells. Some organisms are singlecelled, composed of only one cell. Others are multicellular, possessing many cells
that work together to form an organism. The moss plant for example, may be made
up of hundreds or thousands cells. Your body has billions of cells while very large
animals like elephants have trillions.
Most cells are so small that they can only be seen using the microscope. It
is a special equipment to make small objects like cells look bigger. One kind of
microscope used to study cells is called a light microscope. Light microscopes use
diffused or artificial light to illuminate the object to be observed. From the simplest to
the most powerful and sophisticated microscopes, scientists were able to gather
information about cells. What you will see and learn about cells later have been
revealed by microscopes. If your school has microscope, your teacher will teach you
how to use it through activities you will perform.
In this module you will study plant and animal cells, their parts and functions.
Are all cells the same?
If not, in what ways are they different?
Cell Parts
Use the illustrations that follow to learn about parts of plant and animal cells.
78
Activity 1
Comparing plant and animal cells
Objectives
After doing this activity, you should be able to:
1.
2.
3.
4.
identify parts of the cell;
describe plant and animal cells;
differentiate plant cells from animal cells;
construct a Venn Diagram to show parts that are common to both and parts
that are only found in either plant or animal cells.
Materials Needed



sheet of paper
ballpen or pencil
Illustrations in Figures 1 and 2
Procedure
1. Study closely Figures 1 and 2. These are diagrammatic presentations of plant
and animal cells and their parts.
Figure 1. Parts of a plant cell
79
Figure 2. Parts of an animal cell
Q1. Compare the shape of a plant cell with that of an animal cell as shown in
Figures 1 and 2.
Q2. Which cell parts are found in both cells?
Q3. Which are present only in animal cells?
Q4. Which are present only in plant cells?
A Venn Diagram shows relationships between and among sets or groups of
objects that have something in common. It uses two circles that overlap with one
another. The common things are found in the overlapping area, while the differences
are in the non-overlapping areas.
2. Using the information you have gathered from Figures 1 and 2, construct a Venn
diagram of plant and animal cells on a sheet of paper. Label the overlapping and
non-overlapping areas.
3. Present and explain your Venn diagram to class.
Q5. Based on your observations and study of plant and animal cells, cite
differences and similarities between them.
80
A cell has three basic parts: the nucleus, plasma membrane and cytoplasm.
The nucleus is a part of cells which is easily seen. It is very important because it
controls all the activities of the other parts that occur within the cell. The nucleus
contains materials that play a role in heredity. You will discuss about these materials
in the later modules and grade levels.
The plasma membrane encloses the cell and separates what is inside it
from its environment. It also controls what goes into and out of the cell. The plasma
membrane allows entry of materials needed by the cell and eliminates those which
are not needed.
Q6. What do you think will happen to the cell if the plasma membrane does not
function properly?
The cytoplasm consists of a jelly-like substance where all the other parts of
the cell are located. It does not however, include the area where the nucleus is
located. Many different activities of the cell occur in the cytoplasm.
You have seen that plant cells have cell walls and chloroplasts that are not
found in animal cells. The cell wall is made of stiff material that forms the outermost
part of plant cells. This gives shape and protection to them.
Recall in your elementary grades that plants make their own food.
Chloroplasts are important in plant cells because it is where food is made. It contains
chlorophyll, a green pigment, which absorbs energy from the sun to make food for
plants.
Q7. What is the purpose of the cell wall in plants?
Q8. Look at Figure 1 again. Why are there several chloroplasts in the plant cell?
Vacuoles are present in both plant and animal cells. In plant cells, they are
large and usually occupy more than half of the cell space. They play a role in storing
nutrients and increasing cell size during growth. Some plant vacuoles contain
poisonous substances. Vacuoles also store water, thereby maintaining rigidity to
cells and provide support for plants to stand upright. Plant cell vacuoles are
responsible for the crisp appearance of fresh vegetables.
Vacuoles in animal cells are small and are called vesicles. They serve as
storage of water and food and also function in the excretion of waste materials.
Q9. How would vacuoles in plants serve as defense against animals that eat them?
You have observed that centrioles are only found in animal cells. These
have a role in cell reproduction which you will take up in Grade 8.
81
You have been introduced to the basic parts of plant and animal cells. Your
teacher will discuss the functions of the mitochondrion, golgi body, endoplasmic
reticulum (rough and smooth), lysosomes and ribosomes.
If you have a microscope you can also study plant cells by doing the next
activity. Read and do the activities in the section on “How to Use The Light
Microscope” before performing Activity 2.
Activity 2
Investigating plant cells
Objectives
In this activity, you should be able to:
1.
2.
3.
4.
5.
6.
prepare a wet mount;
describe a plant cell observed under the light microscope;
stain plant cells;
identify observable parts of a plant cell;
draw onion cells as seen through the light microscope; and
explain the role of microscopes in cell study.
Materials Needed
 dropper









cover slip
glass slide
onion bulb scale
scalpel or sharp blade
tissue paper
iodine solution
light microscope
forceps or tweezers
50-mL beaker with tap water
Procedure
1.
Prepare the onion scale by following steps indicated in Figure 3. Use the
transparent skin from the inner surface of the onion scale.
Be careful in using the
scalpel or blade!
CAUTION:
82
Figure 3. Preparing onion scale for microscopic study (Source: University
of the Philippines. Institute for Science and Mathematics Education
Development (2000). Sourcebook on practical work for teacher trainers:
High School biology (vol. 2). Quezon City: Science and Mathematics
Education Manpower Project (SMEMDP). p.164)
2.
Following the procedure on how to make a wet mount described in “How to
Use The Light Microscope”, prepare one using the transparent onion skin from
Step 1. Remember to place it on the glass slide with the inner surface (nonwaxy side) facing up. Check too that the onion skin is not folded or wrinkled.
3.
Examine the onion skin slide under the low power objective (LPO).
CAUTION
:
Do not tilt the
microscope!
Q10.
How much are these onion cells magnified?
Q11.
In this case, why is it not good to tilt the microscope?
4.
Shift to the high power objective (HPO).
Raise the objectives a little
and look to the side while
changing objectives!
REMEMBER:
Q12.
Describe the onion cells.
83
5.
Remove the slide from the stage. You can now stain the onion cells with iodine
solution.
IODINE
STAINS!
6.
Be careful not to
spill it on your skin
and clothing!
Using a dropper, place one or two drops of iodine solution along one edge of
the cover slip. Place a piece of tissue paper on the other edge of the cover slip.
The tissue paper will absorb the water, and iodine solution spreads out under
the cover slip until the whole specimen is covered with stain (Figure 4).
Figure 4. Staining onion cells (Source: Philippines. Department of
Education. (2009). Science and Technology II. Textbook (Rev. ed.).
Pasig City: Instructional Materials Development Corporation. p. 23.
7.
Examine the stained onion cells under the LPO and HPO.
Q13.
Did you observe any change in the image of onion cells before and after
staining?
Q14.
How did the iodine solution affect the image of the onion cells?
Q15.
What parts of the onion cell can you identify?
8.
Q16.
Draw three to four onion cells as seen under the HPO. Label the parts you
have identified. Indicate how much the cells are magnified.
Of what importance is the contribution of the microscope in the study of cells?
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You have learned that the cell makes up all organisms. And that organisms
can be made up of just one cell or billions of cells. The module also introduced you to
the microscope which has contributed to the valuable information about cell structure
and function.
You also found out about the fundamental parts of the cell which are the
nucleus, plasma membrane and cytoplasm. These parts play very important roles in
the survival of cells.
Specifically, Activity 1 showed you the similarities and differences in parts of
plant and animal cells and the functions of these parts. Other than the three parts
first mentioned, the mitochondrion, rough and smooth endoplasmic reticulum, Golgi
body, vacuole/vesicle, ribosomes and lysosome are common to them. In fact, these
are also present in fungi and protists which you will study in the next module. You
have observed in the illustrations that plant cells have a cell wall, and chloroplasts
which are not found in animal cells. These have something to do with the nature of
plants having tough stems and their being able to produce their own food. On the
other hand, animal cells have centrioles which are not found in plant cells. You have
seen too the rectangular shape of plant cells as compared to the more or less
rounded one in animal cells shown in the illustrations you have studied. You will
know and see more of the other shapes of plant and animal cells in the next grade
levels.
The second activity was a good opportunity for you to have observed real
plant cells using the light microscope. The use of stains in studying cells has made
cell parts more easy to find, observe and identify.
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Suggested time allotment: 2 to 3 hours
HOW TO USE THE LIGHT
MICROSCOPE
If your school has microscopes read this section and perform the following
activities.
The microscope is a tool which can help you see tiny objects and living
organisms. It makes them look bigger. This ability of the microscope is called its
magnifying power or magnification. The microscope also has the capacity to
distinguish small gaps between two separate points which humans cannot
distinguish. It is called its resolving power or resolution.
The light microscope uses diffused light from the sun or artificial light to
illuminate the object to be observed. From its source, visible light passes through the
small or thin specimen to be observed through the glass lenses. As light passes
through the lenses, it is bent so specimen appears bigger when it is projected to the
eye. The form and structure of the specimen can then be seen because some of
their parts reflect light.
This section will introduce you to the parts of the light microscope and their
functions. More importantly, it will teach you how to use it properly for successful cell
study and other investigations.
What are the parts of the microscope and how does each
part function?
How do you use the microscope?
Objectives
After performing this activity, you should be able to:
1.
2.
3.
4.
5.
handle the microscope properly;
identify the parts of the microscope;
describe what parts of the microscope can do;
prepare materials for microscope study;
focus the microscope properly;
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6.
7.
compare the image of the object seen by the unaided eye and under
the microscope; and
compute for the magnification of objects observed under the
microscope.
Materials Needed










lens paper
light microscope
tissue paper or old t-shirt
newspaper page
glass slide and cover slips
pencil
dropper
scissors
tap water
forceps or tweezer
Procedure
A. The Microscope, Its Parts and their Functions
1. Get the microscope from its box or the cabinet. Do this by grasping the curved
arm with one hand and supporting the base with the other hand.
2. Carry it to your table or working place. Remember to always use both hands
when carrying the microscope.
3. Put the microscope down
gently on the laboratory
table with its arm facing you.
Place it about 7 centimeters
away from the edge of the
table.
4. Wipe with tissue paper or old
t-shirt the metal parts of the
microscope.
Q1. What are the functions of
the base and the arm of the
microscope?
5. Figure 1 shows a light
microscope
that
most
schools have. Study and use
this to locate different parts
of the microscope.
Figure 1. The light microscopes and
its parts
6. Look for the revolving nosepiece. Note that objectives are attached it.
should know that there are lenses inside the objectives.
Q2. What have you observed about the objectives?
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You
Most schools have light microscopes with three objectives. Others have four.
Usually, the shortest one marked 3x, 4x or 5x is called the scanner. The low power
objective (LPO) is marked 10x or 12x while the high power objective (HPO) is
marked 40x, 43x or 60x. The objectives magnify the object to be observed to a
certain size as indicated by the 3x, 10x or 40x, etc. marks.
If the longest objective of your microscope is marked 97x or 100x or OIO or
the word “oil” on it, then it has an oil immersion objective (OIO). This objective is
used to view bacteria, very small protists and fungi. The OIO requires the use of a
special oil such as quality cedarwood oil or cargille’s immersion oil.
7. Find the coarse adjustment. Slowly turn it upwards, then downwards.
Q3. What is accomplished by turning the coarse adjustment upwards? downwards?
8. Looking from the side of the microscope, raise the body tube. Then, turn the
revolving nosepiece in any direction until the LPO is back in position. You will
know an objective is in position when it clicks. Note that the revolving nosepiece
makes possible the changing from one objective to another.
Q4. What is the other function of the revolving nosepiece?
Q5. Which part connects the eyepiece to the revolving nosepiece with the
objectives?
9. Locate the eyepiece. Notice also that it is marked with a number and an x. Know
that the eyepiece further magnifies the image of the object that has been
magnified by the objective. If the eyepiece is cloudy or dusty, wipe it gently with a
piece of lens paper.
REMEMBER:
Only use lens paper in
cleaning the lenses of the
eyepiece and the
objectives.
10.
Look through the eyepiece. Do you see anything?
11.
Now, locate the mirror. Then, position the microscope towards diffused light
from the windows or ceiling light. Look through the eyepiece and with the
concave mirror (with depression) facing up, move it until you see a bright circle
of light.
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Never use direct sunlight as a
light source to view objects
under the microscope. Direct
sunlight can permanently
damage the retina of the eye.
CAUTION:
The bright circle of light is called the field of view of the microscope. Adjust
the position of the mirror so that it is not glaring to the eyes. Practice viewing through
the microscope using both eyes open. This will reduce eyestrain.
Q6. What are the two functions of the eyepiece?
Q7. Describe the function of the mirror.
12.
Locate the diaphragm. While looking into the eyepiece, rotate the diaphragm
to the next opening. Continue to do so until the original opening you used is
back under the hole in the stage.
Q8. What do you notice as you change the diaphragm openings?
Q9. What can you infer as to the function of the diaphragm?
13.
Q10.
14.
Find the inclination joint.
What parts of the microscope are being connected by the inclination joint?
Grasp the arm and slowly pull it towards you. Sit down and try looking through
the eyepiece.
Q11. What does this movement do?
REMEMBER:
Tilting of the microscope allows one
to do observations while seating
down. This is however, only done
when materials observed do not
contain liquids like water.
89
B. Making a Wet Mount
A specimen is a part or sample of any material e.g. plant, animal, paper or
mineral, for study or examination under the microscope. Specimens should be small
and thin for light to pass through them.
15.
Q12.
Cut out a small letter “e” from a newspaper page. Using forceps or tweezers
place it in the center of a glass slide in an upright position.
What makes the letter “e” suitable for
observation under the microscope?
16. Add a drop of tap water over the
specimen. It will act as a mounting
medium and make clear the image of the
specimen. Position the cover slip at 45°
with one side touching one edge of the
water on the slide (Figure 2).
17.
Figure 2. Making a wet mount
Slowly lower the other edge of the cover slip until it rests on the water and the
printed letter. Bubbles are perfect circles you see on your preparation. Remove
or minimize trapped bubbles by gently tapping the cover slip with the eraserend of a pencil. Make the bubble move towards the edge of the cover slip.
C. Observing Specimens
18.
Put the slide on the stage. Make sure that the letter is in the center of the hole
in the stage and under the LPO. Hold it firmly with the stage clips.
19.
Watching from the side, carefully lower the body tube until the end of the LPO
almost touches the cover slip.
20.
Look through the eyepiece. Slowly turn the coarse adjustment upwards to raise
the objective until the letter “e” appears. Continue until you see the letter
clearly. This would indicate that you have focused it already.
Q13.
Describe the position of the letter as seen under the microscope.
Q14.
Compare the image of the letter that you see using your unaided eye with
what you see through the microscope.
21.
Q15.
22.
Look through the microscope again. Slowly move the slide to the right, then to
the left.
To which direction does the image move?
Move the slide to the center. To shift to the HPO, raise the body tube first.
Looking from the side, turn the revolving nosepiece to put the HPO in place.
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Then, using the fine adjustment slowly lower the objective till it almost touches
the cover slip. Looking through the eyepiece, turn the fine adjustment until you
see the clearest image.
Q16.
Why do you have to watch from the side when changing objectives?
Q17.
Why should the fine adjustment knob be used only with the HPO?
Current microscope models are said to be parfocal. This means the image in
clear focus under the low power objective, remains focused after shifting to HPO. If
the microscope you are using is not parfocal, slightly turn the fine adjustment knob in
either direction to get a clear picture.
23. Look through the eyepiece again. Then, shift to the LPO, and the scanner.
Observe closely the image of the letter.
Q18.
In which objective/s can you see the whole letter “e”?
Q19.
What are the advantages of using the HPO? the disadvantages?
Q20.
In which objective is the light darker? brighter?
D. Magnifying Power of the Light Microscope
Can you recall the functions of the objectives and the eyepiece?
The magnification of a specimen can be calculated by multiplying the number
found in the eyepiece with the number found on the objective being used. So, if a
specimen is viewed using a 10x objective and a 10x eyepiece it will be magnified 100
times.
24.
Examine the numbers indicated on the eyepiece and scanner.
Q21.
How much is the letter “e” you are now viewing under the scanner magnified?
under the LPO? Under the HPO?
Q22.
If a cell being observed has been magnified 200x under the HPO, what is the
magnifying power of the eyepiece used?
Q23.
In what ways would the microscope contribute to the study of different objects
and organisms?
25.
After using the microscope, lift the stage clips to remove the slide from the
stage. Wash and wipe or air dry the slide and cover slip. Keep them in their
proper places. Dispose trash or other materials properly.
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You have just familiarized yourself with the light microscope, its parts and
their functions. Similarly, you have practiced using it.
After every use of the microscope, prepare it for storage following these
steps:
1. Turn the revolving nosepiece until the LPO is in place.
2. Lower down the body tube so that the end of the objective is approximately 1
cm above the stage.
3. Position the clips so that they do not extend beyond the sides of the stage.
4. Rotate the diaphragm until the smallest opening is in position.
5. Let the mirror stand on its edge with the concave side facing the user to
protect it from dust.
6. Some microscope boxes have a socket for the eyepiece. In this case, remove
the eyepiece from the body tube and place it in the socket.
7. Put back the microscope’s plastic cover. If the original plastic cover has been
lost or destroyed, use any clean plastic bag big enough to cover the
microscope.
8. Carry the microscope as described in Step 1 of Procedure A. Put it back in its
case or storage cabinet or return it to your teacher.
Knowledge about objects and organisms revealed by the microscope is of
great value not only to students like you but also to everyone who wish to study and
understand life. It is but important for you to know how to take care of this tool for an
efficient and longer use. Here are some practices to achieve this:
1. Check the microscope before and after use. Report any missing or damaged
part to your teacher.
2. Use a clean tissue paper or soft cloth like old t-shirt to clean the mechanical
parts of the microscope.
3. Prevent liquids, especially acids and alcohol from spilling on any part of the
microscope. Always use a cover slip in observing wet mounts.
4. Check for moisture (such as from condensation of human breath) in the
eyepiece. This may happen due to prolonged observation of specimens.
Wipe with lens paper.
5. Avoid tilting the microscope while observing wet mounts. Water might flow
into the mechanical parts of the microscope causing them to rust. Select a
92
chair with suitable height so that both forearms can be rested on the table
during observation.
6. Never store the microscopes in a chemical laboratory or any place where
there are corrosive fumes. Make sure there are silica get packs inside
microscope boxes or storage cabinet to absorb moisture.
The microscope has become an important investigative tool in studying
objects and organisms around you. Knowing its parts as well as proper manipulation
and care will make your study of science effective, interesting and more meaningful.
Reading Materials/Links/Websites
Hwa, K. S., Sao-Ee, G., & Luan, K. S. (2010). My pals are here! 6A science.
(International Ed.). Singapore: Marshall Cavendish.
Miller, K. R., & Levine, L. (2006). Prentice Hall biology. Upper Saddle River, NJ:
Pearson.
Philippines. Department of Education. (2009). Science and Technology II textbook.
(Rev. ed.). Pasig City: Instructional Materials Development Corporation.
Reyes, V.F., & Alfonso, L. G. (1979). The microscope: Part 1. Manila: AlemarPhoenix Publishing House.
http://www.cellsalive.com/cells/cell_model.htm
www.microscope-microscope.org/activities/school/microscope-use.htm
www.biologycorner.com/bio1/microscope.html
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Suggested time allotment: 4 hours
Unit 2
MODULE
3
LIVING THINGS OTHER
THAN PLANTS AND
ANIMALS
Overview
In this module, you will start examining life forms other than the plants and
animals you studied in Grades 3 through 6. You will begin with the macroscopic
forms or parts that you can see and move to the barely noticeable ones, using a
magnifying lens. If your school has a microscope, you can observe the truly
microscopic forms as well. These cannot be seen by the naked eye, not even
through magnifying lenses.
These life forms are in the soil, water and air all around us. They are on our
body and inside it, on the food we eat and the things we use. Many are useful to
humans while some are harmful and may cause disease. In studying them, we
develop inquiry skills and use a powerful observation device, the microscope, if this
is available.
You and your classmates will perform two hands-on activities in this module,
which entail observing, recording, communicating by drawing and writing, going out
in the school grounds to collect specimens, inferring and answering questions.
In so doing, you expand your knowledge about the living world and
appreciate the diversity in life forms.
What are the other living things besides plants and animals?
Which are useful to us? Which are harmful?
Activity 1
Are these also plants?
Objectives
In this activity, you will:
1. observe life forms other than those you studied from Grades 3 through 6,
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2. use a magnifying lens to observe them,
3. share what you know about these life forms with classmates and
groupmates, and
4. compare them with known living things studied in Grades 3 to 6.
Materials Needed


Live specimens from teacher
Magnifying lens
Procedure
1. Look* at the live specimen shown by your
teacher which is like the photo on the right.
Q1. Is it a plant?
Q2. What is its name?
Q3. What is the reason for your answer in Q1?
*Warning: Do not touch the specimen with your bare hands, taste or smell it,
especially those of you who have known allergies and if the
specimen is not eaten. It may be poisonous.
2. Look at the second live specimen your teacher will show you. It is similar to the
photo below:
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Q4.
Q5.
Q6.
Is it a plant?
What is its name?
What is your reason for your answer in Q4?
3. Compare the two specimens shown by your teacher.
Q7.
Q8.
Q9.
Q10.
Q11.
How are they different?
How are they alike?
Do you know of other living things like the two above?
If so, describe these living things.
How did you know about them?
Write their names if you know them.
4. Observe the third specimen to be shown by your teacher. She will show you
something like this photo grabbed from an internet source.
http://www.treeboss.net/tree-trunk-splotches.htm
Q12.
Q13.
Q14.
5.
What do you think it is?
Is it a plant?
Give a reason for your answer in Q13.
Observe these three other things your teacher prepared for you to observe:
a.
b.
Or,
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c.
And, d.
Photo credits: potato by A.
Encarnacion, old banana peeling
and bread by R. Reyes, and
http://www.hawaii.edu/reefalgae
/invasive_algae/chloro/enteromo
rpha_flexuosa.htm downloaded
12 March 2012 for the “green
stuff.”
Warning: Do not touch (a), (b), or (c) with your bare hands. Do not smell or
taste them either. Some sensitive individuals may be allergic to
them.
6. Describe what you see in each (a) and (b) or (c).
Q15.
Q16.
(a)
(b or c)
7. Describe (d).
Q17.
(d)
8. What do you think the growths on (a), and (b) or (c) are?
Q18.
Q19.
(a)
(b) or (c)
9. How about (d), what do you think it is?
Q20.
10.
(d)
Discuss your answers with your classmates and teacher in class.
What you saw are also living things. There are living things or organisms that
cannot be readily identified by the usual parts of plants we recognize like roots,
stems, leaves, flowers, or fruits though they may have the green color and some
plant-like parts. There are also living things that we can see only when we use
magnifying lenses. Tomorrow, we will go out and look for more of these kinds of
living things which are not like the plants we learned about in the lower grades. Bring
plastic gloves and plastic bags at least one each.
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Activity 2
What other living things are found in the school
grounds?
Objectives
In this activity, you will:
1.
2.
3.
4.
5.
6.
7.
8.
hunt for life forms that are doubtfully plants,
collect specimens of these life forms,
observe these life forms using a magnifying lens,
describe/draw them,
describe their habitats,
infer their needs,
compare with others observed in the previous activity, and
group together those that have similarities.
Materials Needed




clear plastic bag
plastic gloves
forceps, tweezers or tongs
magnifying lens
Procedure
1. Bring the first three materials listed when you go out into the school grounds.
Look for other things that are plant-like in the school grounds. Your teacher will
suggest where to go and what to collect.
2. Go back to the classroom and observe what you collected with a magnifying
lens.
Q1.
Describe what you see. Draw it.
Q2.
Describe the place where you found it.
Q3.
Q4.
What do you think it needs to live and grow?
Does it look like any of the organisms you saw yesterday?
If so, which one?
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3. Find out from your teacher the names of all the living things you observed in
Activities 1 and 2.
Q5.
How are they different from the living things you already know about and
studied in the lower grades?
For your homework, find out from reference books and the internet under
which big groups the living things you studied belong. Find out the other members of
these groups, the characteristics they exhibit, their uses to humans, as well as
negative effects. Put the information you collected in a table like the one below:
Name of
organism
Big group/
Other
Examples
Characteristics
Uses/
Benefits
Harmful
Effects
What are the similarities among these groups?
How are they different from each other?
How are these big groups different from the groups of animals and plants studied
in Grades 3-6?
Discuss in class, with your classmates and teacher, the beneficial and
harmful effects of members of these groups.
What you studied in this module are the big groups of Fungi, Algae and
Bacteria which are different from the two big groups of Animals and Plants studied in
Grades 3-6. You did not study many other members of these groups however. There
are many more interesting members of these groups which you will learn about in the
higher grades. Together, these three groups plus the groups of plants and animals
studied in the previous grades make up the living world.
We are a part of this living world. We have to learn to live with different kinds
of living things. Ensuring the survival of other kinds also ensures our own survival.
If your school has a microscope, you can do Activity 3.
It is an OPTIONAL activity.
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Activity 3
What do these living things look like under the
microscope?
Objectives
In this activity, you will:
1.
prepare slides of the growths on old banana peeling, and/or bread mold,
lumot, and the bacterial colony you saw in Activities 1 and 2,
2.
observe these living things using a microscope,
3.
draw and describe these living things, and
4.
be able to label the parts and describe the function of these parts based
on reference photographs or drawings and library/internet research.
Materials Needed





slides and cover slips
dissecting needles (may be improvised)
dropper
cotton, gauze or clean absorbent cloth
clean water
Procedure
1.
Get a small part of the white, cottony growth on the decomposing banana.
2.
Spread it with a needle until only a thin layer is on the middle of the glass slide.
3.
With the dropper, wet the spot with a drop of water.
4.
Cover with the cover slip by putting down one side first and gently laying down
the cover slip until it is flat over the specimen.
5.
Place it on the microscope stage just under the low power objective (LPO).
Q1.
6.
Q2.
Draw what you see.
Focus until clear, then shift to the high power objective (HPO).
Draw what you see.
100
Q3.
Describe what you see under the LPO and HPO.
Q4.
Label the parts based on a reference photo or drawing your teacher shows
you.
7.
Do the same for the growth on the bread, lumot, and Z on the potato.
8.
Discuss your findings with your teacher and classmates.
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Suggested time allotment: 5 to 6 hours
Unit 2
MODULE
4
REPRODUCTION:
THE CONTINUITY OF LIFE
Overview
The beginning of a new life is truly a remarkable event. The sight of a chick
making its way out of the cracked shell or a germinating seed slowly pushing through
the soil can leave one fascinated. The ability of an organism to produce new
individuals is one of the characteristics that distinguishes living things from nonliving
things. This ability is called reproduction.
In the previous modules, you have already begun to explore the diversity of
organisms. These organisms bring about the continuation of their own kind through
reproduction. And although these organisms have different methods of reproduction,
every method leads to the beginning of a new life.
This module will discuss the different modes of reproduction in representative
plants, animals, and microorganisms. Investigations are included in this module to
help you understand the different ways that organisms reproduce and differentiate
the offspring resulting from each mode of reproduction.
What are the different modes of reproduction?
How can we use this knowledge in growing plants?
Modes of Reproduction
In order to continue their own kind, organisms must reproduce. Organisms
may reproduce either asexually or sexually.
I. Asexual Reproduction
There are several ways by which organisms reproduce asexually. In the
following activity, let us examine how potatoes reproduce.
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Activity 1
Can you grow new plants from “eyes”?
A potato tuber is a specialized stem which functions as a food storage organ.
Let us investigate how tubers can be used in growing new plants.
Objectives
After you have performed this activity, you should be able to:
1. describe how potatoes reproduce.
2. explain what vegetative reproduction is.
3. describe the advantages of growing plants using vegetative reproduction.
Materials Needed




1 potato
5 big cans filled with garden soil
(you may use big cans of powdered milk)
trowel
knife
Procedure
potato eye
(bud)
1. Examine the potato. Can
you see depressions?
These are the “eyes” or
buds.
Figure 1. Potato eyes.
2. Cut the potato into pieces with each piece having an “eye”. Observe how the cut
pieces look.
3. Set aside the cut pieces for 2-3 days. Draw and describe how the cut pieces
look after 3 days.
4. After 3 days, plant each piece in a can, about 10-cm deep. Set the tuber so that
the “eye” points upward.
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Q1. Can you give a reason why it is better to plant the cut pieces with the “eye”
pointing upward?
5. Set aside the cans in a shady area. Water the soil everyday to keep it moist.
Q2. How many “eyes” from each potato were you able to get?
Q3. How many new shoots grew from each potato “eye” you planted?
Q4. What is the advantage of using this type of propagation?
6. Report the progress of your work to your teacher. Discuss your work in class.
After this activity, you may transplant the potato plants in your school garden.
You may harvest the potatoes within 10 weeks. Check how many potatoes you can
harvest from one plant.
The activity that you have performed shows how potatoes are propagated
vegetatively. From a single potato, several new potato plants can be produced.
Potato “eyes” are axillary buds where shoots can emerge. Vegetative reproduction
is a kind of asexual reproduction where a new individual, known as the offspring, is
produced from a single parent.
Aside from potatoes, many economically important plants can be propagated
vegetatively. The kalanchoe, a medicinal plant, can reproduce through its leaves
(Figure 2). Plantlets can grow around the leaf margin.
Figure 2. Plantlets grow around the leaf margins of the Kalanchoe.
Do you know other examples of plants that can be propagated through
vegetative reproduction?
In the lower grades, you have learned that during reproduction, certain traits
are passed on from parent to offspring. These traits are in the form of codes
104
contained in genes. Genes are found in chromosomes which are in turn located in
the nucleus of cells.
In asexual reproduction, the parent and the resulting offspring have the same
genes and this is the reason why they have the same traits. In other words, we can
say that they are genetically identical.
Why do we use vegetative propagation to grow plants?
Vegetative
propagation results in plants that reach maturity faster than plants grown from seeds.
Another good thing about vegetative propagation is that the same good agricultural
traits such as taste, yield, and resistance to pests will be passed on from generation
to generation. But one disadvantage is that the population might be wiped out if
environmental conditions become unfavourable.
Let us now look at other types of asexual reproduction.
Activity 2
Can one become two?
While walking to school, have you noticed greenish growth on barks of trees
or on slippery concrete walkways? What could this organism be? Let us observe
closely what organism this might be.
Objectives
After you have performed this activity, you should be able to:
1. describe how Protococcus reproduce.
2. explain what fission is.
3. infer the characteristics of the offspring of Protococcus.
Materials Needed






Scalpel or blade
Microscope slide
Cover slip
Microscope
Tap water in clean bottle
Dropper
Procedure
Preparation for Activity
1. Look for barks of trees, stones, rocks, moist flower pots that have greenish
growth.
2. Get the greenish growth by scraping the sides.
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3. Soak the scrapings in water overnight to separate the soil particles and debris
from the microorganisms.
Day 1
1. Put a small amount of scraping on a slide.
2. Add a drop of water.
3. With 2 dissecting needles, carefully tease or separate the scraping and mix it
with the water.
4. Gently place a cover slip on the slide. Examine the scraping under the low
power objective.
Look for a cell similar to the figure on the right.
5. Show your teacher the Protococcus cell that you have
located.
6. Protococcus reproduces by dividing. Dividing cells
are separated by a wall-like structure. Look for
Protococcus cells that are dividing.
Figure 3. Protococcus
is a round singlecelled green alga.
7. Shift to high power objective.
Q5. Draw the dividing Protococcus cells that you have identified.
This type of asexual reproduction is called fission. The cell divides to form
two identical daughter cells. Each daughter cell continues to grow until it becomes
as large as the parent cell.
Q6. Research on other examples of unicellular organisms that reproduce through
fission.
Budding
Budding is another type of asexual reproduction. Yeast, hydra, and sponges
reproduce this way. Figure 4 shows how yeast, a microorganism used in baking,
reproduces by budding. In budding, a new individual may form as an outgrowth of
the parent. The outgrowth separates from the parent and becomes a new individual.
Figure 4. Budding in yeast.
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Spore Formation
Have you seen a piece of bread with mold
growing on it? The black, round structure at the
tip of a stalk is called a spore case which
contains the spores. When the spore case
opens, the tiny spores are released and may be
carried by wind or water. Once the spore lands
on a favourable environment, it develops into a
new organism. Under the microscope, a bread
mold with a spore case looks like the one in
Figure 5.
spore case
stalk
Figure 5. Bread mold spore case
Formation of spore is another type of asexual reproduction common among
molds or fungi.
Regeneration
Animals can also reproduce by regeneration. Did you know that when a
hydra is cut into several pieces, a process known as fragmentation, each piece can
grow into another hydra? In certain types of starfish, an arm that breaks off from the
body can develop into a new individual.
II.
Sexual Reproduction
Sexual reproduction is a mode of reproduction that involves two parents.
Parents produce reproductive cells called gametes through a type of cell division
called meiosis. Meiosis will be discussed in detail in Grade 8.
Gametes from the two parents unite in a process called fertilization. The
fertilized cell is referred to as a zygote which develops into a new organism.
Organisms reproduce sexually in a number of ways. Let us take a look at
the different ways how representative microorganisms, plants, and animals
reproduce sexually.
Conjugation
Some microorganisms undergo sexual reproduction by a process called
conjugation. An example of a microorganism that reproduces by conjugation is
Spirogyra, a green alga. Spirogyra can be found in freshwater habitats such as
ponds and rivers.
During conjugation, a bridge forms between two cells of two Spirogyra
filaments lying side by side. The contents of one cell pass into the other cell through
the bridge, emptying the other cell. The contents of both cells combine in the other
cell and form the zygote. This zygote is able to secrete a substance that forms a wall
around itself for protection against unfavorable environmental conditions (e.g. when
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the pond dries up). When conditions become suitable for growth and development,
the zygote grows into a new individual.
Sexual Reproduction in Flowering Plants
The flower is the reproductive organ in flowering plants. Flowers have
structures that produce the gametes necessary for reproduction. Let us take a look
at the parts of a gumamela flower.
Activity 3
Structure of a gumamela flower
Objectives
After you have performed this activity, you should be able to:
a)
b)
distinguish the male and the female reproductive structures of a
gumamela flower
describe the function of each structure in reproduction.
Materials Needed


2 gumamela flowers (1 fresh and 1 withered)
1 gumamela bud


Hand lens
Scalpel or Razor blade
Procedure
1. Examine the entire flower and the part of its stem.
Q6.
Describe how the flower is attached to the stem.
2. Examine the bud, an unopened flower. Identify the sepals.
Q7.
What is the function of the sepals in the unopened flower?
3. Remove the sepals and petals. The most important reproductive parts remain.
The innermost part is called the pistil . The pistil has a broad base called the
ovary and a narrow stalk called the style. At the top of the style is the stigma.
Touch the stigma in a relatively fresh opened flower, in a bud and in a withered
one.
Q8.
On which flower does the stigma feel sticky?
Q9.
Why do you think the stigma is sticky?
4. Cut through the ovary and examine the parts with a hand lens.
Q10.
How many compartments do you find?
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Inside the compartments are ovules which contain the egg cell (female gamete).
5. Observe the structures attached to the style. These are the stamens. Touch the
tip of a stamen or tap it lightly over a piece of white paper. The powdery materials
at the tips are made up of pollen grains. Sperm cells (male gamete) are
produced inside these grains.
6. Take a whole flower. Measure the distance between a pollen grain on a stamen
and the ovary where the ovule is.
Q11. How do you think pollen grains reach the pistil?
Pollination brings together the gametes of a flower and it occurs when a
pollen grain of the right kind lands on the stigma of the pistil. Each pollen forms a
tube that grows down through the pistil and reaches the ovule in the ovary. One of
the nuclei in the pollen tube unites with the egg nucleus in the ovule to form a zygote.
The other sperm nucleus combines with another bigger nucleus in the ovule which
develops into the endosperm.
Sexual Reproduction in Humans and Animals
Humans (and all animals that reproduce sexually) have cells called gametes.
Gametes are formed during meiosis and come in the form of sperm (produced by
males) or eggs (produced by females). When conditions are right, sperm and egg
unite in a process known as fertilization. The resulting fertilized egg, or zygote,
contains genes from both parents.
Comparison of Asexual and Sexual Reproduction
In asexual reproduction, a single organism is the sole parent and the
offspring is genetically identical to the parent.
In sexual reproduction, two parents produce offspring that have unique
combinations of genes. Offspring of sexual reproduction differ genetically from their
siblings and both parents.
Summary
1. Organisms must reproduce to continue their own kind.
2. There are two major modes of reproduction: asexual and sexual reproduction.
3. Asexual reproduction gives rise to offspring that are identical to the parent.
4. Individuals that reproduce through sexual reproduction need two parents, a male
and a female, that produce egg cell and sperm cell.
5. Sexual reproduction gives rise to offspring that are a combination of the traits
from its parents.
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Suggested time allotment: 8 hours
Unit 2
MODULE
5
INTERACTIONS
Overview
The environment is a collection of living and nonliving things. Mosses growing
on rocks, garden snails gliding on garden fences, and fish swimming in water are just
a few examples of how living and nonliving things interact. The living components of
the environment are also called organisms. The nonliving components make up the
physical environment of these organisms.
Organisms that belong to the same species and live in the same place form a
population. The moss that grows on rocks makes up a population. Populations that
live in the same place and interact with each other form a community; goats grazing
on grass, chickens feeding on grains, and lizards preying on insects make up a
community.
Interactions between organisms and their environment are also a familiar
sight: carabaos helping farmers till the soil, earthworms burrowing in the ground, and
birds using twigs to build their nests. Organisms interact with each other and their
environment to meet their basic needs and survive.
Some interactions are beneficial; others are harmful. There are also
interactions in which populations of organisms are neither benefitted nor harmed. All
these interactions take place in ecosystems.
In this module, you will discover more about ecosystems, the components
that make them up, and the interactions that take place among the components of
the environment.
How do organisms interact with each other and with their
environment?
How is energy transferred from one organism to the other?
In Module 1, you have been introduced to the concept of levels of
organization in organisms. This module will introduce you to levels of organization
that are beyond the level of the organism.
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Activity 1
What does it mean to be alive?
Objectives
In this activity, you should be able to:
1.
identify the components of the environment,
2.
compare living and nonliving things, and
3.
describe how organisms interact with each other and with their
environment.
Materials Needed



Drawing and writing materials
Rocks whose surface is grown with small plants
Magnifying lens
Procedure
1. Visit your school garden or a pond near your school. On a separate sheet of
paper, describe or draw the place.
Q1. What are the things that you see in your school garden or the pond?
Q2. Which of these things are living? Which of these things are nonliving?
Q3. Observe the things that you identified as living. What do they have in common?
Q4. Observe the things that you identified as nonliving. What do they have in
common?
Q5. What interactions do you observe happening among the living and nonliving
things?
Q6. What makes living things different from
nonliving things?
2. Observe the rocks in your school garden or
the pond near your school. Do they look like
that shown in Figure 1? If so, use a
magnifying lens to see the details of the
Photo: Courtesy of Michael Anthony B. Mantala
small plants. These small plants make
up a population.
Figure 1. Small plants growing on rocks
Q7. What do these small plants need that is provided for by the rock?
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Q8. Where do you find these rocks that are inhabited by small plants?
Q9. What other things in the environment are inhabited by these small plants?
Where do you find these things?
Q10. Why do you find them in these places?
Figure 2 shows a fence populated by
small plants. They usually grow on fences
during the rainy season.
Q11.
Do you also see small plants growing on
the fences of your school?
Q12.
What other living and nonliving things
did you see in the school garden or
the pond? Do you see them in other
parts of the school? Explain your
answer.
Photo: Courtesy of Michael Anthony B. Mantala
Figure 2. Small plants growing on
fences
Figure 3 shows a picture of
populations of different kinds of plants.
Together, they form a community.
Q13.
Do you know of a similar place near
your school where you see
communities of organisms?
Q14.
Are the things you find in your school
garden or the pond the same things
that you find in the backyard of your
house? Explain your answer.
Q15.
Photo: Courtesy of Michael Anthony B. Mantala
Figure 3. Different kinds of plants
How do living things interact with each other and with their environment?
Your environment is home to many kinds of living and nonliving things. You
also see interaction between them like in the rocks and fences that are inhabited by
small plants and algae. These rocks that are usually found in wet places provide
anchorage and nutrients to the small plants and algae.
Activity 2
Housemates? Ecomates!
Objectives
In this activity, you should be able to:
1. describe interdependence among the components of the environment,
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2. explain how organisms interact with their environment to survive, and
3. infer what happens to organisms if their environment is not able to provide
them with their basic needs.
Materials Needed






Eight (8) – 500mL wide-mouthed glass jars with covers
Two (2) liters of water allowed to stand overnight
Hydrilla (or other aquarium plants)
Snails and guppies (or other aquarium fishes)
Light source
Optional: Bromthymol blue solution (BTB) – an indicator that is used to test
for the presence (or absence) of carbon dioxide
Procedure
1. Fill each container with water until it is two thirds full.
Optional: Add 15mL of BTB to each container. Note that this volume of BTB will
depend on the amount of water in the container and how diluted the indicator is.
Setup
A1
B1
C1
D1
1 – With strong light
Water only (control)
Setup
A2
Water with snails and guppies
only
Water with Hydrilla only
B2
Water with snails, guppies,
and Hydrilla
D2
C2
2 – Without light
Water only (control)
Water with snails and guppies
only
Water with Hydrilla only
Water with snails, guppies, and
Hydrilla
3. Use the chart above to set up and label the containers.
4. Cover all the jars.
5. Copy Table 1 on a separate sheet of paper to record your observations of
changes, if any, in the things that were placed in each of the containers.
6. Record data each day for three days. Also include in your data a description of
the health or condition of the organisms and where they stay most of the time in
the container.
Optional: If you use BTB, get a 10 mL sample of water from each container then
add 5 drops of the indicator. Observe for changes in color, if any. Do this each
day for three days.
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Table 1. Interactions among organisms and their environment
Setups
Day 1
Observations
Day 2
Day 3
A1
A2
B1
B2
C1
C2
D1
D2
Q16.
Where did the snails and fish stay most of the time in each of the containers
each day for three days? Explain your answer.
Q17.
What happened to the organisms in each of the containers after three days?
Q18.
In which container/s were the organisms still alive? Which organisms are
these?
Q19.
What do you think will happen to the organisms in each of the jars when left
closed for a longer period of time? Why do you think so?
Questions 19-21 are additional questions if you used BTB.
Q20.
In which container/s did you observe change in color on each day for three
days?
Q21.
Bromthymol blue changes color to yellow in the presence of carbon dioxide.
Which jar/s contained carbon dioxide?
Q22.
What explains the presence of carbon dioxide in this/these container/s?
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Q23.
How do plants and animals depend on each other?
The plants give off oxygen in the presence of light. The fishes and snails
need oxygen to survive. Plants need carbon dioxide given off by the fishes and snails
to survive.
What you observed in this activity are interactions that take place in an
aquarium. There are other kinds of interactions and interdependence among
organisms and their environment in bigger ecosystems.
Ecological Relationships
In the environment, there are plants, animals, and microscopic organisms
such as bacteria and fungi. A group of organisms of the same kind living in the same
place at the same time is called a population.
Q24. In figure 4 below, what populations of organisms do you see?
Photo: Courtesy of Rodolfo S. Treyes
Figure 4. An example of an ecosystem with different organisms
Populations that interact in a given environment form a community. In a
community interactions within and among populations may have important influences
to death rate and birth rates of the organisms and, in turn, on population growth and
size -- these interactions may have positive, neutral, or even negative influences on
interacting populations. Look at figure 5 below. What kind of interaction do the ants
and aphids exhibit?
115
A
B
Figure 5. A. Interacting populations of ants and aphids.
B. An ant may take honeydew from the back of an aphid.
Aphids are small insects that suck liquid containing sugar from the conducting
tissues of plants. These aphids get a certain amount of sugar and other nutrients
from this liquid. However, much of the liquid called honeydew is released through
the aphids’ anus. The ants consume this honeydew as food. The ants, in turn,
protect the aphids from their insect predators. Thus, both species benefit from each
other. This interaction between the populations of ants and aphids is referred to as
mutualism.
Some interactions among organisms are easier to determine than others, and
some effects can easily be observed. Study the photographs that follow.
Figure 6 shows fern plants growing on
a trunk of a Narra tree. What kind of
relationship do you think do these two
organisms have?
Figure 6. Fern plants growing on a trunk
of a Narra tree.
Photo: Courtesy of Rodolfo S. Treyes
Epiphytes are plants that depend on other plants for support. Usually,
epiphytes grow on trunks and branches of trees. Figure 6 shows an epiphytic fern
that attached itself on a trunk of a Narra tree without harming the tree. The Narra
tree is a host that provides a place for the fern to live. When it rains, the ferns get
nutrients from rotting leaves and other organic materials that collect at the root base
of the fern plant. This relationship is called commensalism -- one organism benefits
from the host organism, while the host organism is neither positively nor negatively
affected.
116
Q25. What other examples of commensalism
can you give?
Figure 7 shows an insect larva and a leaf of a
plant. What kind of relationship do you think do
these two organisms have?
Figure 7. A larva of an
insect lives on the leaves
of the plant and causes
damage by eating the
leaves.
Photo: Courtesy of Rodolfo S. Treyes
The insect larva (the parasite) gets its nutrients by eating the leaves –
thereby, damaging the plant (the host). This relationship is called parasitism. A
parasite gets its nutrients from a living host harmed by the interaction. Another
example of parasitism is the flea that thrives on a dog. The dog is harmed by the flea
that feeds on its blood.
Q26. What other examples of parasitism can you give?
Activity 3
Which eats what?
Objectives
In this activity, you should be able to:
1. identify the predators and prey animals in the environment,
2. describe how the predators capture the prey animals for food, and
3. describe how predators and prey animals interact with each other in
the environment.
Materials Needed



worksheet
pencil
hand lens
Procedure
1. Observe each organism in the picture carefully. Fill in the appropriate box to
each of the organism.
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Q27.
Organisms
What
organisms are
involved?
Q28.
Which is the
eater?
Which is eaten?
Q29.
Which part of
the body does
the eater use to
get its food?
2. You may visit a school ground or garden to make more observations.
118
3. If you have observed other organisms that are not in the list, you may also add
such observations to your worksheet. No need to put pictures; just write the
common name of the organisms on the appropriate box.
Organisms
Q30.
Which organisms
are involved?
Q31.
Which is the eater?
Which is eaten?
Q32.
How does the
eater get its
food?
Animals kill and eat other animals. This interaction is called predation. An
animal that kills and eat other animals is called a predator. An animal that is killed
and eaten by its predator is called a prey. Prey animals are usually smaller and less
powerful than the predator that eats them.
In a given community, predators compete with other predators for prey
animals. In the wild, a predator’s prey may be another prey’s predator. This means
that while an animal hunts and feeds upon another animal, it can also become prey
to a larger and stronger predator.
When two populations use the same resource, they participate in a biological
interaction called competition. Resources for which different populations compete
include food, nesting sites, habitat, light, nutrients, and water. Usually, competition
occurs for resources in short supply.
Energy Transfer in the Ecosystems
Why does an organism eat another organism?
Plants, animals, and microorganisms must obtain energy to enable them to
move, grow, repair damaged body parts, and reproduce.
119
Plants are capable of converting energy from the Sun into chemical energy in
the form of glucose (food). The process is called photosynthesis; it uses water,
carbon dioxide, and sunlight. Most plants make much more food each day than they
need. Excess glucose is converted into starch by the plants and is stored either in
the roots, stem, leaves, tubers, seeds, or in fruits, as shown in Figure 8.
Q33. Why are plants considered producers?
Q34. Are plants the only organisms in an ecosystem that can produce their own
food?
rice grains
“petchay”
corn grains
banana
“kamote”
potato
coconut
mango
cassava
sugar cane
Photos: Courtesy of Rodolfo S. Treyes
Figure 8. Different plant parts that store chemical energy in the form of
starch or sugar. Sugar cane is an example of plant with high sugar content.
There are also microorganisms that can photosynthesize; examples of which
are shown in Figure 9.
Spirogyra (algae)
Cyanobacteria (anabaena)
Euglena
Diatoms
Figure 9. These photosynthetic microorganisms are present in ponds, in rice paddies, or
any fresh water ecosystem.
Q35. How do animals and humans obtain energy to keep them alive?
Humans and other animals are not capable of making their own food. They
are dependent on the organic matter made by photosynthetic organisms. These
organisms that include the plants and some microorganisms are considered as
producers.
120
Animals and humans must eat either plants or other animals to obtain energy.
Organisms that feed on other organisms are called consumers. Those that get their
energy by eating plants only are called first order consumers.
Q36.
Q37.
Q38.
In figure 10, which organisms are being eaten?
Which organisms are the consumers?
In your community, what other organisms do you know eat plants only?
Goats eating grass
Cows eating grass
Caterpillar eating
a leaf
Mouse eating corn
Figure 10. The first-order consumers are the animals that eat plants.
Some energy in the first-order consumer is not used by the consumer itself.
This energy is made available to another consumer. A consumer that eats the planteaters for energy is called a second-order consumer, examples of which are shown
in figure 11.
Snake eats corn-eating mouse
Chicken eats caterpillar
Figure 11. The second-order consumers are the animals that eat the
plant-eaters.
Q39.
In figure 11, which organisms provide energy to the snake and chicken?
A second-order consumer gets only a fraction of energy from the first-order
consumer that it fed upon. A part of this energy is stored and may be passed on to
another consumer. A consumer that eats a second-order consumer is called a thirdorder consumer, examples of which are shown in figure 12. Human beings are thirdorder consumers.
121
Figure 12. Third-order
consumers are organisms that
eat the second-order
consumers. (A) A hawk eats a
chicken; and (B) a crocodile
eats a chicken, too.
A
Q40.
B
Refer to figure 13 below. How does energy from the Sun reach the thirdorder consumers? Trace the flow of energy among organisms by filling up
the boxes below. The arrow (
) pointing to the next box means “eaten
by”.
Figure 13. Tracing the flow of energy from the Sun to different organisms.
The transfer of energy can be sequenced. The sequence of energy transfer
among organisms to obtain energy and nutrients is called a food chain (see figure
13). A food chain starts with the energy source, the Sun. The next link in the chain
is the group of organisms that make their own food – the photosynthetic organisms
(producers). Next in the sequence are the organisms that eat the producers; they
are the first-order consumers. The next link in the chain is the group of animals that
eat the first-order consumers; they are the second-order consumers. These
organisms, in turn, are eaten by larger animals – the predators; they are also called,
third-order consumers. Each food chain ends with a top predator – an animal with
no natural enemies.
122
Photos: Courtesy of Grace Reyes
and Rodolfo S. Treyes
Figure 14. A transfer of energy shown in a food chain. The “gabi” plant produces its own food
through photosynthesis. Grasshopper eats the leaves of “gabi” plant to get its energy and
nutrients. The chicken eats the grasshopper. Then the chicken is eaten by humans.
Q41.
List down the organisms found in your community. Classify them according
to the following categories:
Organism
Q42.
Producer
First-Order
Consumer
Second-Order
Consumer
Third-Order
Consumer
Construct a food chain using the organisms listed on the table above.
When plants and animals die, the energy in their bodies can be transferred to
another group of organisms. Consumers that look for and eat dead animals or plants
are considered scavengers.
House flies, cockroaches, maggots and ants are scavengers (see figure 15).
Earthworms feed on dead grass and leaves if they are above ground. They also feed
on fruits, berries, and vegetables. If they are under the soil, earthworms may feed on
algae, fungi, and bacteria.
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Photos: Courtesy of Rodolfo S. Treyes
Figure 15. Common scavengers: housefly, earthworm,
ants, and cockroach.
Once the scavengers are done with eating a dead organism, the
decomposers (microorganisms) take over and consume whatever was left by the
scavengers. Decomposers consume any dead plants and animals.
There are different kinds of decomposers
performing different functions in the ecosystem. Some
groups of bacteria prefer breaking down meat or waste
from the consumers that eat meat.
Figure 16. A group of bacteria.
What do you see on bread or rice that had been kept for some time? They
have molds! Sometimes, you see a trunk of a tree with mushrooms growing on it
(refer to figure 17). These are fungi and they are decomposers; they prefer to grow
on starchy food, fruits, vegetables, and dead plants.
Photos: Courtesy of Rodolfo S. Treyes
Figure 17. Fungi growing on leftover rice and bread, fruit, and dead
trunk of a tree.
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Microorganisms that include bacteria and fungi break down proteins,
starches, and other complex organic substances that were once part of living things.
During the process of decomposition, decomposers release nutrients from the
organic material back into the soil, making the soil available to plants and other
producers.
Activity 4
What to do with food wastes?
At the end of this activity you will decide on the best way to deal with food
wastes in your home or school. You will record your observations and draw
inferences. You will construct food chains starting with the food wastes, which are
actually dead organisms, and the living organisms found in the compost pots. You
will supplement your observations and inferences with information found from the
internet or in the library.
Materials Needed










Two small, clear jars with covers (and with holes all over)
At least three large clay flower pots,
Soil
Rubber gloves
Trowel
Microscope
Slides and cover slips
Magnifying lens
Pole for aerating composting materials
Wire covers for the clay pots
Procedure
1. Set up the composting pots and jars in advance. In one covered jar, put some
food wastes. In the other covered jar, put a layer of soil at the bottom, followed by
a layer of food wastes covered with a layer of soil. Repeat until the jar is full. Do
the same for the clay pots, filling one first before moving to the second pot, until
the third (or last pot) is full. Water the jar and pots with soil if the soil dries up.
2. Do not water the jar of food wastes without soil. Observe the food wastes
and living organisms that you find in the jar daily. Record your observations on a
table like the one below:
125
Day/Date
Observations about food wastes and living organisms
Note: Write your answers on your notebook. Add rows as needed.
3.
Do the same for the jar with soil and the clay pots as soon as they are full.
Include observations about the soil.
4.
After a week, and every week thereafter, mix the contents of a clay pot to
provide air to the organisms underneath the surface the soil.
5.
Continue your observations until the food wastes can no longer be seen and
everything looks like soil. This means that decomposition of the food wastes is
complete or nearly so. You have made compost.
Q43.
What organisms did you find in the compost jar or pot from Day 1? List them
down in the order of appearance. You may draw those you cannot identify.
(Write your answers on your notebook.)
Use the magnifying lens and microscope to examine very small and
microscopic organisms. On Day 1, get small samples of the soil and make wet
mounts to examine it under the microscope. Repeat this after a week and every
week thereafter until the observations are concluded.
Q44.
Draw the microscopic organisms you observe and try to identify them with the
help of reference books.
Q45.
Construct at least one food chain and one food web based on your
observations.
Q46.
What is the benefit of composting food wastes?
Q47.
What other methods would you recommend to dispose of food wastes?
Energy transfer in an ecosystem follows a process. The ultimate source of
energy for all living things is the Sun. The producers of the ecosystem take energy
from sunlight and convert it to chemical energy. This energy is passed on to
consumers and then to decomposers. The energy flows only in one direction and is
not cycled back.
In contrast, the materials in the form of nutrients needed by living things are
cycled between organisms and the environment. These materials are used up by the
producers to make other forms of materials that are cycled among the consumers
and finally returned to the environment by the decomposers. Energy flows and
materials are cycled in the ecosystem. We live in a dynamic world, indeed!
126
Reading Materials/Links/Websites
About Our Earth, Panda. (2008). Ecological interactions. Teacher Resources, Web
Fieldtrips. Retrieved from http://wwf.panda.org/
Global Change, University of Michigan. (2008). Ecological communities: networks of
interacting
species.
Global
Change
Lectures.
Retrieved
from
http://www.globalchange.umich.edu/
Johnson, George B., & Raven, Peter H. Biology. Holt, Rinehart & Winston: A
Harcourt Education Company, U.S.A. 2004
Nature, International Weekly Journal of Science. (2010). Ecological interactions.
Nature Journal. Retrieved from http://www.nature.com/nature/index.html
Reece, Jane B., et al. Campbell Biology: Concepts and Connections, 7 th ed. Pearson
Education Inc., U.S.A. 2012
127
128
129
Suggested time allotment: 8 to 10 hours
Unit 3
MODULE
1
DESCRIBING MOTION
Many of the things around us move. Some move slowly like the turtles and
clouds, others move much more quickly like the satellites. Because motion is so
common, it seems to be very simple. But in science, describing motion actually
entails careful use of some definitions.
This module provides you with scientific knowledge and skills necessary to
describe motion along a straight path. You will learn to describe the motion of objects
in terms of position, distance travelled, and speed. You will also learn to analyze or
represent motion of objects using charts, diagrams, and graphs. While these all
provide the same information about the motion of objects, you will find out that one
may be more helpful than the other depending on your particular objective.
At the end of this module, you are expected to answer the following
questions:
When can we say that an object is in motion?
How do we describe the motion of an object?
Where?
Before you will be able to describe the motion of an object, you must first be
able to tell exactly where it is positioned. Describing exact position entails two ideas:
describing how far the object is from the point of reference and describing its
direction relative to that point of reference. You will learn about the importance of
point of reference and direction when you perform Activity 1.
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Activity 1
Where is it?
Objective
In this activity, you should be able to describe in words the position of an
object within the room or the school ground.
Procedure
1.
Obtain from your teacher the piece of paper that describes where you will find
the object.
Q1. Were you able to find the object? Was it easy or difficult?
Q2. Is the instruction clear and easy to follow? What made it so?
2.
Put back the object to its place, if you found it. Otherwise, ask your teacher first
where it is located before you move on to the next step.
3.
Revise the instruction to make it more helpful. Write it on a separate sheet of
paper and let another group use it to find the object.
Q3. Were they successful in finding the object? Was it easy for them or difficult?
Q4. What other details or information included in your instruction that made it
clearer and easier to follow?
Q5. In your own words, what is point of reference and how important it is?
Describing through visuals
The position of an object can be described in many ways. You can use
words, like what you did in Activity 1. You can also use visuals, like diagrams or
graphs. Use the examples to explore how these help in providing accurate
descriptions of positions of objects.
Using diagrams
Consider the diagram in Figure 1. The positions of the objects are described
in the diagram by their coordinates along the number line.
-15m
-10m
- 5m
0m
Figure 1
131
5m
10m
15m
Q6.
Q7.
Q8.
Q9.
What is the position of the dog?
What is the position of the tree?
What is the position of the dog with respect to the house?
What is the position of the tree with respect to the dog?
Here is another example. In this diagram, the positions of the ball rolling are
shown at equal intervals of time. You can use the diagram to describe the position of
the ball at any given time.
(Timer)
00 : 00
min
00 : 05
sec
min
0m
00 : 10
sec
min
5m
sec
10m
00 : 15
min
sec
15m
Figure 2
Q10. What is the initial position of the ball? What is its final position?
Q11. What is the position of the ball at 10 seconds?
Q12. At what time is the position of the ball equal to 5 meters?
Using graphs
Another way to describe the motion of the ball is by the use of motion graphs.
Convert the diagram in Figure 2 to graph by following the guide below.
I.
Fill up Table 1 using the data in Figure 2. Note that the positions of the ball are
shown every 5 seconds.
Table 1: Position of the ball vs time
Time (s)
0
Position of the ball (m)
0
II. Plot the values in Table 1 as points on the graph in Figure 3. Note that time is
plotted on the X-axis while position is plotted on the Y-axis. An example is given
below.
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Position (m)
15
10
5
(20s, 5m)
0
5
10
15
20
Time (s)
Figure 3
III. Lastly, draw a straight diagonal line through the points in the graph.
The graph that you have just drawn in Figure 3 is called position-time graph.
You can also use this graph to describe the position of the ball at any given time. For
example, if you are asked to find the position of the ball at 10 seconds, all you need
to do is to find the point along the diagonal line where the vertical line at the 10
second-mark intersects (Figure 4). Then find where the horizontal line from that point
of intersection will cross the Y axis, which is the position axis. This will give you the
position of the ball at 10 seconds.
Position (m)
Point of
intersection
0
10
Figure 4
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Time (s)
Now try answering the following questions using your own position-time
graph.
Q13. What is the position of the ball at 7.5 seconds?
Q14. At what time is the position of the ball equal to 12.5 meters?
How Far?
In science, motion is
N
defined as the change in position
W
E
for a particular time interval. You
can then start describing motion
10m
S
5m
with the question, “How far did the
object travel?” There are actually
10m
two ways to answer this question.
First is by getting the total length
of the path travelled by the object.
In Figure 5 for example, the dog
ran 10m to the east, then 5m to
Figure 5
the south, and another 10m to the
west. So it has travelled a total of 25 meters. The other way is by measuring the
distance between the initial position and final position of the object. Based again on
Figure 5, the dog has travelled 5 meters to the south.
In science, the first measurement gives the distance travelled by the object
(represented by broken lines) while the second measurement gives its
displacement (represented by continuous line).
Here are more illustrations showing the difference between distance travelled
(represented by broken lines) by an object and its displacement (represented by
continuous lines).
a.
b.
c.
Figure 6
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Can you give one difference between distance and displacement based on
the given examples? When can displacement be equal to zero? Is it possible to get
zero displacement? What if the ball, the car, and the dog in the illustration go back to
their starting positions, what will happen to their respective distances? How about
their displacements? If you answered these questions correctly, then you have most
probably understood the difference between distance and displacement.


Distance refers to the length of the entire path that the object
travelled.
Displacement refers to the shortest distance between the object’s
two positions, like the distance between its point of origin and its
point of destination, no matter what path it took to get to that
destination.
When a graph is plotted in terms of the distance travelled by the object and
the time it took to cover such distance, the graph can be called distance-time graph.
If the graph is plotted in terms of displacement and time, it is called displacementtime graph. Refer to the graph in Figure 7. What is the displacement of the object
after 2 seconds? What is its displacement after 6 seconds? How will you describe
the motion of the object between 0s and 2s, between 2s and 4s, and between 4s and
6s?
Displacement (m)
4
3
2
1
0
1
2
3
Figure 7
135
4
5
6
Time (s)
Activity 2
My home to school roadmap
Objective
In this activity you should be able to make a roadmap that shows how you get
to school from your house.
Procedure
1.
2.
3.
Devise a way to easily measure distance. Let your teacher check your nonstandard measurement for precision.
Using your measuring device, gather the data that you will need for your
roadmap. Make sure that you take down notes of all names of the roads,
landmarks, corners, posts, and establishments you pass by. Record your data
properly.
Using your gathered data, draw your house-school roadmap on a short bond
paper. Decide on the most convenient scale to use when you draw your
roadmap. An example is shown below.
1 cm
Scale: 1 cm = 1 km
5 km
2 km
3 km
Figure 8
4.
Label your roadmap properly, including names of the roads, establishments,
etc. Specify also the length of road.
5.
Finally, let your teacher check again your work.
Q1. What is the total length of your travel from your house to your school?
Q2. What is the total displacement of your travel?
How fast?
After determining how far the object moves, the next question will be “How
fast did the object move?” This information can be provided by the object’s speed or
velocity.
Are you familiar with the traffic signs below? These signs tell us the maximum
or minimum speed limits allowed by law for road vehicles. In general, the minimum
speed limit in the Philippines is 60 km/h and the maximum speed limit is 100 km/h.
What are the units used in the above examples of speed limits? What
quantities do these units represent that are related to speed?
136
Activity 3
Fun walk
Objective
In this activity you should be able to gather data to determine who walks
fastest.
Procedure
1. Start by choosing a spacious place to walk straight.
2. Half of the group will walk while the other half will observe and record data.
3. Mark on the ground the starting line. All participants must start from the starting
line at the same time.
Upon receiving the go signal, all participants must start to walk as fast as they
could. The other members should observe closely as the participants walk and
determine who walks fastest.
5. Repeat #4 but this time, collect data to support your conclusion. Discuss within
your group how you are going to do this.
Q1. What quantities did you measure for your data?
Q2. How did you combine these quantities to determine how fast each participant
was walking?
Q3. How did you use the result to determine who walked fastest?
4.
Speed
The questions in the above activity are actually referring to speed. If you
know the speed of each participant, you can tell who is the fastest. Speed is defined
as distance travelled divided by the time of travel.
speed 
distance travelled
time of travel
The units of speed can be miles per hour (mi/h), kilometres per hour (km/h), or
meters per second (m/s).
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Q4. At constant distance, how is speed related to the time of travel?
Q5. At constant time to travel, how is speed related to the distance travelled?
Q6. Who was travelling faster than the other, a person who covered 10 meters in
5 seconds or the one who took 10 seconds to cover 20 meters?
Speed and direction
In describing the motion of an object, we do not just describe how fast the
object moves. We also consider the direction to where it is going. Speed with
direction is referred to as velocity. The sample weather bulletin below will show you
the importance of knowing not just the speed of the storm but also its direction.
Table 2: Sample weather bulletin
Weather Bulletin: Tropical Storm "Juaning"
Wednesday, 27 July 2011 at 09:27:14 AM
Location of
90 km East of Infanta,
Center
Quezon
Coordinates
14.8°N, 122.5°E
Strength of the
winds
Movement
Max. wind speed of 85 km/hr near the center & gustiness of up
to 100 km/hr
Forecast
On Wednesday AM: Expected to make landfall over Polillo
Island between 8am to 10am and over Southern Aurora by 1pm
to 3pm and will traverse Central Luzon
11km/hr going West-Northwest
Whenever there is a storm coming, we are notified of its impending danger in
terms of its speed and direction. Aside from this, we are also informed about its
strength. Do you know that as the storm moves, its winds move in circles? The
circular speed of the winds of the storm determines its strength. Different storm
signals are given in places depending on the circular speed of the winds of the storm
and the distance from the center.
Study again the weather bulletin above. Which is the speed for the circular
motion of the typhoon winds? Which is the speed for the motion of the storm as a
whole along the path? How important are speed and direction in determining the
weather forecast for the next hours?
Constant speed vs instantaneous speed
If you solved for the distance travelled by each participant over the time he
took to cover such distance, then you have computed for his average speed. But why
average speed and not just speed? It is considered average speed because it
represents the speed of the participant throughout his travel. During his travel, there
were instants that his speed would vary. His speed at an instant is called
instantaneous speed. Similarly, the velocity of a moving body at an instant is called
138
instantaneous velocity. The instantaneous speed may be equal, greater than, or less
than the average speed.
When an object’s instantaneous speed values are always the same, then it
means that the object is moving with constant speed. We refer to this as constant
motion. Where you will be and what time you will reach your destination is easily
predicted when you move at constant speed or velocity.
Are you familiar with the speedometer? Speedometer is a device used to
measure the instantaneous speed of a vehicle. Speedometers are important to the
drivers because they need to know how fast they are going so they know if they are
already driving beyond the speed limit or not.
How fast is the velocity changing?
Source: http://drrm.region4a.dost.gov.ph/
Figure 9. Track of tropical storm “Juaning”
In reality, objects do not always move at constant velocity. Storms like
“Juaning” also do change their speeds, directions, or both. The next activity will help
you analyze examples of motion with changing velocities (or with changing speed,
since we are only trying to analyze examples of motion in only one direction) using
tape charts and motion graphs.
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Activity 4
Doing detective work
Consider this situation below:
Supposed you were having your on-the-job training in a private investigating
company. You were asked to join a team assigned to investigate a ‘hit and
run’ case. The alleged suspect was captured by the CCTV camera driving
down a road leading to the place of incident. The suspect denied the
allegation, saying that he was then driving very slowly with a constant speed.
Because of the short time difference when he was caught by the camera and
when the accident happened, he insisted that it was impossible that he would
already be at the place when the crime happened. But when you were
viewing the scene again on the camera, you noticed that his car was leaving
oil spots on the road. When you checked these spots on site, you found out
that they are still evident. So you began to wonder if the spots can be used to
investigate the motion of the car of the suspect and check whether he was
telling the truth or not.
Here is an activity that you can do to help you with your investigation. You will
analyze the motion using strips of papers with dots. For this activity, assume that the
dots represent the ‘oil drops’ left by the car down the road.
Materials



ruler
paper strips with dots
cutter or pair of scissors
Procedure
A. Using tape chart
1.
2.
Obtain from your teacher paper strips with dots.
Label each dot. Start from 0, then 1, 2, 3, and so on. In this example, each dot
occurred every 1 second.
1 sec
0
1
2
3
Figure 10
3.
Examine the distances between successive dots.
140
Q1. How will you compare the distances between successive dots?
4.
Cut the strip at each drop, starting from
the first to the last drop, and paste them
side by side on a graph paper to form a
tape chart as shown in Figure 11.
4
3
Q2. How do the
compare?
lengths of
the
tapes
2
Q3. If each tape represents the distance
travelled by the object for 1 second, then
what ‘quantity’ does each piece of tape
provide?
1
Figure 11. Sample tape chart
Q4. What does the chart tell you about the speed of the car?
The difference in length between two successive tapes provides the object’s
acceleration or its change in speed or velocity for a time interval of 1 second.
Q5. How will you compare the changes in the lengths of two successive tapes?
Q6. What then can you say about the acceleration of the moving car?
B. Using motion graphs
5.
Measure the distance travelled by the car after 1 second, 2 seconds, and so on
by measuring the distance between drops 0 and 1, 0 and 2, and so on. Enter
your measurements in Table 3 on the right.
Table 3
Time of travel (s)
Distance travelled (m)
1
2
3
4
5
6.
Plot the values in Table 3 as points on the graph in Figure 12 on the right.
Q7. How does your distance-time graph look like?
141
Distance (cm)
0
Time (sec)
Figure 12
Join the mid-points of the tops of
the tapes with a line. You have
now converted your tape chart to
a speed-time graph.
Q8. How does you graph look like?
How is this different from your
graph in Figure 12?
4
Speed (cm/s)
7.
3
2
1
Q9. How will you interpret this graph
in terms of the speed and
acceleration of the moving car?
1
2
3
4
Time (s)
Figure 13
Q10. If you found out in your
investigation that the arrangement of oil drops left by the car is similar to what
you used in this activity, was the suspect telling the truth when he said that he
was driving with constant speed?
In this module, you have learned how to describe the motion of objects in
terms of position, distance and displacement, speed and velocity, and acceleration.
You have also learned how to represent motion of objects using diagrams, charts,
and graphs.
Let us summarize what you have learned by relating distance, displacement,
speed, velocity, and acceleration.

If an object does not change its position at a given time interval, then it is
at rest or its speed is zero or not accelerating.
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
If an object covers equal distance at equal intervals of time, then it is
moving at constant speed and still not accelerating.

If an object covers varying distances at equal intervals of time, then it is
moving with changing speed or velocity. It means that the object is
accelerating.
Links and References
Chapter 2: Representing Motion. Retrieved March 14, 2012 from http://igcse-physics-41-p2-yrh.brentsvillehs.schools.pwcs.edu/modules
Chapter 3: Accelerated Motion. Retrieved March 14, 2012 from http://igcse-physics-41-p2-yrh.brentsvillehs.schools.pwcs.edu/modules
HS Science IV: Physics in your environment. Teacher’s Edition. 1981. Science
Education Center. Quezon City
143
Suggested time allotment: 4 to 5
hours
Unit 3
MODULE
2
WAVES AROUND YOU
Waves occur all around you in the physical world. When you throw a stone
into a lake, water waves spread out from the splash. When you strum the strings of a
guitar, sound waves carry the noise all around you. When you switch on a lamp, light
waves flood the room. Water, sound, and light waves differ in important ways but
they all share the basic properties of wave motion. For instance, you can see water
waves and surfers would say that they enjoy riding the waves. On the other hand,
you don’t see sound waves and light waves but you experience them in other ways.
Your ears can detect sound waves and your skin can get burned by ultraviolet waves
if you stay under the sun for too long.
A wave is a periodic disturbance that moves away from a source and carries
energy with it. For example, earthquake waves show us that the amount of energy
carried by a wave can do work on objects by exerting forces that move objects from
their original positions. Have you personally experience an earthquake? How did it
feel? Did you know that you can understand earthquakes by studying waves?
In this module, you would be doing three activities that would demonstrate
the properties of wave motion. After performing these activities, you should be able
to:
1. explain how waves carry energy f rom one place to
another;
2. distinguish between transverse and longitudinal
waves;
3. distinguish between mechanical a nd
electromagnetic waves; and
4. create a model to demonstrate the relationship
among f requency, amplitude, wavelength, and
wave velocity.
144
Warm up. What are Waves?
Activity 1 will introduce you to different types of waves distinguished
according to the direction of vibrations of p articles with respect to the direction in
which the waves travel. Activity 2 will give you a background of the terms and
quantities used in describing periodic waves. Finally, Activity 3 will strengthen your
understanding of the properties of waves and how they propagate.
Try to wave at your seatmate and observe the
motion of your hand. Do you make a side-to-side motion
with the palm of your hand? Do you do an up-and-down
motion with your hand?
1.
Describe your personal hand wave.
The repetitive motion that you do with your hand
while waving is called a vibration. A vibration causes wave
motion. When you observe a wave, the source is always a
vibration.
2.
Think of a still lake. How would you generate water
waves on the lake?
Waving is a common
gesture that people do
to catch someone’s
attention or to convey a
farewell.
Activity 1. Let’s Make Waves!
What happens when waves pass by?
Objective
In this activity, you will observe and draw different types of waves and
describe how they are produced. You will also describe the different types of waves.
Time Allotment: 30 minutes
Materials





A rope (at least five meters long)
A colored ribbon
A coil spring (Slinky™)
A basin filled with water
A paper boat
145
Procedure
A.
What are transverse waves?
1.
Straighten the rope and place it above a long table. Hold one end of the
rope and vibrate it up and down. You would be able to observe a pulse.
Draw three sketches of the rope showing the motion of the pulse at three
subsequent instances (snapshots at three different times). Draw an arrow
to represent the direction of the pulse’s motion.
Time 1
Time 2
Time 3
a.
What is the source of the wave pulse?
b.
Describe the motion of your hand as you create the pulse.
c.
Describe the motion of the pulse with respect to the source.
You will now tag a specific part of the rope while making a series of
pulses. A periodic wave can be regarded as a series of pulses. One
pulse follows another in regular succession.
Figure 1. Periodic wave
146
Tie one end of the rope on a rigid and fixed object (e.g heavy table, door
knob, etc).
Figure 2. Rope tied to a rigid object
Attach a colored ribbon on one part of the rope. You may use adhesive
tape to fix the ribbon. Make a wave by continuously vibrating the end of
the rope with quick up-and-down movements of your hand. Draw the
waveform or the shape of the wave that you have created.
Ask a friend to vibrate the rope while you observe the motion of the
colored ribbon. Remember that the colored ribbon serves as a marker of
a chosen segment of the rope.
B.
a.
Does the wave transport the colored ribbon from its original position
to the end of the rope?
b.
Describe the vibration of the colored ribbon. How does it move as
waves pass by? Does it move in the same direction as the wave?
What are longitudinal waves?
1.
Connect one end of a long table to a wall. Place coil spring on top of
table. Attach one end of the coil spring to the wall while you hold the other
end.
147
Figure 3. Coil spring on a flat table
with one end attached to a wall
Do not lift the coil spring. Ask a friend to vibrate the end of the coil spring
by doing a back-and-forth motion parallel to the length of the spring.
Observe the waves along the coil spring. Draw how the coil spring looks
like as you move it back-and-forth.
2.
Attach a colored ribbon on one part of the coil spring. You may use an
adhesive tape to fix the ribbon. Ask a friend to vibrate the coil spring
back-and-forth while you observe the motion of the colored ribbon.
Remember that the colored ribbon serves as a marker of a chosen
segment of the coil spring.
a. Does the wave transport the colored ribbon from its original position to
the end of the rope?
b. Describe the vibration of the colored ribbon. How does it move as
waves pass by?
C.
What are surface waves?
1.
Place a basin filled with water on top of a level table. Wait until the water
becomes still or motionless. Create a wave pulse by tapping the surface
of the water with your index finger and observe the direction of travel of
the wave pulse. Tap the surface of the water at regular intervals to create
periodic waves. View the waves from above and draw the pattern that you
see. In your drawing, mark the source of the disturbance.
148
2.
Wait for the water to become still before you place your paper boat on the
surface. Create periodic waves and observe what happens to your paper
boat.
a. Do the waves set the paper boat into motion? What is required to set
an object into motion?
b. If you exert more energy in creating periodic waves by tapping the
surface with greater strength, how does this affect the movement of
the paper boat?
3.
If you were somehow able to mark individual water molecules (you used a
colored ribbon to do this earlier) and follow them as waves pass by, you
would find that their paths are like those shown in the figure below.
Water molecules move
in circular orbits when
waves passes by
Figure 4. Surface waves
a. As shown in the figure, the passage of a wave across a surface of a
body of water involves the motion of particles following a
___________ pattern about their original positions.
b. Does the wave transport water molecules from the source of the
vibration? Support your answer using the shown figure.
D.
Summary
1.
Waves can be typified according to the direction of motion of the vibrating
particles with respect to the direction in which the waves travel.
a. Waves in a rope are called ____________ waves because the
individual segments of the rope vibrate ____________ to the direction
in which the waves travel.
b. When each portion of a coil spring is alternatively compressed and
extended, ____________ waves are produced.
c. Waves on the surface of a body of water are a combination of
transverse and longitudinal waves. Each water molecule moves in a
_______________ pattern as the waves pass by.
149
2.
How do we know that waves carry energy?
3.
What happens when waves pass by?
Activity 2. Anatomy of a Wave
How do you describe waves?
Background
You had the experience of creating periodic waves in Activity 1. In a periodic
wave, one pulse follows another in regular succession; a certain waveform – the
shape of individual waves – is repeated at regular intervals.
Most periodic waves have sinusoidal waveforms as shown below. The
highest point and lowest point of a wave are called the crest and the trough
respectively. The amplitude is the maximum displacement of a vibrating particle on
either side of its normal position when the wave passes.
Figure 5. Sinusoidal wave
Objective
In this activity, you will identify the quantities used in describing periodic
waves.
Time Allotment: 40 minutes
Materials





A ruler
A basin filled with water
A rope (at least five meters long)
A colored ribbon
A watch or digital timer
150
Procedure
A.
How can you measure the wavelength of a wave?
1.
The wavelength of a wave refers to the distance between any
successive identical parts of the wave. For instance, the distance from
one crest to the next is equal to one full wavelength. In the following
illustration, this is given by the interval B to F. Identify the other intervals
that represent one full wavelength.
__________________________________________________________
__________________________________________________________
2.
Place a basin filled with water on top of a level table. Wait for the water to
become still. Create a vibration by regularly tapping the surface of the
water with your index finger. You would be able to see the subsequent
crest of the water waves.
Figure 6. Crest and trough on a water wave
Draw the water waves as you see them from the top of the basin. Label
one wavelength in your drawing.
151
3.
Increase the rate of the vibrations you create by tapping the surface of the
water rapidly. What happens to the wavelength of the waves?
Draw the water waves as you see them from the top of the basin.
Compare it with your drawing in number 2.
B.
How do you measure the frequency of a wave?
1.
The frequency of a series of periodic waves is the number of waves that
pass a particular point every one second. Just like what you have done in
Activity 1, attach a colored ribbon on a rope to serve as a tag. Tie one
end of the rope on a fixed object and ask a friend to create periodic
waves by regularly vibrating the other end of the rope.
2.
You will count how many times the colored ribbon reached the crest in 10
seconds. You will start counting once the ribbon reaches the crest a
second time. It means that one wave has passed by the ribbon’s position.
Ask another friend with a watch or a digital timer to alert you to start
counting and to stop counting after 10 seconds. Record the results in
Table 1.
3.
It is also useful to consider the period of a wave, which is the time
required for one complete wave to pass a given point. The period of each
wave is
From the identified frequency of the observed periodic waves, the period
can be calculated. For example, if two waves per second are passing by,
each wave has a period of ½ seconds.
Table 1. Frequency and period of the wave
Number of waves
Frequency
(N cycles) that passed
of the waves
by the ribbon in 10
(N cycles/10 seconds)
seconds
Period
of the waves (seconds)
The unit of frequency is the hertz (Hz); 1 Hz = 1 cycle/second.
152
4.
C.
If you increase the frequency of vibration by jerking the end of the rope at
a faster rate, what happens to the wavelength?
How do you measure the speed of a wave?
1.
Using the rope with ribbon. Create periodic waves and estimate their
wavelength. Count the number of waves that pass by the ribbon in ten
seconds. Compute the frequency of the waves. Record the results in
Table 2.
2.
The wave speed is the distance traveled by the wave per second.
wave speed = distance traveled per second = frequency x wavelength
From the basic formula that applies to all periodic waves, you can see
that wave speed, frequency and wavelength are independent of the
wave’s amplitude.
a. Using the data from number 1, calculate the wave speed of the
observed periodic waves. Record the result in Table 2.
Table 2. The speed of a wave
Number of
waves
Estimated
(N cycles) that
wavelength
passed by the
(meters)
ribbon in 10
seconds
Frequency
of the waves
(N cycles/10
seconds)
Wave speed
(meter/second)
Summary
1.
What is the relationship between wave speed, wavelength and
frequency?
2.
Suppose you observed an anchored boat to rise and fall once every 4.0
seconds as waves whose crests are 25 meters apart pass by it.
a. What is the frequency of the observed waves?
b. What is the speed of the waves?
153
Activity 3. Mechanical vs. Electromagnetic Waves
How do waves propagate?
Objective
In this activity, you will differentiate between mechanical waves and
electromagnetic waves.
Time Allotment: 30 minutes
Materials


A.
Findings from Activity 1
Chart of the electromagnetic spectrum
What are mechanical waves?
1.
When you created waves using a rope in Activity 1 Part A, you were able
to observe a moving pattern. In this case, the medium of wave
propagation is the rope.
a. In Activity 1 Part B, what is the medium of wave propagation?
b. In Activity 1 Part C, what is the medium of wave propagation?
2.
The waves that you have created
in Activity 1 all require a medium
for wave propagation. They are
called mechanical waves.
a. How can you generate
mechanical waves?
3.
The medium of propagation for the wave
shown above is the rope.
All three kinds of waves – transverse, longitudinal, and surface – are sent
out by an earthquake and can be detected many thousands of kilometers
away if the quake is a major one.
a. What do you think is the source of earthquake waves?
b. What is the medium of propagation of earthquake waves?
154
B.
What are electromagnetic waves?
1.
Energy from the sun reaches the earth through electromagnetic waves.
As opposed to mechanical waves, electromagnetic waves require no
material medium for their passage. Thus, they can pass through empty
space. Locate the electromagnetic spectrum chart in your classroom. A
smaller image of the chart is shown below. Identify the common name of
each wave shown in the chart.
1. _____________________
5. _____________________
2. _____________________
6. _____________________
3. _____________________
7. _____________________
4. _____________________
2.
The electromagnetic spectrum shows the various types of
electromagnetic waves, the range of their frequencies and wavelength.
The wave speed of all electromagnetic waves is the same and equal to
the speed of light which is approximately equal to 300 000 000 m/s.
Figure 7. The electromagnetic spectrum
a.
Examine the electromagnetic spectrum.
1.
Describe the relationship between frequency
wavelength of each electromagnetic wave.
155
and
2.
Draw waves to represent each electromagnetic wave. Your
illustrations must represent the wavelength of a wave
relative to the others. For instance, gamma rays have a very
small wavelength compared to the other waves in the
spectrum.
1. Gamma Rays
2. __________
3. __________
4. __________
5. __________
6. __________
7. __________
b.
The Sun is an important source of ultraviolet (UV) waves, which is
the main cause of sunburn. Sunscreen lotions are transparent to
visible light but absorb most UV light. The higher a sunscreen’s
solar protection factor (SPF), the greater the percentage of UV
light absorbed. Why are UV rays harmful to the skin compared to
visible light?
Compare the frequency and energy carried by UV waves to that of
visible light.
156
C.
Summary
1.
Mechanical waves like sound, water waves, earthquake waves, and
waves in a stretched string propagate through a _______________ while
__________________ waves such as radio waves, visible light, and
gamma rays, do not require a material medium for their passage.
Review. Waves Around You
The activities that you have performed are all about wave motion or the
propagation of a pattern caused by a vibration. Waves transport energy from one
place to another thus they can set objects into motion.
What happens when waves pass by?
Activity 1 introduced you to transverse waves, longitudinal waves, and
surface waves. You observed the motion of a segment of the material through which
the wave travels.
1.
Transverse waves occur when the individual particles or segments of a
medium vibrate from side to side perpendicular to the direction in which
the waves travel.
2.
Longitudinal waves occur when the individual particles of a medium
vibrate back and forth in the direction in which the waves travel.
3.
The motion of water molecules on the surface of deep water in which a
wave is propagating is a combination of transverse and longitudinal
displacements, with the result that molecules at the surface move in
nearly circular paths. Each molecule is displaced both horizontally and
vertically from its normal position.
4.
While energy is transported by virtue of the moving pattern, it is
important to remember that there is not net transport of matter in wave
motion. The particles vibrate about a normal position and do not
undergo a net motion.
157
How can you describe waves?
In Activity 2, you have encountered the important terms and quantities used
to describe periodic waves.
1.
The crest and trough refer to the highest point and lowest point of a
wave pattern, respectively.
2.
The amplitude of a wave is the maximum displacement of a particle of
the medium on either side of its normal position when the wave passes.
3.
The frequency of periodic waves is the number of waves that pass a
particular point for every one second while the wavelength is the
distance between adjacent crests or troughs.
4.
The period is the time required for one complete wave to pass a
particular point.
5.
The speed of the wave refers to the distance the wave travels per unit
time. It is related to the frequency of the wave and wavelength through
the following equation:
wave speed = frequency x wavelength
How do waves propagate?
Finally, Activity 3 prompted you to distinguish between mechanical and
electromagnetic waves.
1.
In mechanical waves, some physical medium is being disturbed for the
wave to propagate. A wave traveling on a string would not exist without
the string. Sound waves could not travel through air if there were no air
molecules. With mechanical waves, what we interpret as a wave
corresponds to the propagation of a disturbance through a medium.
2.
On the other hand, electromagnetic waves do not require a medium to
propagate; some examples of electromagnetic waves are visible light,
radio waves, television signals, and x-rays.
158
References and Web Links
Anatomy of an electromagnetic wave. Available at:
http://missionscience.nasa.gov/ems/02_anatomy.html
Electromagnetic waves. Available at:
http://www.colorado.edu/physics/2000/waves_particles/
[3] Hewitt, P. (2006). Conceptual Physics 10 th Ed. USA: Pearson Addison-Wesley.
The anatomy of a wave. Available at:
http://www.physicsclassroom.com/class/waves/u10l2a.cfm
The nature of a wave. Available at:
http://www.physicsclassroom.com/class/waves/u10l1c.cfm
159
Suggested time allotment: 8 to 10 hours
Unit 3
MODULE
3
SOUND
Would you like to try placing your palm on your throat while saying – “What
you doin?” What did your palm feel? Were there vibrations in the throat? Try it again
and this time, say – “Mom! Phineas and Ferb are making a title sequence!”
In the previous module you learned
about wave properties and common
characteristics like pitch and loudness. You
will also learn the 2 kinds of waves according
to propagation. These are the longitudinal and
transverse waves. Sound is an example of a
longitudinal wave. It is also classified as a
mechanical wave. Thus there has to be matter
for which sound should travel and propagate.
This matter is better known as medium.
Terms to Remember
Longitudinal Wave
- Wave whose motion is parallel
to the motion of the particles of
the medium
Mechanical wave
- Wave that need a medium in
order to propagate
Figure 1. Longitudinal wave
How does sound propagate?
In Activity 1, you will try to explore how sound is produced. You are going to
use local materials available in your community to do this activity. You can do “Art
Attack” and be very creative with your project.
160
Activity 1
My own sounding box
Objectives
In this activity, you should be able to construct a sounding box to
1.
demonstrate how sound is produced; and
2.
identify factors that affect the pitch and loudness of the sound produced.
Materials Needed





shoe box
variety of elastic or rubber bands (thin and thick)
extra cardboard – optional
pair of scissors or cutter
ruler
TAKE
CARE!
Handle all sharp
tools with care.
Procedure
1.
Cut and design your shoe box as shown in Figure 2.
2.
Put the rubber bands around the
box. Make sure that the rubber
bands are almost equally spaced
and that the rubber bands are
arranged according to increasing
thickness from the lower end to
the other end of the box.
3.
Use your finger to pluck each
rubber band. Listen to the sound
produced.
Figure 2. My sounding box
Q1.
What physical signs did you observe when you plucked each band. Did
you hear any sound? What produced the sound?
161
Q2.
4.
This time use the fingers of one hand to stretch one of the elastics. Pluck the
elastic with the fingers of the other hand and observe.
Q3.
5.
How different are the sounds produced by each band with different
thickness?
Are there changes in the note when you plucked the stretched band?
Repeat step 4 with the other elastic bands.
Q4.
Arrange the elastics in sequence from the highest note to the lowest
note produced.
When we talk or make any sound, our vocal cords vibrate. When there are no
vibrations felt, no sound is produced. This means that sounds are caused by
vibrations. Vibrations of molecules are to the to-and-fro or back-and-forth movement
of molecules. Vibrations are considered as a disturbance that travels through a
medium. This vibratory motion causes energy to transfer to our ears and is
interpreted by our brain. Sound waves are examples of longitudinal waves. They
are also known as mechanical waves since sound waves need medium in order to
propagate.
In Activity 1, vibrations produced by the elastic band produced sound.
sounding box amplified (increase in amplitude) this sound.
The
Sound waves can travel in air. When they come in contact with our
eardrums, the vibrations of the air force our eardrums to vibrate which is sensed and
interpreted by our brain.
Can sound waves also travel in other media like
solids and liquids?
You can try this one. Place your ear against one end of a tabletop. Ask a
friend to gently tap the other end of the table with a pencil or a ruler. What happens?
Then ask your friend to again gently tap the other end of the table but this time, make
sure that your ear is not touching the table. What happens? In which situation did
you encounter louder and more pronounced sound? In which situation did you
encounter the sound clearly?
Sound is produced by the slight tapping of the table with a pencil or a ruler.
This can be heard clearly at the other end of the table. This shows that sound waves
can also travel through wood or solid. Sound is more distinct in solids than in air.
This also means that sound is heard much louder when it travels in solids than in air.
162
What about in liquids? Can
sound travel in liquids too? Liquids
are better transmitters of sound
than gases. If two bodies are struck
together underwater, the sound
heard by a person who is
underwater is louder than when
heard in air, but softer than in
solids.
Figure 3: Molecules of different media
As you can see in Figure 3, particles of solids are more closely packed than
particles of liquid and gas. This is why sound produced in solids is much more
distinct and loud than when it is propagated or produced in liquids and gas. Between
liquids and gases, on the other hand, liquid particles appear more closely spaced
than gases. This means that louder sound will be produced in liquids than in gases.
Spacing of particles of the medium like solid, liquid and gas is an important
factor on how would is transmitted. Take a look at Figure 3, liquid particles are
closer to each other than the particles in the gas. Sound waves are transmitted
easier in liquids. Between liquids and solids, the particles of solids are even closer
together than the liquid molecules; therefore, sound travels even faster in solids than
in liquids. Since different media transmit sound differently, sound travels at different
speeds in different materials. Since solid is the best transmitter of sound, sound
travels fastest in solids and slowest in gases.
The table below shows the speed of sound in different materials.
Table 1: Speed of sound in different materials
Materials
Speed of Sound
V (m/s)
Air (0oC)
He (0oC)
H (20oC)
Water
Seawater
Iron and Steel
Aluminum
Hard wood
331
1005
1300
1440
1560
5000
5100
4000
Sound speed is dependent on several factors such as (1) atmospheric
pressure, (2) relative humidity, and (3) atmospheric temperature. Remember these
weather elements you studied in your earlier grades? High values of these elements
lead to faster moving sound. When you are in the low lands and the surrounding is
hot, sound travels fast. Do you want to know why sound travels faster in hot air?
There are more molecular interactions that happen in hot air. This is because the hot
particles of air gain more kinetic energy and so there is also an increase in the mean
velocity of the molecules. Since sound is a consequence of energy transfer through
collisions, more collisions and faster collisions means faster sound.
163
Going a little deeper on this, speed of sound basically depends on the elastic
property and the inertial property of the medium on which it propagates. The elastic
property is concerned with the ability of the material to retain or maintain its shape
and not to deform when a force is applied on it. Solids as compared to liquids and
gases have the highest elastic property. Consequently, solid is the medium on which
sound travels fastest. This means that the greater the elastic property, the faster the
sound waves travel. The inertial property, on the other hand, is the tendency of the
material to maintain its state of motion. More inertial property means the more inert
(more massive or greater mass density) the individual particles of the medium, the
less responsive they will be to the interactions between neighboring particles and the
slower that the wave will be. Within a single phase medium, like air for example,
humid air is more inert than humid air. This is because water that has changed to
vapor is mixed with the air. This phenomenon increases the mass density of air and
so increases the inertial property of the medium. This will eventually decrease the
speed of sound on that medium.
Sound cannot travel in a vacuum. Remember that sound is a mechanical
wave which needs medium in order to propagate. If no matter exists, there will be no
sound. In the outer space, sound would not be transmitted.
Sound waves possess characteristics common to all types of waves. These
are frequency, wavelength, amplitude, speed or velocity, period and phase. Just like
other waves, sound also exhibits wave properties just like reflection, refraction,
diffraction, and interference. More than these properties are pitch and loudness of
sound. Pitch refers to the highness or lowness of sound. Loudness is how soft or
how intense the sound is as perceived by the ear and interpreted by the brain. Do
you want to find out more characteristics and properties of sound? Activity No. 2 will
let your discover some of these properties using your sounding box.
Activity 2
Properties and characteristics of sound
Objective
In this activity, you will use your sounding box to describe the characteristics
of sound and compare them with those of sound produced by a guitar.
Materials Needed




Sounding Box
Wooden rod
Ruler
Guitar
164
Procedure
Part 1: Sounding the Box...
1.
Label the rubber bands of your sounding box as S1, S2 and so on. Labeling
should start with the thinnest rubber band.
2.
Pluck each rubber band. Listen to the sounds produced.
Q1. What did you observed when you plucked each of the rubber bands and sound
is produced? How then is sound produced?
Q2. Is there a difference in the sound produced by each of the rubber bands? How
do they differ?
Q3. Which band produced a higher sound? Which band produced a lower sound?
Q4. How can you make a softer sound? How can you make a louder sound?
Q5. What factors affect the pitch and loudness of the sound produced by the rubber
bands?
3.
Stretch one of the rubber bands and while doing so, pluck it again.
Q6. Is there a change in the sound produced when you pluck the rubber band while
stretching it? How does stretching the rubber band affect the pitch of the sound
produced?
4.
Place a ruler (on its edge) across the
sounding box as shown in Figure 4.
Pluck each rubber band and observe.
ruler
ruler
Q7. Is there a difference in the sound
produced when the ruler is placed
across the box?
Figure 4: With stretch rubber
bands
5.
Move the ruler off center to the left or to a
diagonal position so that one side of each
rubber band is shorter than the other side
(Figure 5). Pluck again each rubber band on
each side of the ruler and observe.
Figure 5: Diagonal
stretching of the bands
165
Q8. Which part of the rubber band (shorter side or longer side) provides higher
pitch? Which part provides lower pitch?
Q9. Again, what factors affect the pitch of the sound produced by the rubber
bands?
Part 2: The Guitar...
6.
Strum each guitar string without holding the frets. (String #0 is the lower most
string while string #6 is the uppermost string.)
7.
Record all you observations in the table provided.
String #
0
1
2
3
4
5
6
Pitch (High or Low)
Q10.
Which string vibrates fastest when strummed?
Q11.
Which string vibrates slowest when strummed?
Q12.
Which string has the highest frequency?
Q13.
Which string has the highest pitch?
Q14.
Which has the lowest frequency?
Q15.
Which string has the lowest pitch?
Q16.
How would you relate pitch and frequency?
The highness or lowness of sound is known as the pitch of a sound or a
musical note. In Activity 2, you were able to relate vibrations, frequency and pitch
using your improvised sounding box and a guitar. The pitch of a high frequency
sound is also high and a low frequency sound is also; lower in pitch.
166
When you were in your earlier
grades you studied about the human
ear. Our ear and that of animals are the
very sensitive sound detectors. The ear
is a part of the peripheral auditory
system. It is divided into three major
parts: the outer ear, the middle ear and
the inner ear.
The outer ear called the pinna
collects the sound waves and focuses
them into the ear canal. This canal
transmits the sound waves to the
eardrum.
Figure 6 The human ear
The ear canal is the eardrum membrane or the tympanum. It separates the
outer and the middle ears physically. Air vibrations set the eardrum membrane in
motion that causes the three smallest bones (hammer, anvil and stirrup) to move.
These three bones convert the small-amplitude vibration of the eardrum into largeamplitude oscillations. These oscillations are transferred to the inner ear through the
oval window.
Behind the oval window is a snail-shell shaped liquid –filled organ called the
cochlea. The large-amplitude oscillations create waves that travel in liquid. These
sounds are converted into electrical impulses, which are sent to the brain by the
auditory nerve. The brain, interprets these signals as words, music or noise.
Did you know that we can only sense within the frequency range of about 20
Hz to about 20000 Hz? Vibrational frequencies beyond 20 000 Hz is called
ultrasonic frequencies while extremely low frequencies are known as infrasonic
frequencies. Our ear cannot detect ultrasonic or infrasonic waves. But some
animals like dogs can hear sounds as high as 50 000 Hz while bats can detect
sounds as high as 100 000 Hz.
We can see images of your baby brother or sister when the OB-Gyne asks
your mommy or nanay to undergo ultrasound. Ultrasonic waves are used to help
physicians see our internal organs. Nowadays, ultrasonic technology is of three
kinds: 2-dimensional, 3-dimensional, and 4-dimensional categories. In the 3- and 4dimensional ultrasonic technologies, the features of the fetus are very clearly
captured.
167
It has also been found that ultrasonic waves can be used as rodent and
insect exterminators. The very loud ultrasonic sources in a building will usually drive
the rodents away or disorient cockroaches causing them to die from the induced
erratic behavior. What other applications of sound do you have in mind? Do you want
to share them too?
Loudness and Intensity
Do you still remember intensity of
light in the previous module? In sound,
intensity refers to the amount of energy a
sound wave. Figure 7 shows varying
intensity of sound. High amplitude sounds
usually carry large energy and have higher
intensity while low amplitude sound carry
lesser amount of energy and have lower
intensity.
Figure 7: Varying sounds
Sound intensity is measured by various instruments like the oscilloscope.
Loudness is a psychological sensation that differs for different people. Loudness is
subjective but is still related to the intensity of sound. In fact, despite the subjective
variations, loudness varies nearly logarithmically with intensity. A logarithmic scale is
used to describe sound intensity, which roughly corresponds to loudness. The unit of
intensity level for sound is the decibel (dB), which was named after Alexander
Graham Bell who invented the telephone. On the decibel scale, an increase of 1 dB
means that sound intensity is increased by a factor of 10.
Father and son duo interprets the loudness of a sound differently. The son
considers the rock music a soft music while the father considers it a loud sound. The
father may even interpret the sound as a distorted sound, which is known as noise.
Noise is wave that is not pleasing to the senses.
168
Table 2. Sound Levels of different sound sources
Source of sound
Jet engine, 30 m away
Threshold of pain
Amplified rock music
Old subway train
Average factory
Busy street traffic
Normal conversation
Library
Close whisper
Normal breathing
Threshold of hearing
Level (dB)
140
120
115
100
90
70
60
40
20
10
0
Let’s see how you interpret sound yourselves. Look for 3 more classmates
and try Activity 3. This will test your ability to design and at the same time show your
talents!
Activity 3
Big time gig!
Objectives
In this activity, you should be able to:
1.
create musical instruments using indigenous products and
2.
use these instruments to compose tunes and present in a Gig. Students
may also utilize other indigenous musical instruments.
Materials Needed



Indigenous materials such as sticks, bottles or glassware available in your
locality to be used as musical instrument
Localized or improvised stringed instruments
Localized or improvised drum set
Procedure
1.
2.
3.
4.
Form a group of four (4). One can play a stringed instrument, while the other
can play the drum and the 3rd member can use the other instrument that your
group will design or create. The last member will be your group’s solo
performer.
Look for local materials which you can use to create different musical
instruments.
Try to come up with your own composition using the instruments you have
created.
In the class GIG you are to play and sing at least 2 songs (any song of your
choice and your original composition).
169
5.
Check the Rubric included to become familiar with the criteria for which you will
be rated.
Big Time Gig!
Rubric Scoring
Task/
Criteria
Improvised/
Localized
musical
instruments
Composition
Performance
Cooperation
and Team
Work
4
3
2
1
 Makes use
of local or
indigenous
materials
 The
improvised
instruments
produce
good quality
sound
comparable
to standard
musical
instruments.
 Makes use
of local
materials
only.
 The
improvised
instruments
produce
good quality
sound.
 Makes use
of local
materials
only.
 The
improvised
instruments
produce fair
quality
sound.
 Makes use
of local
materials
only.
 The sound
produced by
the
improvised
instruments
is not clear
and distinct.
The group’s
original
composition
has good
melody.
The group’s
original
composition
has fair
melody and
the lyrics
provided are
thematic and
meaningful
The group’s
original
composition
has fair
melody and
the lyrics
provided are
NOT thematic
but
meaningful
The group’s
original
composition
has fair
melody and
the lyrics
provided are
NEITHER
thematic nor
meaningful
 The group
was able to
successfully
use the
improvised
musical
instruments
in their GIG.
 The group
was able to
provide fair
rendition.
 The group
was able to
use the
improvised
musical
instruments
but some
were out of
tune
 The group
was able to
provide fair
rendition.
 The group
was able to
use the
improvised
musical
instruments
but MOST
were out of
tune
 The group
was able to
provide fair
rendition
3 out of 4
members
completed
their task so
as to come up
with the
expected
output - GIG
2 out of 4
completed
their task so
as to come up
with the
expected
output - GIG
Only 1 out of
the 4
members did
his/her job
The lyrics
provided are
thematic and
meaningful
 The group
was able to
successfully
use the
improvised
musical
instruments
in their GIG.
 The group
was able to
provide
good quality
rendition or
performance
Each one of
them
completed
their task so
as to come up
with the
expected
output - GIG
TOTAL:
170
Score
How was your GIG? Did you enjoy this activity? Aside from the concepts and
principles in sound you learned and applied for a perfect performance what other
insights can you identify? Can you extend your designs to come up with quality
instruments using indigenous materials? You can be famous with your artworks...
Sound waves are mechanical waves than need for a medium for sound to
propagate. Vibrations of the medium create a series of compression and rarefaction
which results to longitudinal waves. Sound can travel in all media but not in vacuum.
Sound is fastest in matter that is closely packed like solid and slowest in gas. Speed
of sound is dependent on factors like temperature, humidity and air pressure. High
temperature brings much faster sound. Increased humidity, on the other hand makes
sound travel slower. As pressure is increased, speed is also increased. Inertial and
elastic properties of the medium also play an important part in the speed of sound.
Solids tend to be highly elastic than gases and thus sound travel fastest in solids. In
a single phase matter however, the inertial property which is the tendency of the
material to maintain its motion also affect speed of sound. Humid air is more massive
and is more inert than dry air. This condition brings lesser molecular interactions and
eventually slower sound. Sound, just like other waves do have characteristics such
as speed, frequency, wavelength, amplitude, phase and period. Like any other wave,
sound exhibit properties like reflection, refraction, interference and diffraction. Other
properties are loudness and pitch. Pitch is dependent on the frequency of sound
wave. The higher frequency the higher the pitch of the sound produced.
Organisms like us are capable of sensing sound through our ears. Just like
other organism, our ears do have parts that perform special tasks until the auditory
signals reach and are interpreted by our brain. Frequencies beyond the audible to
human are known as ultrasonic (beyond the upper limit) and infrasonic (below the
lower limit). Intensity and loudness are quantitative and qualitative descriptions of the
energy carried by the wave. High amplitude waves are intense and are sensed as
loud sound. Low amplitude sound waves are soft sound. Music is a special sound
that forms patterns and are appealing to our sense of hearing.
Up Next. Light
In the next module, you would learn about visible light, the most familiar form
of electromagnetic waves, since it is the part of the electromagnetic spectrum that
the human eye can detect. Through some interesting activities, you would come
across the characteristics of light, how it is produced and how it propagates. You
would need the concepts that you learned from this module to fully understand and
appreciate the occurrence of light.
Reading Materials/Links/Websites
http://www.physicsclassroom.com/Class/sound/u11l2c.cfm
http://en.wikipedia.org/wiki/Sound#Sound_wave_properties_and_characteristics
http://personal.cityu.edu.hk/~bsapplec/characte.htm
http://www.slideshare.net/agatonlydelle/physics-sounds
171
Suggested time allotment: 5 to 6 hours
Unit 3
MODULE
4
LIGHT
Do you still remember Sir Isaac Newton? What about Christian Huygens? Did
you meet them in your earlier grades? These people were the first to study about
light.
In this module, you will learn about light. You will also find out that there are
different sources of light and that light exhibits different characteristics and
properties. Finally, you will design a simple activity to test whether light travels in a
straight light or not.
What are the common sources of light?
How do these common sources produce light?
What are the common properties and characteristics of
light?
Sir Isaac Newton believed that light behaves like a particle while Christian
Huygens believed that light behaves like a wave. A 3 rd scientist, Max Planck came
up with what is now known as the Dual-Nature of Light. He explained that light can
be a particle and can also be a wave. To complete our knowledge about the nature
of light, James Clark Maxwell proposed the Electromagnetic Theory of Light.
While these scientists dig deep into the nature of light and how light are
propagated, let us be more familiar with ordinary materials we use as common
sources of light. The Sun for example is known as a natural source of light. Sun is
also considered as a luminous body (an object capable of producing its own light).
Other sources are the lamps, bulbs, and candles. These are the artificial sources.
In your earlier grades you learned about energy transformation. Energy
transformation is needed to convert or transform forms of energy to light or other
forms. In bulbs, electric potential is converted to light. In lamps, chemical energy is
transformed to light.
172
In Activity 1, you will try to observe transformation of chemical energy from
chemical substances such as oil to light. Further, you will also gather data which
chemical substance is best by relating it to the brightness of the light produced. In
this activity, you will use the langis kandila or lampara as we call it in the Philippines
or the Diwali lights as it is known in other countries like India.
Activity 1
Light sources: Langis kandila or lampara
Objectives
In this activity, you should be able to:
1. construct a simple photometer;
2. determine which chemical substance produce the brightest light; and
3. infer that brightness of light is dependent on the distance of the source.
Materials Needed








an electric glow lamp (Small lamp is needed)
candle - weighing 75 grams
wedge with sloping surfaces (sharp angle about 60° to 70 ° that serve as the
photometer (made of white wood or paper)
langis kandila or lampara
variety of vegetable oil (about 5)
aluminum pie containers or small clay pots
cotton string for wick
set of books or tripod that will serve as platform for Diwali lights
Procedure
Part 1: Improvised Photometer
Arrange the electric glow
lamp, the candle and the
wedge as shown on the
right. Make sure that you
do this activity in a dark
room for good results.
1
2
Figure 1. Improvised photometer set up
Illuminate the side “A” of the wedge by the lamp and side “B” by the candle.
In general the lamp side will look brighter than the other.
173
Move the wedge nearer to the candle to a spot at which you as an observer,
looking down on the two surfaces of the wedge (from “C”) cannot see any difference
between them in respect of brightness. (They are then equally illuminated; that is to
say the candle light falling on “B” is equal in intensity to the electric light falling on
“A.”)
Calculate the power of the lamp relative to the candle. (e.g. If both side of the
wedge showed equal illumination when it is about 200 cm from 1, and 50 cm from 2,
the distances are as 4 to 1. But as light falls off according to the square of the
distance: (200)2 = 40 000 and (50)2 = 2 500 or 16 to 1.). Thus the candle-power of
the lamp is 16.
Q1. What is the candle power of your set up? (Include your computations.)
Part 2: Langis Kandila or Lampara
1.
Make 5 langis kandila or lampara using
aluminium pie containers or small clay pots
as shown. Label your langis kandila as DLKL1, DL-KL2 and so on.
2.
Pour different variety of vegetable oil in each
of the pot.
3.
Use the improvised photometer to determine the brightness of each of the
candle.
4.
Replace the candle you used in the 1st part with the langis kandila.
5.
Compute the candle power of the lamp with respect to the langis kandila. You
may refer to step 4 for the step by step process of determining the candle
power using the improvised photometer. Record your data on the provided
table:
Figure 2. Langis kandila or
lampara
Table 1. Brightness of Vegetable Oil Variety
Diwali Lights/Langis
Vegetable Oil Variety
Kandila
DL-LK 1
Canola Oil
DL-LK 2
Butter
DL-LK 3
Margarine
DL-LK 4
Corn Oil
DL-LK 5
Olive Oil
Brightness/Luminous
Intensity (Candela)
Q2. Which among the langis kandila or lampara is the brightest?
174
Part 3: Intensity vs Distance from light source
1.
Position your brightest Diwali light or langis kandila 20 inches or about 50 cm
from the wedge. Compute the brightness of the Diwali light.
2.
Move the langis kandila or Diwali light 10 cm closer then compute the
brightness.
3.
Repeat step 2 and each time move the langis kandila or Diwali light 10 cm
closer to the wedge. Compute the corresponding brightness and record your
data on the table below.
Distance from the
Wedge (cm)
50
40
30
20
10
Observation
Brightness
(Candela)
Q3. How would you relate the brightness or intensity of light with the distance from
the source?
Brightness of light depends on the source and the distance from the source.
Brightness however, is qualitative and is dependent of the person’s perception.
Quantitatively, brightness can be expressed as luminous intensity with a unit known
as candela. The unit expression came from the fact that one candle can
approximately represent the amount of visible radiation emitted by a candle flame.
However, this decades-ago assumption is inaccurate. But we still used this concept
in Activity 1 as we are limited to an improvised photometer. If you are using a real
photometer on the other hand, luminous intensity refers to the amount of light power
emanating from a point source within a solid angle of one steradian.
Further, in Activity 1, varied chemical sources produced different light
intensity. Likewise, different distances from the light source provided varied
intensity.
As mentioned earlier, James Clark Maxwell discovered the Electromagnetic
Theory of Light. He combined the concepts of light, electricity and magnetism to
come up with his theory forming electromagnetic waves. Since these are waves they
also exhibit different characteristics of waves such as wavelength, frequency and
wave speed which you have studied in the previous module. There are different
forms of electromagnetic waves arranged according to frequency. This arrangement
of the electromagnetic waves is known as Electromagnetic spectrum. The visible part
of which is known as white light or visible light. The next activity will lead you to
explore the characteristics of the electromagnetic spectrum.
175
Activity 2
My spectrum wheel
Objectives
In this activity, you should be able to
1. construct a spectrum wheel and
2. explore the characteristics of light such as energy, frequency and
wavelength.
Materials Needed




Spectrum Wheel Pattern
Cardboard or illustration board
Button fastener
Glue or paste
TAKE
CARE!
Handle all sharp
Objects with
care.
Procedure
Part 1: Spectrum Wheel
1.
Cut the two art files that make up the wheel on the next pages.
2.
Cut along the lines drawn on the top wheel. The small window near the center
of the wheel should be completely cut out and removed.
3.
Punch a whole into the center of the two wheels together. You may use a
button fastener to hold the two wheels securely in place, one on top of the
other, but they should be free to rotate relative to each other.
4.
When you see a region of the EM spectrum show up in the open window and
the "W,F,E" that correspond to that region showing up under the flaps then you
know that you have done it right.
176
Source: Sonoma State University (http://www.swift.sonoma.eu)
177
178
Part 2: Characteristics of Light
Try out your Spectrum Wheel by positioning the inner most of the flaps on EM
SPECTRUM. This will simultaneously position the other flaps to ENERGY,
WAVELENGTH & FREQUENCY.
Turn the upper wheel and observe the combinations.
Fill in the table below with the corresponding combinations you have
observed using your Spectrum Wheel.
Table 2. Characteristics of Light
EM
Energy
Spectrum
Radio
Frequency
Wavelength
Frequency x
wavelength
Microwave
Infrared
Visible Light
Ultraviolet
X-Ray
Gamma Ray
Q1. How are frequency and wavelength related for a specific region of the
spectrum?
Q2. What can you observe with the values of the product of frequency and
wavelength in the different spectra?
Q3. How is ENERGY related to FREQUENCY?
Now that we are familiar with the electromagnetic spectrum and the
corresponding energies, frequencies and wavelength probably we can see some
applications of these in everyday living. UV rays are highly energetic than other
spectral regions on its left. This could be a possible reason why we are not advised
to stay under the sun after 9:00 in the morning. Prolong use of mobile phones may
cause ear infection. This may be due to a higher energy emitted by microwaves used
in cellular phones than radio waves commonly used in other communication devices.
What about the visible spectrum? Do you want to know more about this spectral
region?
179
What are the frequencies and energies of the
visible spectrum? This is the visible light. Sir Isaac
Newton used a prism to show that light which we
ordinarily see as white consists of different colors.
Dispersion is a phenomenon in which a prism
separates white light into its component colors.
Activity 3 will provide you more information about
visible light. In this activity, you will be able to detect
relationships between colors, energy, frequency,
wavelength and intensity.
Figure 3. Color spectrum
Activity 3
Colors of light – color of life!
Objectives
In this activity, you should be able to
1. make a color spectrum wheel;
2. explore the characteristics of color lights; and
3. observe how primary colors combine to form other colors.
Materials Needed






Color Spectrum Wheel Pattern Cardboard or illustration board
white screen
plastic filters (green, blue and red)
3 pieces of high intensity flashlights
Handle all sharp
TAKE
button fastener
Objects with
CARE!
glue or paste
care.
Procedure
Part 1: Color Wheel
1.
2.
3.
4.
Cut the two art files that make up the wheel on the next pages.
Cut along the lines drawn on the top wheel. Cut the 2 sides as shown. The
small window near the center of the wheel should be completely cut out and
removed.
Punch a hole at the center of the two wheels. You may use a button fastener to
secure the two wheels together one on top of the other, but they should be free
to rotate relative to each other.
When you see a region of the Color spectrum show up in the open window and
the "W,F,E" that correspond to that region showing up under the flaps then you
know that you have done it right.
180
181
182
Part 2: Characteristics of Light
1.
2.
3.
Try out your Color Spectrum Wheel by positioning the inner most of the flaps
on COLOR SPECTRUM. This will simultaneously position the other flaps to
ENERGY, WAVELENGTH & FREQUENCY.
Turn the upper wheel and observe the combinations.
Fill in the table below with the corresponding combinations you have observed
using your Spectrum Wheel.
Table 1. Characteristics of Color Lights
Color
Spectrum
Energy
(eV)
Frequency
(THz)
Wavelength
(nm)
Frequency x
wavelength
(m/s)
Red
Orange
Yellow
Green
Blue
Violet
4.
You will need to convert the equivalents of frequencies to Hz and the
equivalent wavelengths to meters. Note that terra (T) is a prefix for 1014 while
nano (n) is a prefix equivalent to 10 -9.
Q1. Which color registers the highest frequency? shortest wavelength?
Q2. Which color registers the lowest frequency? longest wavelength?
Q3. What do you observe with the wavelength and frequency of the different
colors?
Q4. What did you observe with the product of wavelength and frequency for each
color? What is the significance of this value?
Q5. What can you say about the speed of the different colors of light in air?
Q6. Give a plausible explanation as to why white light separate into different colors.
Part 3: Combining Colors
1.
2.
3.
Cover the lens of the flashlight with blue plastic filter. Do the same with the 2
other flashlights. The 2nd flashlight with green plastic filter and the 3rd with red
plastic filter.
Ask 2 other groupmates to hold the 2 other flashlight while you hold on to the
3rd one. Shine these flashlights on the white screen and note the colors
projected on the screen.
Let 2 color lights from the flashlights overlap. Observe what color is produced
and fill in the table below.
Table 2. Color that you see
Color of Plastic Filter
Green
Blue
Red
Color that you see projected on the screen
183
Table 3. Color Mixing
Color Combination
Green + Blue
Blue + Red
Red + Green
Red + Green + Blue
Resulting Color
Dispersion, a special kind of refraction, provided us color lights. This
phenomenon is observed when white light passes through a triangular prism. When
white light enters a prism and travels slower in speed than in vacuum, color
separation is observed due to variation in the frequencies (and wavelength) of color
lights. Remember the concept of refractive indices in the previous module? The
variations in frequencies (and wavelengths) are caused by the different refractive
indices of the varying color light. Thus, blue light with greater refractive index refracts
more and appears to bend more than red light. But do you really think that light will
bend when travelling in space? The last activity in this module will test your ability to
design an experiment to test if light travels in a straight line or not.
Activity 4
Light up straight!
Objective
In this activity, you should be able to design an experiment given several
materials to show that light travels in a straight line.
Materials Needed







2 pieces of cardboard
cutting tool
bright room
ruler or meter stick
permanent marker
pencil
any object (e.g. medium
size Johnson’s face
powder box)
TAKE
CARE!
Handle all sharp
objects with care.
Handle all lighting
tools with care to
avoid being burnt.
General Instructions
1.
2.
Given the materials design a 5-6 step procedure to test that light follows a
straight line or not.
Remember that you are only allowed to use the materials specified in this
particular activity.
184
3.
Check the rubric scoring for your guide.
Light Up Straight!
Rubric Scoring
Task/
Criteria
Experiment
Procedure
Result of
Experiment
Try-out/
Feasibility
Cooperation
and Team
Work
4
3
2
1
 Steps are
logically
presented.
 The procedure
included about
5-6 steps.
 All materials
given to the
group are
utilized in the
procedure
The group has
successfully
attained the object
to prove that light
travels in a straight
line using their
designed
procedure.
 Steps are
logically
presented.
 The procedure
included about
3-4 steps.
 75% of the
materials given
to the group
are utilized in
the procedure
The group has
attained the object
to prove that light
travels in a straight
line using their
designed
procedure but
there are some
steps that are not
very clear.
About 75% of the
members
completed their
task so as to
come up with the
expected output.
 Steps are
logically
presented.
 The procedure
included about
3-4 steps.
 50% of the
materials given
to the group
are utilized in
the procedure
The group has
partially attained
the object to prove
that light travels in
a straight line
using their
designed
procedure.
 Steps are
logically
presented.
 The procedure
included about
2-3 steps.
 25% of the
materials given
to the group
are utilized in
the procedure
The group had
some effort but
was not able to
attained the object
to prove that light
travels in a straight
line using their
designed.
About 50% of the
members
completed their
task so as to
come up with the
expected output.
About 25% of the
members did
his/her job
Each one of them
completed their
task so as to come
up with the
expected output.
Score
TOTAL:
Light, accordingly has wavelike nature and particle-like nature. As a wave, it
is part of the electromagnetic waves as the visible spectrum. This visible spectrum is
also known as white light. White light undergoes dispersion when it passes through a
prism. The variations of refractive indices result to variations in the refraction of color
lights dependent on the frequencies (and wavelength) of the color lights. This brings
about blue light being refracted more than the other color lights and thus appears to
be bent. However, light travels in a straight line path in a particular medium.
Brightness or intensity and colors are special properties of light. These can
be observed in different phenomena such as rainbows, red sunset, and blue sky.
You can identify many other applications of light and colors as you become keen
observers of natural phenomena.
Reading Materials/Links/Websites
http://amazing-space.stsci.edu/resources/explorations/groundup/
lesson/glossary/term-full.php?t=dispersion
http://www.physicsclassroom.com/class/refrn/u14l4a.cfm
185
Suggested time allotment: 5 to 6 hours
Unit 3
MODULE
5
HEAT
For sure, you have used the word ‘heat’ many times in your life. You have
experienced it; you have observed its effects. But have you ever wondered what heat
really is?
In your earlier grades, you learned that heat moves from the source to other
objects or places. Example is the kettle with water placed on top of burning stove.
The water gets hot because heat from the burning stove is transferred to it.
This module aims to reinforce your understanding of heat as an energy that
transfers from one object or place to another. You will determine the conditions
necessary for heat to transfer and the direction by which heat transfers by examining
the changes in the temperature of the objects involved. You will observe the different
methods of heat transfer and investigate some factors that affect these methods. The
results will help you explain why objects get hot or cold and why some objects are
seemingly colder or warmer than the others even if they are exposed to the same
temperature.
How is heat transferred between objects or places?
Do all objects equally conduct, absorb, or emit heat?
What is Heat?
Have you ever heard of the term “thermal energy” before? Any object is said
to possess thermal energy due to the movement of its particles. How is heat related
to thermal energy? Like any other forms of energy, thermal energy can be
transformed into other forms or transferred to other objects or places. Heat is a form
of energy that refers to the thermal energy that is ‘in transit’ or in the process of being
transferred. It stops to become heat when the transfer stops. After the energy is
transferred, say to another object, it may again become thermal energy or may be
transformed to other forms.
186
Thermometer
Heat transfer is related to
change in temperature or change in the
relative hotness or coldness of an
object. Most of the activities found in this
module will ask you to collect and
Figure 1. Thermometer
analyze temperature readings to arrive
at the desired concepts. To achieve this, you have to use the laboratory
thermometer, which is different from the clinical thermometer we use to determine
our body temperature. The kind that you most probably have in your school is the
glass tube with fluid inside, usually mercury or alcohol. Always handle the
thermometer with care to avoid breaking the glass. Also, be sure that you know how
to read and use the device properly to get good and accurate results. Inform your
teacher if you are not sure of this so that you will be guided accordingly.
Activity 1
Warm me up, cool me down
Objective
In this activity, you should be able to describe the condition necessary for
heat transfer to take place and trace the direction in which heat is transferred.
Materials Needed






2 small containers (drinking cups or glasses)
2 big containers (enough to accommodate the small containers)
tap water
hot water
food coloring
laboratory thermometers (with reading up to 100 oC)
Procedure
1.
Label the small and big containers
as shown in Figure 2.
2.
Half fill containers 1, 2, and A with
tap water. Half fill also container B
with hot water. Be careful when you
pour hot water into the container.
3.
Add few drops of food coloring on
the larger containers.
187
Figure 2
4.
Measure the initial temperature of
water in each of the 4 containers,
in degree Celsius (°C). Record
your measurements in Table 1.
5.
Carefully place container 1 inside
container A (Figure 3). This will be
your Setup 1.
6.
Place also container 2 inside
container B. This will be your
Setup 2.
7.
Measure the temperature of water in all containers 2 minutes after arranging
the setups. Record again your measurements in the table (after 2 minutes).
8.
Continue to measure and record the temperature of water after 4, 6, 8, and 10
minutes. Write all your measurements in the table below.
Setup 2
Setup 1
Figure 3
Table 1. Temperature readings for Setup 1 and Setup 2
Temperature (°C) of Water After
Container
Setup
1
Setup
2
0 min
(initial)
2
mins
4
mins
6
mins
8
mins
10
mins
1-Tap water
A-Tap water
2-Tap water
B-Hot water
Q1. In which setup did you find changes in the temperature of water inside the
containers? In which setup did you NOT find changes in the temperature of
water inside the containers?
Q2. In which setup is heat transfer taking place between the containers?
Q3. What then is the condition necessary for heat transfer to take place between
objects?
9.
Refer to the changes in the temperature of water in the setup where heat
transfer is taking place.
Q4. Which container contains water with higher initial temperature? What happens
to its temperature after 2 minutes?
Q5. Which container contains water with lower initial temperature? What happens
to its temperature after 2 minutes?
Q6. If heat is related to temperature, what then is the direction of heat that transfers
between the containers?
188
Q7. What happens to the temperature of water in each container after 4, 6, 8, and
10 minutes? What does this tell us about the heat transfer taking place
between the containers?
Q8. Until when do you think will heat transfer continue to take place between the
containers?
Temperature (°C)
If your teacher allows it, you may continue to measure the temperature of the
water in both containers for your basis in answering Q8. And if you plot the
temperature vs. time graph of the water in both containers, you will obtain a graph
similar to Figure 4.
Time (s)
Figure 4
10.
Q9.
Q10.
Q11.
Analyze the graph and answer the following questions:
What does the blue curved line on the graph show? Which container does
this represent?
What does the red curved line on the graph show? Which container does this
represent?
What does the orange broken line in the graph show? Is heat transfer still
taking place during this time? If yes, where is heat transfer now taking place?
If you do not have laboratory thermometers in your school, you may still
perform the activity above using your sense of touch. You can use your fingers or
hands to feel the objects being observed. But be very careful with this especially if
you are dealing with hot water. You have to take note also that touching is not
always reliable. Try out this simple activity below.
Prepare three containers. Half fill one container with hot water, but not
hot enough to burn your hand. Pour very cold water into the second
container and lukewarm water in the third container. First,
simultaneously place your left hand in the hot water and your right hand
in the cold water. Keep them in for a few minutes. Then take them out,
and place both of them together into the container with lukewarm water.
How do your hands feel? Do they feel equally cold?
189
If you try out this activity, you will observe that your left hand feels the water
cold while your right hand feels it warm. This is due to the initial conditions of the
hands before they were placed into the container with lukewarm water. So if you use
sensation to determine the relative hotness or coldness of the objects, make sure to
feel the objects with different hands or fingers.
How Does Heat Transfer?
In the previous activity, you explored the idea that heat transfers under
certain conditions. But how exactly is heat transferred? The next activities will allow
you to explore these different methods by which heat can be transferred from one
object or place to another.
Activity 2
Which feels colder?
Objective
In this activity, you should be able to describe heat transfer by conduction
and compare the heat conductivities of materials based on their relative coldness.
Materials Needed


small pieces of different objects (copper/silver coin, paper, aluminum foil, iron
nail, etc.)
laboratory thermometer
Procedure
Part A: To be performed one day ahead.
1.
Place a laboratory thermometer inside the freezer of the refrigerator.
2.
Place also your sample objects inside the freezer at the same time. Leave
them inside the freezer overnight.
Part B: To be performed the next day.
3.
Take the temperature reading from the thermometer inside the freezer.
Q1. What is the temperature reading inside the freezer?
Q2. If ever there is a way to measure also the temperature of the objects placed
inside the freezer, how do you think will their temperature compare with each
other and with the temperature reading from the thermometer?
190
4.
Touch one object lightly with your finger and feel it.
Q3. Did heat transfer take place between your finger and the object? If yes, how
and in what direction did heat transfer between them?
Q4. Did you feel the object cold? What made it so? (Relate this to your answer in
Q3.)
5.
Touch the rest of the objects inside the freezer using different fingers, then
observe.
Q5. Did the objects feel equally cold? What does this tell us about the amount of
heat transferred when you touch each object?
Q6. Which among the objects feels ‘coldest’? Which feels ‘warmest’?
Q7. Which among the objects is the best conductor of heat? Which object is the
poorest conductor of heat?
Activity 2 demonstrates heat transfer by conduction, one of the methods by
which heat is transferred. Conduction takes place between objects that are in contact
with each other. The energy from the object of higher temperature is transferred to
the other object through their particles that are close or in contact with each other.
Then the particles receiving the energy will also transfer the energy to other places
within the object through their neighboring particles. During this process, only the
energy moves, not the matter itself. This can be observed in Activity 1. You have
observed that the hot colored water stayed inside container B and did not mix with
the water inside container 2. So this shows that only the energy transferred between
the containers.
Here is another example of heat transfer by conduction. Think of a metal
spoon put in a bowl of a hot champorado that you were about to eat when you
suddenly remembered that you had to do first a very important task. When you came
back, you noticed that the handle of the spoon became really hot! How do you think
this happened? The heat from the champorado is transferred to the part of the
spoon that is in direct contact with the food by conduction. Then it is transferred to
the cooler regions of the spoon through its particles. Why did you feel the spoon hot?
When you touched the spoon, heat is also transferred to your hand by conduction.
So your hand gained heat or thermal energy, and this makes you feel the object hot.
Can you now explain why your hand that was previously dipped into hot
water felt the lukewarm water cold while the other hand that was previously dipped
into very cold water felt it hot?
Heat Conductivities
In the previous activity, you found out that some objects conduct heat faster
than the others. This explains why we feel some objects colder or warmer than the
others even if they are of the same temperature. Which usually feels warmer to our
feet – the tiled floor or the rug?
More accurate and thorough experiments had been carried out long before to
determine the heat or thermal conductivity of every material. The approximate values
of thermal conductivity for some common materials are shown below:
191
Table 2: List of thermal conductivities of common materials
Conductivity
Material
Material
W/(m·K)
Silver
429
Concrete
Copper
401
Water at 20°C
Gold
318
Rubber
Aluminum
237
Polypropylene plastic
Ice
2
Wood
Glass, ordinary
1.7
Air at 0°C
Conductivity
W/(m·K)
1.1
0.6
0.16
0.25
0.04 - 0.4
0.025
Solids that conduct heat better are considered good conductors of heat while
those which conduct heat poorly are generally called insulators. Metals are mostly
good conductors of heat. When we use a pot or pan to cook our food over a stove,
we usually use a pot holder made of fabrics to grasp the metal handle. In the
process, we are using an insulator to prevent our hand from being burned by the
conductor, which is the metal pan or pot. Why are woven fabrics that are full of
trapped air considered good insulators?
Activity 3
Move me up
You have previously learned that water is a poor conductor of heat, as shown
in Table 2. But why is it that when you heat the bottom of the pan containing water,
the entire water evenly gets hot quickly? Think of the answer to this question while
performing this next activity.
Objective
In this activity, you should be able to observe and describe convection of heat
through liquids.
Materials Needed





2 transparent containers (drinking glass, beaker, bottle)
dropper
hot water
cold water
piece of cardboard
Be careful not to bump the table or shake the container at any time during the
experiment.
Procedure
1.
Fill one of the glass containers with tap water.
192
2.
While waiting for the water to become still, mix in a separate container a few
drops of food coloring with a small amount of very cold water. (You may also
make the food coloring cold by placing the bottle inside the refrigerator for at
least an hour before you perform the activity.)
3.
Suck a few drops of cold food coloring using the dropper and slowly dip the end
of the medicine dropper into the container with tap water, down to the bottom.
See to it that the colored water does not come out of the dropper yet until its
end reaches the bottom of the container.
4.
Slowly press the dropper to release a small amount of the liquid at the bottom
of the container. Then slowly remove the dropper from the container, making
sure not to disturb the water. Observe for few minutes.
Q1. Does the food coloring stay at the bottom of the container or does it mix with
the liquid above it?
5.
Fill the other container with hot water.
6.
Place the cardboard over the top of the container with
hot water. Then carefully place the container with tap
water on top of it. The cardboard must support the
container on top as shown in Figure 5.
What happens to the food coloring after placing the
container above the other container? Why does this
happen?
How is heat transfer taking place in the setup? Where is
heat coming from and where is it going?
Is there a transfer of matter, the food coloring, involved
Figure 5
during the transfer of heat?
You have just observed another method of heat transfer, called convection. In
your own words, how does convection take place? How is this process
different from conduction?
Do you think convection only occurs when the source of heat is at the bottom
of the container? What if the source of heat is near the top of the container?
You may try it by interchanging the containers in your previous experiment.
Q2.
Q3.
Q4.
Q5.
Q6.
What you found out in this experiment is generally true with fluids, which
include liquids and gases. In the next quarter, you will learn about convection of heat
in air when you study about winds.
So what happens in your experiment? When you placed the glass on top of
another glass with hot water, heat transfer takes place from the hot water to the tap
water including the colored water. This makes these liquids expand and become
lighter and float atop the cooler water at the top of the container. This will then be
replaced by the cooler water descending from above.
193
Activity 4
Keep it cold
So far you have learned that heat can be transferred by conduction and
convection. In each method, a material, either a solid or a liquid or gas, is required.
But can heat also transfer even without the material? If we stay under the sun for a
while, do we not feel warm? But how does the heat from this very distant object
reach the surface of the earth? The transfer of energy from the sun across nearly
empty space is made possible by radiation. Radiation takes place even in the
absence of material.
Do you know that all objects, even ordinary ones, give off heat into the
surrounding by radiation? Yes, and that includes us! But why don't we feel it? We do
not feel this radiation because we are normally surrounded by other objects of the
same temperature. We can only feel it if we happen to stand between objects that
have different temperature, for example, if we stand near a lighted bulb, a burning
object, or stay under the Sun.
All objects emit and absorb radiation although some objects are better at
emitting or absorbing radiation than others. Try out this next activity for you to find
out. In this activity, you will determine how different surfaces of the object affect its
ability to absorb heat.
Introduction
One hot sunny day, Cobi and Mumble walked into a tea shop and each asked
for an order of iced milk tea for takeout. The crew told them as part of their promo,
their customers can choose the color of the tumbler they want to use, pointing to the
array of containers made of the same material but are of different colors and
textures. Cobi favored the container with a dull black surface, saying that the milk tea
will stay cooler if it is placed in a black container. Mumble remarked that the tea
would stay even cooler if it is in a container with bright shiny surface.
Prediction
1.
2.
If you were in their situation, which container do you think will keep the iced
milk tea cooler longer? Explain your choice.
Assuming an initial temperature of 5°C, predict the possible temperatures of the
milk tea in each container after 5, 10, 15, and 20 minutes. Assume that the
containers are covered.
Cup
Dull black
container
Bright shiny
container
0 min
Temperature (°C)
5 min
10 min
15 min
5°C
5°C
194
20 min
Task:
Design a laboratory activity that will enable you to test your prediction. See to it that
you will conduct a fair investigation. Start by answering the questions below:

What problem are you going to solve? (Testable Question)

What are you going to vary? (Independent variable)

What are you not going to vary? (Controlled Variables)

What are you going to measure? (Dependent variables)
1.
Write down your step by step procedure. Note that you may use the light from
the sun or from the lighted bulb as your source of energy.
2.
Collect your data according to your procedure. Present your data in tabulated
form.
3.
Analyze your data and answer the following questions:
Q1.
Q2.
Q3.
Q4.
Which container warmed up faster?
Which container absorbs heat faster?
Which container will keep the milk tea cooler longer? Is your prediction correct?
Will the same container also keep a hot coffee warmer longer that the other?
Activity 5
All at once
So far, you have learned that heat can be transferred in various ways. You
have also learned that different objects absorb, reflect, and transmit heat differently.
In the next activities, you will not perform laboratory experiments anymore. All you
have to do is to use your understanding so far of the basic concepts of heat transfer
to accomplish the given tasks or answer the questions being asked.
Task 1
Heat transfer is evident everywhere around us. Look at the illustration below.
This illustration depicts several situations that involve heat transfer. Your task is to
identify examples of situations found in the illustration that involve the different
methods of heat transfer.
195
Figure 6
1.
Encircle three situations in the drawing that involve any method of heat
transfer. Label them 1, 2, and 3.
2.
Note that in your chosen situations, there could be more than one heat transfer
taking place at the same time. Make your choices more specific by filling up
Table 3.
Table 3: Examples of heat transfer
Description
Which object
gives off heat?
1
2
3
196
Which object
receives heat?
What is the
method of heat
transfer?
Task 2
Below is a diagram showing the basic parts of the thermos bottle. Examine
the parts and the different materials used. Explain how these help to keep the liquid
inside either hot or cold for a longer period of time. Explain also how the methods of
heat transfer are affected by each material.
Stopper made of
plastic or cork
Silvered inner
and outer glass
wall
Hot
liquid
Vacuum
between inner
and outer wall
Outer casing
made of plastic
or metal
Ceramic base
Figure 7: Basic
parts of a thermos
bottle
In the next module, you will learn about another form of energy which you
also encounter in everyday life, electricity. Specifically, you will learn about the
different types of charges and perform activities that will demonstrate how objects
can be charged in different ways. You will also build simple electric circuits and
discuss how energy is transferred and transformed in the circuit.
Links and References
Sootin, H. (1964). Experiments with heat. W.W. Norton and Company, Inc.
Where is Heat coming from and where is it going? Retrieved March 10, 2012 from
http://www.powersleuth.org/docs/EHM%20Lesson%204%20FT.pdf
Conduction, Convection, Radiation: Investigating Heat Transfers. Retrieved March
10, 2012 from http://www.powersleuth.org/docs/EHM%20Lesson%205%20FT.pdf
197
Suggested time allotment: 5 to 6 hours
Unit 3
MODULE
6
ELECTRICITY
In Module 5, you learned about heat as a form of energy that can be
transferred through conduction, convection and radiation. You identified the
conditions that are necessary for these processes to occur and performed activities
that allowed you to investigate the different modes of heat transfer. Finally, you
learned to distinguish between insulators and conductors of heat and were able to
identify the uses of each.
Now you will learn about another form of energy which you encounter in
everyday life, electricity. You must be familiar with this energy since it is the energy
required to operate appliances, gadgets, and machines, to name a few. Aside from
these manmade devices, the ever-present nature of electricity is demonstrated by
lightning and the motion of living organisms which is made possible by electrical
signals sent between cells. However, in spite of the familiar existence of electricity,
many people do not know that it actually originates from the motion of charges.
In this module, you will learn about the different types of charges and perform
activities that will demonstrate how objects can be charged in different ways. You will
also learn the importance of grounding and the use of lightning rods. At the end of
the module you will do an activity that will introduce you to simple electric circuits.
The key questions that will be answered in this module are the following:
What are the different types of charges?
How can objects be charged?
What is the purpose of grounding?
How do lighting rods work?
What constitutes a complete electrical circuit?
198
Activity 1
Charged interactions
Objectives
After performing this activity, you should be able to:
1.
2.
3.
4.
charge a material by friction;
observe the behavior of charged objects;
distinguish between the two types of charges; and
demonstrate how objects can be discharged.
Materials Needed:





Strong adhesive tape (transparent)
Smooth wooden table
Meter stick
Piece of wood (~1 meter long) to hold tape strips
Moistened sponge
Procedure:
1.
Using a meter stick, pull off a 40- to 60- cm piece of adhesive tape and fold a
short section of it (~1 cm) to make a nonsticky "handle" at that end of the tape.
2.
Lay the tape adhesive side down and slide your finger along the tape to firmly
attach it to a smooth, dry surface of a table.
3.
Peel the tape from the surface vigorously pulling up on the handle you have
made on one end. See figure below. Make sure that the tape does not curl up
around itself or your fingers.
Figure 1. How to peel the tape off the surface
4.
While holding the tape up by the handle and away from other objects, attach
the tape to the horizontal wooden piece or the edge of your table. Make sure
that the sticky side does not come in contact with other objects.
199
Figure 2. Attaching the tape to a holder
5.
Bring your finger near, but not touching, the nonsticky side of the tape. Is there
any sign of interaction between the tape and the finger?
6.
Try this with another object. Is there any sign of interaction between the tape
and this object?
7.
Prepare another tape as described in steps 1 to 3.
8.
Bring the nonsticky side of the two charged tapes you prepared near each
other. Do you observe any interaction?
9.
Drag a moistened sponge across the nonsticky side of the tapes and repeat
steps 5, 6 and 8. Do you still observe any interaction?
10.
Record your observations.
Types of Charges
You have learned in previous modules that all matter are made up of atoms
or combinations of atoms called compounds. The varying atomic composition of
different materials gives them different electrical properties. One of which is the
ability of a material to lose or gain electrons when they come into contact with a
different material through friction.
In activity 1, when you pulled the tape vigorously from the table, some of the
electrons from the table’s surface were transferred to the tape. This means that the
table has lost some electrons so it has become positively charged while the tape
has gained electrons which made it negatively charged. The process involved is
usually referred to as charging up the material, and in this particular activity the
process used is charging by friction.
200
It is important to remember that during the charging process, ideally, the
amount of charge lost by the table is equal to the amount of charge gained by the
tape. This is generally true in any charging process. The idea is known as:
The Law of Conservation of Charge
Charges cannot be created nor destroyed, but can be
transferred from one material to another.
The total charge in a system must remain constant.
Electric Force
When you brought your finger (and the other object) near the charged tape,
you must have observed that the tape was drawn towards your finger as if being
pulled by an invisible force. This force is called electric force which acts on charges.
An uncharged or neutral object that has balanced positive and negative charges
cannot experience this force.
We learned from the previous section that the tape is negatively charged. The
excess negative charge in the tape allowed it to interact with your finger and the
other object. Recall also that when you placed the two charged tapes near each
other they seem to push each other away. These observations tell us that there are
two kinds of electric force which arises from the fact that there also two kinds of
electrical charges. The interactions between the charges are summarized in the
following law:
Electrostatic Law
Like charges repel and unlike charges attract.
But your finger and the other object are neutral, so how did they interact with
the charged tape? Generally, a charged object and an uncharged object tend to
attract each other due to the phenomenon of electrostatic polarization which can be
explained by the electrostatic law. When a neutral object is placed near a charged
object, the charges within the neutral object are rearranged such that the charged
object attracts the opposite charges within the neutral object. This phenomenon is
illustrated in Figure 3.
201
Figure 3. Polarization of a neutral object
Discharging
In Activity 1, after dragging a moistened sponge on the surface of the tape,
you must have noticed that the previous interactions you observed has ceased to
occur. What happened? The lack of interaction indicates that the electrical force is
gone which can only happen when there are no more excess charges in the tape,
that is, it has become neutral.
The process of removing excess charges on an object is called discharging.
When discharging is done by means of providing a path between the charged object
and a ground, the process may be referred to as grounding. A ground can be any
object that can serve as an “unlimited” source of electrons so that it will be capable of
removing or transferring electrons from or to a charged object in order to neutralize
that object.
Grounding is necessary in electrical devices and equipment since it can
prevent the build-up of excess charges where it is not needed. In the next activity,
you will use the idea of grounding to discover another way of charging a material.
Activity 2
To charge or not to charge
Objective
After performing this activity, you should be able to apply the phenomenon of
polarization and grounding to charge a material by induction.
Materials Needed:



Styrofoam cup
soft drink can
balloon
202
Procedure:
1.
Mount the soft drink can on the Styrofoam cup as seen in
Figure 4.
Figure 4. Mounting of
soft drink can
2.
Charge the balloon by rubbing it off your hair or
your classmate’s hair. Note: This will work only if
the hair is completely dry.
3.
Place the charged balloon as near as possible to
the soft drink can without the two objects touching.
Figure 5. Balloon placed
near the can
4.
Touch the can with your finger at
the end opposite the balloon.
5.
Remove your hand and observe
how the balloon and the can will
interact.
Figure 6. Touching the can
Q1. What do you think is the charge acquired by the balloon after rubbing it against
your hair?
Q2. In which part of the activity did polarization occur? Explain.
Q3. What is the purpose of touching the can in step #4?
Q4. Were you able to charge the soft drink can? Explain how this happened.
Q5. Based on your answer in Q1, what do you think is the charge of the soft drink
can?
203
Conductors vs. Insulators
The behavior of a charged material depends on its ability to allow charges to
flow through it. A material that permits charges to flow freely within it, is a good
electrical conductor. A good conducting material will allow charges to be distributed
evenly on its surface. Metals are usually good conductors of electricity.
In contrast to conductors, insulators are materials that hinder the free flow
charges within it. If charge is transferred to an insulator, the excess charge will
remain at the original location of charging. This means that charge is seldom
distributed evenly across the surface of an insulator. Some examples of insulators
are glass, porcelain, plastic and rubber.
The observations you made had in Activity 2 depended on the fact that the
balloon and the Styrofoam are good insulators while the soft drink can and you are
good conductors. You have observed that the soft drink can has become charged
after you touched one of its ends. The charging process used in this activity is called
induction charging, where an object can be charged without actual contact to any
other charged object.
In the next activity you will investigate another method of charging which
depends on the conductivity of the materials
Activity 3
Pass the charge
Objective
After performing this activity, you should be able to charge a material by
conduction.
Materials Needed:



2 styrofoam cups
2 softdrink cans
balloon
Procedure:
1.
Repeat all steps of Activity 2.
2.
Let the charged can-cup set-up from
Activity 2 touch a neutral can-cup set-up
as shown in Figure 7.
204
Figure 7. Putting the two
set-ups into contact.
3.
Separate the two set-ups then observe how the charged balloon interacts with
the first and second set-up.
Q1. Were you able to charge the can in the second set-up? Explain how this
happened.
Q2. s it necessary for the two cans to come into contact for charging to happen?
Why or why not?
Q3. From your observation in step 3, infer the charge acquired by the can in the
second set-up.
The charging process you performed in Activity 3 is called charging by
conduction which involves the contact of a charged object to a neutral object. Now
that you have learned the three types of charging processes, we can discuss a
natural phenomenon which is essentially a result of electrical charging. You will
investigate this phenomenon in the following activity.
Activity 4
When lightning strikes
Objectives:
After performing this activity, you should be able to:
1. explain how lightning occurs;
2. discuss ways of avoiding the dangers associated with lightning; and
3. explain how a lightning rod functions.
Materials Needed: access to reference books or to the Internet
Procedure:
1.
Learn amazing facts about lightning by researching the answers to the
following questions:
 What is a lightning?
 Where does a lightning originate?
 How ‘powerful’ is a lightning bolt?
 Can lightning’s energy be caught stored, and used?
 How many people are killed by lightning per year?
 What can you do to prevent yourself from being struck by lightning?
 Some people have been hit by lightning many times. Why have they
survived?
 How many bushfires are started by lightning strikes?
 ‘Lightning never strikes twice in the same place.’ Is this a myth or a fact?
 What are lightning rods? How do they function?
205
As introduced at the beginning of this module, electrical energy has
numerous applications. However many of this applications will not be possible unless
we know how to control electrical energy or electricity. How do we control electricity?
It starts by providing a path through which charges can flow. This path is provided by
an electric circuit. You will investigate the necessary conditions for an electric
circuit to function in the following activity.
Activity 5
Let there be light!
Objectives:
After performing this activity, you should be able to:
1.
2.
identify the appropriate arrangements of wire, bulb and battery which
successfully light a bulb; and
describe the two requirements for an electric circuit to function.
Materials Needed:




3- or 1.5-volt battery
2-meter copper wires/ wires with alligator clips
pliers/ wire cutter
1.5- watt bulb/ LED
Procedure:
1.
Work with a partner and discover the appropriate arrangements of wires, a
battery and a bulb that will make the bulb light.
2.
Once you are successful in the arrangement, draw a diagram representing
your circuit.
3.
Compare your output with other pairs that are successful in their arrangement.
Q1. What difficulties did you encounter in performing this activity?
Q2. How does your work compare with other pair’s work?
Q3. What was necessary to make the bulb light?
206
Energy Transfer in the Circuit
In Activity 5, you have seen that with appropriate materials and connections,
it is possible for the bulb to light. We know that light is one form of energy. Where did
this energy come from? The law of conservation of energy tells us that energy can
neither be created nor destroyed but can be transformed from one form to another.
This tells us that the light energy observed in the bulb must have come from the
electrical energy or electricity in the circuit. In fact, all electrical equipment and
devices are based on this process of transformation of electrical energy into other
forms of energy. Some examples are:
1. Flat iron – Electrical energy to thermal energy or heat
2. Electric fan – Electrical energy to mechanical energy
3. Washing machine – electrical energy to mechanical energy.
Can you identify other examples?
References
“Instructor Materials: Electricity” by American Association of Physics Teachers ©
2001. Retrieved from https://aapt.org/Publications/pips_samples/
2_ELECTRICITY/INSTRUCTOR/099_e4.pdf
http://www.physicsclassroom.com/class/estatics/U8L2a.cfm
http://museumvictoria.com.au/pages/7567/lightning-room-classroom-activities.pdf
http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html
207
208
Suggested time allotment: 14 hours
Unit 4
MODULE
1
THE PHILIPPINE
ENVIRONMENT
Overview
Everything that we see around us makes up our environment. The landforms
and bodies of water that make up the landscape, the mountains and valleys, rivers
and seas; the climate, the rains brought by the monsoons, the warm, humid weather
that we frequently experience; the natural resources that we make use of; every
plant and animal that live around us. Truly, the environment is made up of a lot of
things.
All these things that we find in our surroundings and all the natural
phenomena that we observe are not due to some random luck or accident. What
makes up our environment is very much related to where our country is on the globe.
Or, to say it in a different way, the characteristics of our environment are determined
by the location of the Philippines on the planet.
Latitude and Longitude
Before we learn about the characteristics of our environment, let us first talk
about the location of the Philippines. Where is the Philippines? The Philippines is on
Earth, of course, but where exactly is it located? To answer this question, you have
to learn a new skill: locating places using latitude and longitude.
Activity 1
Where in the world is the Philippines? (Part I)
Objective
After performing this activity, you should be able to describe the location of
the Philippines using latitude and longitude.
What to use
globes
209
What to do
1. Study the image of a globe on the right. Then
get a real globe and identify the parts that are
labelled in the image. Be ready to point them
out when your teachers asks you.
2. After studying the globe and the image on the
right, try to define “equator” in your own
words. Give your own definition when your
teacher asks you.
3. The “northern hemisphere” is that part of the
world between the North Pole and the
equator. Show the northern hemisphere on
the globe when your teacher asks you.
4. Where is the “southern hemisphere”? Show
the southern hemisphere on the globe when
your teacher asks you.
Figure 1. What does the
globe represent?
5. Study the drawing on the right. It shows the lines of latitude.
Q1. Describe the lines of latitude.
Q2. Show the lines of latitude on the
globe when your teacher asks you.
Q3. The starting point for latitude is the
equator. The equator is at latitude 0°
(0 degree). At the North Pole, the
latitude is 90°N (90 degrees north).
At the South Pole, the latitude is
90°S (90 degrees south). Show the
following latitudes when your teacher
calls on you: 15°N; 60°N; 30°S;
45°S.
Q4. The globe does not show all lines of
latitude. If
you
wish
to
find
50°N, where should you look?
210
Figure 2. What is the reference
line when determining the
latitude?
6. Study the drawing on the right. It shows the lines of longitude.
Q5. Describe the lines of longitude.
Q6. Show the lines of longitude on the
globe when your teacher asks you.
Q7. The starting point for longitude is
the Prime Meridian. The Prime
Meridian is at longitude 0°. Show
the Prime Meridian on the globe
when your teacher asks you.
Q8. To the right of the Prime Meridian,
the longitude is written this way:
15°E (15 degrees east), 30°E (30
degrees east), and so on. To the
Figure 3. What is the
left of the Prime Meridian, the
reference line when
longitude is written as 15°W (15
determining the longitude?
degrees west), 30°W (30 degrees
west), and so on. On your globe, find longitude 180°. What does this
longitude represent?
Q9. Not all lines of longitude are shown on a globe. If you want to find 20°W,
where should you look?
Q10.
The location of a place may be described by using latitude and longitude.
To the nearest degree, what is the latitude and longitude of Manila?
Q11.
Compared to the size of the world, Manila is just a tiny spot, and its
location may be described using a pair of latitude and longitude. But how
would you describe the location of an “area” such as the whole
Philippines?
Now you know how to describe the location of a certain place using latitude
and longitude. The lines of latitude are also known as parallels of latitude. That is
because the lines of latitude are parallel to the equator and to each other. Five lines
of latitude have special names. They are listed in the table below. The latitude values
have been rounded off to the nearest half-degree.
Latitude
0°
23.5°N
23.5°S
66.5°N
66.5°S
Name
Equator
Tropic of Cancer
Tropic of Capricorn
Arctic Circle
Antarctic Circle
211
Get a globe and find the Tropic of Cancer and the Tropic of Capricorn. Trace
the two lines of latitude with a red chalk. The part of the world between the two chalk
lines is called the tropics. Countries that are located in this zone experience a
tropical climate where the annual average temperature is above 18°C.
Now, find the Arctic Circle and the Antarctic Circle on the globe. Trace them
with blue chalk. Between the Tropic of Cancer and the Arctic Circle is the northern
temperate zone; between the Tropic of Capricorn and the Antarctic Circle is the
southern temperate zone. Countries in these zones go through four seasons –
winter, spring summer, and autumn.
Finally, the areas within the Arctic Circle and Antarctic Circle are called the
polar regions or frigid zones. People who choose to live in these areas have to deal
with temperatures that never go above 10°C. It is cold all year round and even during
the summer months, it does not feel like summer at all.
To sum up, the closer the latitude is to the equator, the warmer the climate.
The closer it is to the poles, the colder. Thus, it is clear that there is a relationship
between the latitude of a place and the climate it experiences, and you will find out
why in the next module.
Landmasses and Bodies of Water
Using latitude and longitude is not the only way that you can describe the
location of a certain area. Another way is by identifying the landmasses and bodies
of water that are found in that area. So, what are the landmasses and bodies of
water that surround the Philippines? Do the following activity and get to know the
surrounding geography.
Activity 2
Where in the world is the Philippines? (Part II)
Objective
After performing this activity, you should be able to describe the location of
the Philippines with respect to the surrounding landmasses and bodies of
water.
What to use
globe or world map
What to do
1.
Using a globe or a world map as reference, label the blank map below.
212
2.
Your labelled map should include the following:
A. Landmasses
B. Bodies of water
Philippine archipelago
Asian continent
Malay peninsula
Isthmus of Kra
Indonesian archipelago
Australian continent
Philippine Sea
South China Sea
Indian Ocean
Pacific Ocean
Q1. Which bodies of water in the list are found to the west of the Philippines?
Q2. Which body of water in the list is located to the east of the Philippines?
Q3. Which large landmass is found to the north of the Philippines?
3.
Be ready to show the map with your labels when your teachers asks you.
Figure 4. Where is the Philippines in the map? Why is the Philippines
called an archipelago?
213
By now you can say that you really know where the Philippines is. You can
now describe its location in two ways: by using latitude and longitude, and by
identifying the landmasses and bodies of water that surround it. What then is the use
of knowing where the Philippines is located? You will find out in the next section and
also in the following module.
Are We Lucky in the Philippines?
Planet Earth is made up of different things - air, water, plants, animals, soil,
rocks, minerals, crude oil, and other fossil fuels. These things are called natural
resources because they are not made by people; rather they are gathered from
nature. Sunlight and wind are also natural resources. We use all these things to
survive or satisfy our needs.
The Philippines is considered rich in natural resources. We have fertile,
arable lands, high diversity of plant and animals, extensive coastlines, and rich
mineral deposits. We have natural gas, coal, and geothermal energy. Wind and
water are also harnessed for electricity generation.
Photo: Courtesy of Michael C. Tan
Photo: Courtesy of Kit Stephen S. Agad
Photo: Courtesy of Cecile N. Sales
Figure 5: What kind of natural resources are shown in the pictures? Do you
have similar resources in your area?
Why do we have rich natural resources? What geologic structures in the
country account for these bounty? Is our location near the equator related to the
presence of these natural resources?
The next lessons will help you find answers to some questions about natural
resources in the country namely, rocks and minerals, water, soil, varied life forms,
and energy.
 How does our latitude position affect the water, soil resources, and
biodiversity in the country?
 What mineral deposits do we have in the country? Where are they located
and why only in those places?
 Given our location, what energy resources are available?
 Which of our practices in using natural resources are sustainable? Which are
not sustainable?
214

How can we help conserve natural resources so that future generations can
also enjoy them?
Hopefully, the knowledge and skills acquired in the lessons will help you
value your responsibility as a productive citizen so that you can help prevent
protected and vulnerable places from being mined, forests from being overcut, and
natural resources like metals from ending up in a dumpsite.
Water Resources and Biodiversity
The Philippines boasts of many different kinds of natural water forms, such as
bays, rivers, lakes, falls, gulfs, straits, and swamps. Because it is made up of islands,
the country's coastline (seashore) if laid end-to-end, would measure around 17.5
thousand kilometers. And you know how we are proud of our coastlines! The bodies
of water and its surrounding environment not only support the survival of diverse
organisms for food but are also used for other economic activities. All these you
learned in Araling Panlipunan.
In the previous activity you identified two big bodies of water on the west and
east side of the country: the Pacific Ocean in the east and south China Sea in the
west (sometimes referred to as the West Philippine Sea). These bodies of water are
the origin of typhoons which on the average, according to Philippine Atmospheric,
Geophysical and Astronomical Services Administration (PAGASA), is about 20 a
year. Typhoons and the monsoons (amihan and habagat) bring lots of rain to the
Philippines.
What is your association with too much rainfall? For some, rain and typhoons
result in flooding, landslides, and health related-problems. But water is one of
nature’s gifts to us. People need fresh water for many purposes. We use water for
domestic purposes, for irrigation, and for industries. We need water to generate
electricity. We use water for recreation or its aesthetic value. Many resorts are
located near springs, waterfalls or lakes.
Where does water in your community come from? You collect them when the
rain falls or get them from the river, deep well, or spring. But where does water from
rivers, lakes, and springs originate?
They come from a watershed – an area of land on a slope which drains its
water into a stream and its tributaries (small streams that supply water to a main
stream). This is the reason why a watershed is sometimes called a catchment area
or drainage basin. It includes the surface of the land and the underground rock
formation drained by the stream.
From an aerial view, drainage patterns in a watershed resemble a network
similar to the branching pattern of a tree. Tributaries, similar to twigs and small
branches, flow into streams, the main branch of the tree. Streams eventually empty
into a large river comparable to the trunk.
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Photo: Courtesy of Michael C. Tan
Figure 6. The network of streams in a watershed area is illustrated on the left and a
photo of a watershed area is on the right. How does the concept “water runs
downhill” apply to a watershed?
Watersheds come in all shapes and sizes. They cross towns and provinces.
In other parts of the world, they may cross national boundaries.
There are many watersheds in the Philippines basically because we have
abundant rainfall. Do you know that Mt. Apo in Davao-Cotabato, Makiling-Banahaw
in Laguna and Quezon, and Tiwi in Albay are watersheds? You must have heard
about La Mesa Dam in Metro Manila, Pantabangan Dam in Pampanga, and Angat
Dam in Bulacan. These watersheds are sources of water of many communities in the
area. The Maria Cristina Falls in Iligan City is in a watershed; it is used to generate
electricity. Locate these places in your map. Ask elders where the watershed is in or
near your area? Observe it is used in your community.
But watersheds are not just about water. A single watershed may include
combination of forest, grassland, marshes, and other habitats. Diverse organisms in
the Philippines are found in these areas! Being a tropical country, the Philippines has
abundant rainfall, many bodies of water, and lots of sunshine. The right temperature
and abundant rainfall explain partly why our country is considered to be a megadiverse country. This means that we have high diversity of plants and animals, both
on land and in water (Philippine Clearing House Mechanism Website, 2012).
Reports show that in many islands of the Philippine archipelago, there is a
high number of endemic plants and animals (endemic means found only in the
Philippines). The country hosts more than 52,177 described species of which more
than half is found nowhere else in the world. They say that on a per unit area basis,
the Philippines shelters more diversity of life than any other country on the planet.
For now remember that the main function of a watershed is the production of
a continuous water supply that would maintain the lifeforms within it and in the area
fed by its stream. Later you will learn that besides supporting the survival of varied
life forms, abundant water in the country is important in moderating temperature.
This topic will be discussed later.
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Have you ever asked yourself the following questions? If we have abundant
rainfall to feed watersheds, why do we experience drought some parts of the year?
What factors affect the health of a watershed? Is there a way of regulating the flow of
water in watershed so that there will be enough for all throughout the year? What can
people do to keep watersheds ‘healthy’? Find out about these in the next activity.
Activity 3
What are some factors that will affect the
amount of water in watersheds?
Objective
You will design a procedure to show how a certain factor affects the amount
of water that can be stored underground or released by a watershed to rivers,
lakes and other bodies of water.
What to do
1.
In your group, choose one factor that you want to investigate.
a.
b.
c.
d.
Vegetation cover
Slope of the area
Kind of soil
Amount of rainfall
2.
Identify the variables that you need to control and the variable that you will
change.
3.
Design a procedure to determine the effect of the factor you chose on
watersheds.
4.
Be ready to present your design in the class and to defend why you designed it
that way.
Soil Resources, Rainfall and Temperature
Recall in elementary school science that soil is formed when rocks and other
materials near the Earth’s surface are broken down by a number of processes
collectively called weathering. You learned two types of weathering: the mechanical
breaking of rocks or physical weathering, and the chemical decay of rocks or
chemical weathering.
Let us review what happens to a piece of rock when left under the Sun and
rain for a long time. Do the next activity.
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Activity 4
How are soils formed from rocks?
Objectives
1.
2.
Using the information in the table, trace the formation of soil from rocks.
Identify the factors acting together on rocks to form soil.
What to use
Drawing pens
What to do
1. Processes involved in soil formation are listed in the table below. Read the
descriptions of the processes and make your own illustrations of the different
processes. Draw in the designated spaces.
2. Use the descriptions and your drawings to answer the following questions.
Q1. What are the factors that act together on rocks to form soil?
Q2. What does the following sentence mean, “Soils were once rocks”?
Processes of soil formation
When a piece of rock is exposed
to the Sun, its outer part expands
(becomes bigger) because it
heats up faster than the inner
part (Drawing A).
Illustrations of processes
Drawing A
On cooling, at night time, the
outer part of the rock contracts or
shrinks because the outer part of
the rock cools faster than the
inner portion (Drawing B). The
process of expansion and
contraction are repeated over the
years and produce cracks in the
rock causing the outer surface to
break off.
Once broken, water enters the
cracks causing some minerals to
dissolve. The rock breaks apart
further. (Drawing C).
Drawing B
Drawing C
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Processes of soil formation
Air also enters the cracks, and
oxygen in the air combines with
some elements such as iron to
produce iron oxide (rust or
kalawang) which is brittle and will
easily peel off. In a similar way,
carbon dioxide from the air reacts
with water to form an acid
causing the rock to soften further.
Once soft and broken, bacteria
and small plants start to grow in
the cracks of the rock (Drawing
D).
Illustrations of processes
Drawing D
After some time, the dead plants
and animals die and decay
causing the formation of more
acidic substances which further
breaks the rocks. The dead
bodies of plants and animals are
acted upon by microorganism
and breakdown into smaller
compounds while the minerals
from the rock return to the soil.
Soil covers the entire Earth. Temperature, rainfall, chemical changes, and
biological action act together to continuously form soil. Climate, expressed as both
temperature and rainfall effects, is often considered the most powerful soil-forming
factor.
Temperature controls how fast chemical reactions occur. Many reactions
proceed more quickly as temperature increases. Warm-region soils are normally
more developed or more mature than cold-region soils. Mature soils have more silt
and clay on or near the surface. Thus, soils in the tropical areas are observed to
sustain various farming activities and account for why the primary source of
livelihood in the Philippines and other countries in the tropical region is their fertile
land. What is the effect of very little rainfall on food production?
Climate (temperature and rainfall) is a significant factor not only in soil
formation but also in sustaining diversity of plants and animals in the country. On the
other hand, water also directly affects the movement of soluble soil nutrients from the
top soil to deep under the ground (leaching). These nutrients may no longer be
available to shallow rooted plants. Acidic rainwater may also contribute to the loss of
minerals in soil resulting in low yield. So rainfall determines the kind of vegetation in
an area. In turn, the degree of vegetation cover, especially in sloping areas,
determines how much soil is removed. Are there ways to protect soil resources?
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Rocks and Mineral Resources
History tells us that rocks have been used by humans for more than two
million years. Our ancestors lived in caves; they carved rocks and stones to make
tools for hunting animals, cultivating crops, or weapons for protection. Rocks, stones,
gravel, and sand were and are still used to make roads, buildings, monuments, and
art objects.
http://commons.wikimedia.org/wiki/File:DirkvdM_rocks.jpg
http://en.wikipedia.org/wiki/File:Pana_Banaue_Rice_Terr
aces.jpg
Figure 7. What are the features of the
rocks? What environmental factors
may have caused such features?
Figure 8. What kind of tools do you
think were used to build the Rice
Terraces? Why are terraces useful?
The mining of rocks for their metal content has been considered one of the
most important factors of human progress. The mining industry has raised levels of
economy in some regions, in part because of the kind of metals available from the
rocks in those areas.
Activity 5
Where are the mineral deposits in the
Philippines?
Mineral deposits can be classified into two types: metallic and non-metalllic.
You have already learned the symbols of some metals and nonmetals. Review them
before you do the activity.
Objectives
After performing this activity, you will be able to
1. locate the metallic mineral deposits across the country;
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2. find out what geologic features are common in areas where the deposits are
found;
3. give a possible reason/s for the association between metallic mineral deposits
and geologic features in the country; and
4. infer why your area or region is rich or not rich in metallic mineral deposits.
What to use
Figure 9: Metallic Deposits Map of the Philippines
Figure 10: Map of Trenches and Faults in the Philippines
Figure 11: Map of Volcanoes in the Philippines
2 pieces of plastic sheet used for book cover, same size as a book page
Marking pens (two colors, if possible)
What to do
Part I
1. Familiarize yourself with the physical map of the Philippines. Identify specific
places of interest to you in the different regions.
2. In your notebook, make a four-column table with headings similar to Table 1.
Table 1: Metallic Minerals in the Philippines and Their Location
Geologic
Metal, in
Metal, in Words Province/Region Structure Near
Symbols
Where the
the Location of
(Example: Au)
Metals are
the Metallic
Found
Deposits
(1)
(2)
(3)
(4)
3. As a group, study the Metallic Deposits Map of the Philippines. See Figure 9. In
the map you will see symbols of metals. Fill in the information needed in
Columns 1 and 2 of your own table.
4. Check with each other if you have correctly written the correct words for the
symbol of the metals. Add as many rows as there are kinds of metals in the map.
5. Analyze the data in Table 1.
Q1. Identify five metals which are most abundant across the country. Put a number
on this metal (1 for most abundant, 2 next abundant, and so on).
Q2. Record in Column 3 where the five most abundant metals are located.
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Figure 9. Metallic Deposits in the Philippines
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Figure 10. Trenches and Faults in the Philippines
223
Figure 11. Volcanoes in the Philippines
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Part II
1.
Get two plastic sheets. On one sheet, trace the outlines of the trenches and
faults from Figure 10. On the other sheet, trace the location of volcanoes from
Figure 11.
2.
Place the Trench and Fault plastic sheet over the Metallic Deposits map.
3.
Place the Volcanoes plastic sheet over the two maps.
Q3. What geologic structures are found near the location of the metallic deposits?
Write trenches, faults or volcanoes in column 4 of Table 1.
Q4. Write a statement to connect the presence of metallic deposits with trenches or
volcanic areas.
Q5. Why do you think are metallic deposits abundant in places where there are
trenches or volcanoes?
4.
Look for your province in the map.
Q6. Are there metallic deposits in your area?
Q7. What could be reason for the presence or absence of metallic deposits in your
area? You can download the detailed map of Trenches, Faults and volcanoes
in the Philippines from the website of Phivolcs.
Q8. If there are metallic deposits, what activities tell you that there are indeed
deposits in or near your area/province?
The important metallic minerals found in various parts of the Philippines
include gold, copper, iron, chromite (made up of chromium, iron, and other metals),
nickel, cobalt, and platinum. The most productive copper and gold producers in the
Philippines are found in Baguio, the province of Benguet, and in Surigao-Davao
areas. Major producers of nickel are in Palawan and Surigao (DENR Website, 2012).
Metals are important. The properties of metals make them useful for specific
purposes. You learned these in Quarter 1. Iron is the main material for steel bars
used in buildings and road construction. Copper is used in making electrical wires.
Tin is the material for milk cans and other preserved food products. Nickel is mixed
with copper or other metals to form stainless cooking wares. Gold is important in
making jewelry.
What other metals are you familiar with? What are the uses of aluminum?
What metal is used to make GI sheets for roofing? What metals are used to make
artificial arms or legs? Are metals used in chairs and other furniture? Do you know
that some dentists use gold for filling teeth cavities? Look around and find how
versatile metals are.
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The Philippines has also varied nonmetallic resources including sand and
gravel, limestone, marble, clay, and other quarry materials. Your teacher will show
you a map of the nonmetallic deposits in the Philippines. Locate your area and
determine what nonmetallic deposits are found there. How are these deposits
recovered? How are they used in your community? For example: What are the uses
of sand, gravel, or clay? How are marble stones used? Think of other nonmetals and
their uses!
Copper – iron ore
Iron filings
Quartz
Copper ore
Figure 12. From the drawing, what are ores? Have you noticed that a piece of ore
can have more than one kind of mineral in it?
Do you know that the Philippines is listed as the 5th mineral country in the
world, 3rd in gold reserves, 4th in copper, and 5th in nickel! The ores (mineralbearing rocks) are processed out of the country to recover the pure metal. We buy
the pure metal. Is this practice advantageous to the Philippines? Why or why not?
The richness of the Philippines
in terms of mineral resources is being
attributed to its location in the so-called
Pacific Ring of Fire. See Figure 13.
This area is associated with over 450
volcanoes (small triangles in the map)
and is home to approximately 75% of
the world's active volcanoes. Why are
there minerals where there are
volcanoes?
Geologists (scientists who study Figure 13. Besides the Philippines, what
the Earth and the processes that occur other countries are in the Ring of Fire?
in and on it) explain that there is a Do you think they are also rich in mineral
continuous source of heat deep under resources?
the Earth; this melts rocks and other
materials (link to usgs website).The mixture of molten or semi-molten materials is
called magma. Because magma is hotter and lighter than the surrounding rocks, it
rises, melting some of the rocks it passes on the way. If the magma finds a way to
the surface, it will erupt as lava. Lava flow is observed in erupting volcanoes.
But the rising magma does not always reach the surface to erupt. Instead, it
may slowly cool and harden beneath the volcano and form different kinds of igneous
rocks. Under favorable temperature and pressure conditions, the metal-containing
rocks continuously melt and redeposit, eventually forming rich-mineral veins.
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Though originally scattered in very small amounts in magma, the metals are
concentrated when magma convectively moves and circulates ore-bearing liquids
and gases. This is the reason why metallic minerals deposits such as copper, gold,
silver, lead, and zinc are associated with magmas found deep within the roots of
extinct volcanoes. And as you saw in the maps, volcanoes are always near trenches
and faults! You will learn more of this later.
For now you must have realized that the presence of mineral deposits in the
Philippines is not by accident. It is nature’s gift. If before, your association with
volcanoes and trenches is danger and risk to life and property, now you know that
the presence of volcanoes, trenches and other geological structures is the reason for
the rich mineral deposits in the country.
The existence of volcanoes also explains why the Philippines is rich in
geothermal energy (heat from the Earth). Energy resources will be discussed in the
next section.
Energy Resources
The abundance of some metal resources in the Philippines is related to
geologic structures, specifically the presence of volcanoes and trenches in the
country. The year-round warm temperature and availability of water are effects of our
geographic location.
The tropical climate and the geological conditions also provide several
possibilities to get clean and cheap energy. Do you know which energy resources
are due to these factors? Were the following included in your list- solar energy, heat
from the ground (geothermal energy), hydrothermal energy from falling water), wind
energy, and natural gas?
Solar
energy
is
free
and
inexhaustible. This energy source will be
discussed in a later science subject.
Geothermal energy was briefly
introduced in the lesson on mineral
resources and their location.
The
Philippines ranked second to the United
States in terms of geothermal energy
deposits. Geothermal power plants are
located in Banahaw-Makiling, Laguna, Tiwi
in Albay, Bacman in Sorsogon, Palimpinon
in Negros Occidental, Tongonan in Leyte,
and Mt. Apo side of Cotabato.
http://commons.wikimedia.org/wiki/File:Hot_Spring.jpg
Figure 14. Do you know that heat
from the Earth may escape as steam
in a hot spring?
Try to locate places with geothermal power plants in your map? Does your
area have geothermal energy deposits? How do you know?
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Hydrothermal or hydroelectric
power plants use water to generate
electricity. They provide for 27% of total
electricity production in the country.
Ambuklao in Benguet, Mt Province,
Agus in Lanao del Sur and Agus in
Lanao del Norte are large hydrothermal
power plants. Small hydroelectric power
plants are in Caliraya, Laguna, Magat in
Isabela, Loboc in Bohol, and other
places. Used water from hydropower
plants flows through irrigation systems.
Many of the reservoir areas are used
for sport activities.
Photograph courtesy of National Power Corporation,
retrieved from http://www.industcards.com/hydrophilippines.htm
Figure 15. How is water used to
generate electricity?
Again, locate places with hydroelectric power plants in your map? Does your
area have hydroelectric power plants? What other uses do you have for water in
these areas?
Natural gas is a form of fossil fuel, so are coal and crude oil (sometimes
called petroleum). Fossil fuels were formed from plants and animals that lived on
Earth millions of years ago. They are buried deep in the Earth. Natural gas and oil
are taken from the deep through oil rigs while coal is extracted through mining. Fossil
fuels are used to produce electricity and run vehicles and factory machines. Did you
know that petroleum is the raw material for making plastics?
In the Philippines, we have
coal and natural gas deposits.
Coal is a black or brownish black,
solid rock that can be burned. It
contains
about
40%
noncombustible components, thus a
source of air pollution when used
as fuel. Coal deposits are
scattered over the Philippines but
the largest deposit is located in
Semirara Island, Antique. Coal
mines are also located in Cebu,
Zamboanga Sibuguey, Albay,
Surigao, and Negros Provinces.
Figure 16. The black bands in the picture are
coal deposits. Coal is not like the charcoal
you use for broiling fish or barbecue. What do
you think is the difference?
Our natural gas deposits
are found offshore of Palawan. Do
you know where this place is?
The Malampaya Deepwater Gas-to-Power Project employs ‘state-of-the-art
deepwater technology’ to draw natural gas from deep beneath Philippine waters. The
gas fuels three natural gas-fired power stations to provide 40-45% of Luzon's power
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generation requirements. The Department of Energy reports that since October
2001, the Philippines has been importing less petroleum for electricity generation,
providing the country foreign-exchange savings and energy security from this clean
fuel.
Natural gas is considered clean fuel because when burned, it produces the
least carbon dioxide, among fossil fuels. CO 2 is naturally present in air in small
amounts. However, studies show that increase in carbon dioxide in the atmosphere
results in increase in atmospheric temperature, globally. You will learn about global
warming in the next module.
Did you know that in Ilocos Province, giant wind mills as shown in Figure 5 of
this module are used to generate electricity? In Quirino, Ilocos Sur the electricity
generated from wind mills runs a motorized sugarcane press for the community's
muscovado sugar production? This project is a joint effort between the local farmers
and local organizations with support from Japan. In Bangui, Ilocos Norte, the
windmills as high as 50 meters not only help improve the tourism in Ilocos but it also
provides 40% of the energy requirements for electricity in the entire province. This
proves that we do not have to be dependent on fossil fuel in our country.
What do you think are the environmental conditions in Ilocos Sur and Ilocos
Norte that allow them to use wind power for electricity? Do you think there are
places that have these conditions? Support your answers.
Conserving and Protecting Natural Resources
There are two types of natural resources on Earth - renewable and
nonrenewable. What is the difference between these two kinds of resources?
The food people eat comes from plants and animals. Plants are replaced by
new ones after each harvest. People also eat animals. Animals have the capacity to
reproduce and are replaced when young animals are born. Water in a river or in a
well may dry up. But when the rain comes the water is replaced. Plants, animals, and
water are resources that can be replaced. They are renewable resources.
Most plants grow in top soil. Rain and floods wash away top soil. Can top soil
be replaced easily? Soil comes from rocks and materials from dead plants and
animals. It takes thousands of years for soil to form. Soil cannot be replaced easily,
or it takes a very long time to replace. It is a nonrenewable resource.
Metals like copper, iron, and aluminum are abundant on Earth. But people
are using them up fast. They have to dig deeper into the ground to get what they
need. Coal, oil and natural gas (fossil fuels) were formed from plants and animals
that lived on Earth millions of years ago. It takes millions of years for dead plants and
animals to turn into fossil fuels. Soil, coal, oil and natural gas are nonrenewable
resources.
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Before you do Activity 6, think of these sentences: “Too much is taken from
Earth!" and "Too much is put into Earth." You may write up a short essay about your
understanding of the sentences.
Activity 6
How do people destroy natural resources?
Objectives
1.
2.
Identify the effects of some human activities on natural resources.
Suggest ways to reduce the effects.
What to Do
1.
Study Table 2 and tell if you have observed the activities listed in your locality.
Table 2. Ways People Destroy Natural Resources
Activities
Effects on Natural Resources
(1)
(2)
When roads are built, mountains are
blown off using dynamite.
Rice fields are turned into residential or
commercial centers.
People cut too many trees for lumber or
paper or building houses.
More factories are being built to keep up
with the demands of a fast growing
population and industrialization.
Too much mining and quarrying for the
purpose of getting precious metals and
stones and gravel.
Some farmers use too much chemical
fertilizers to replenish soil fertility.
Damage natural habitats and/or kill
plants and animals.
Too much fertilizer destroys the quality
of the soil and is harmful to both human
and animals.
Plastics and other garbage are burned.
Cars, trucks, and tricycles that emit dark
smoke (smoke belchers) are allowed to
travel.
Other activities
2.
Discuss the effects of these activities on natural resources.
3.
Write the effects on the column opposite the activities. An activity may have
more than one effect. Some of the effects have already been listed in the table.
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4.
Do you know of other activities that destroy or cause the depletion of natural
resources? Add them to the list and fill the corresponding effect in column 2.
5.
What can you do to conserve resources?
Protecting Resources in Your Own Way
All resources used by humans, including fuels, metals, and building materials,
come from the Earth. Many of these resources are not in endless supply. It has taken
many thousands and millions of years to develop and accumulate these resources.
To conserve natural resources is to protect or use them wisely without
wasting them or using them up completely. Conserving natural resources can make
them last and be available for future generations. This is what sustainability of
natural resources means. Each one of us should think about how to make things
sustainable. Remember: The lives of future generations depend on how we use
natural resources today.
Activity 7
Are you ready for “Make-a-Difference” Day?
This activity involves you in hands-on activities that help you learn more
about reducing waste, reusing materials instead of throwing them away, recycling,
composting, and conserving natural resources and energy. There are many activities
that you can include: conducting a "waste-free lunch" or building art materials out of
cans, bottles, and other recyclable trash. Depending on the location and nature of
your school, you might want to include river cleanup, trail maintenance, or tree
planting. Or, you can mix these activities with a poster making contest for use in the
campaign on non-use of plastic bags for shopping and/or marketing.
What to do
1.
In your group, make a list of what is done in your school that help conserve
natural resources. Discuss your list before finalizing the report.
2.
Make another list of what is done in your school that do not help conserve
natural resources. For example, do you still have lots of things in the trash can
or on the ground? What are they? What is being done with them?
3.
Come up with a one-day plan on what else can be done in school to conserve
natural resources. Present your plan to the class.
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4.
Based on the group presentation, decide which part in the plans will be
adopted or adapted to make a class plan. The plan should consider the
following:
 Easy to follow
 Who will be responsible for making the plan happen
 What should be done if the people responsible for making the plan happen
will not or cannot do it
 What natural resources will be conserved
 Schedule of activities to include monitoring
 Why you think this plan is the best idea
5.
With your teacher’s permission, make an appointment with your principal to
present your plan and to solicit support. Maybe she might recommend the
“Make-a-Difference” Day for the whole school!
Hopefully, the “Make-a-Difference” Day will engage you in a variety of
environmental activities that help foster not only an appreciation for the environment
and the resources it provides but also develop a life-long environmental stewardship
among your age group.
Links and Other Reading Materials
gdis.denr.gov.ph (Geohazard Map)
http://www.phivolcs.dost.gov.ph
http://www.jcmiras.net/surge/p124.htm (Geothermal power plants in the Philippines)
http://www.industcards.com/hydro-philippines.htm (Hydroelectric power plants in
the Philippines)
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Suggested time allotment: 12 hours
Unit 4
MODULE
2
SOLAR ENERGY
AND THE ATMOSPHERE
In the previous module, you learned that the presence of different natural
resources in the Philippines is related to the country’s location. It was also mentioned
that the climate in a certain area depends on its latitude. In this module, you are
going to learn more about how the location of the Philippines influences its climate
and weather. To prepare you for this lesson, you must first learn about the envelope
of air that surrounds the Earth where all weather events happen – the atmosphere.
Activity 1
What is the basis for
dividing Earth’s
atmosphere into
layers?
Earth’s atmosphere is divided
into five layers. What is the basis for
subdividing the atmosphere?
Objectives
You will be able to gather
information about Earth’s atmosphere
based on a graph. Specifically, you will:
1.
2.
3.
describe the features of each of
the five layers;
compare the features of the five
layers; and
explain the basis for the division
of the layers of the atmosphere.
Figure 1. What are the layers of the
atmosphere?
233
What to use


Graph in Figure 1
A ruler, if available
What to do
1.
Study the graph.
Q1.
Q2.
Q3.
Q4.
Q5.
What are the five layers? Estimate the height of each layer.
Describe the graph for each layer.
In which layer is temperature increasing with increasing altitude?
In which layer is temperature decreasing with increasing altitude?
What is the relationship between temperature and height in the
- troposphere?
- stratosphere?
- mesosphere?
- thermosphere?
- exosphere?
Q6. Observe the whole graph. What is the basis for the division of Earth’s
atmosphere?
Q7. From the graph, can you generalize that the higher the layer of the atmosphere
(that is closer to the Sun), the hotter the temperature? Why or why not?
Q8. What other information about Earth’s atmosphere can you derive from the
graph?
2.
Read the succeeding paragraphs and think of a way to organize and
summarize the data about the atmosphere from the graph and the information
in the discussion that follows.
The troposphere is the layer closest to Earth’s surface. The temperature just
above the ground is hotter than the temperature high above. Weather occurs in the
troposphere because this layer contains most of the water vapor. Remember the
water cycle? Without water, there would be no clouds, rain, snow or other weather
features. Air in the troposphere is constantly moving. As a result, aircraft flying
through the troposphere may have a very bumpy ride – what we know as turbulence.
People who have used the airplane for travelling have experienced this especially
when there is a typhoon in areas where the plane passes through.
The stratosphere is the layer of air that extends to about 50 km from Earth’s
surface. Many jet aircraft fly in the stratosphere because it is very stable. It is in the
stratosphere that we find the ozone layer. The ozone layer absorbs much of the
Sun’s harmful radiation that would otherwise be dangerous to plant and animal life.
The layer between 50 km and 80 km above the Earth’s surface is called the
mesosphere. Air in this layer is very thin and cold. Meteors or rock fragments burn up
in the mesosphere.
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The thermosphere is between 80 km and 110 km above the Earth. Space
shuttles fly in this area and it is also where the auroras are found. Auroras are
caused when the solar wind strikes gases in the atmosphere above the Poles. Why
can we not see auroras in the Philippines?
The upper limit of our atmosphere is the exosphere. This layer of the
atmosphere merges into space. Satellites are stationed in this area, 500 km to 1000
km from Earth.
To summarize what has been discussed: More than three quarters of Earth’s
atmosphere is made up of nitrogen while one fifth is oxygen. The remaining 1% is a
mixture of carbon dioxide, water vapor, and ozone. These gases not only produce
important weather features such as cloud and rain, but also have considerable
influence on the overall climate of the Earth, through the greenhouse effect and
global warming.
What is the Greenhouse Effect?
In order to understand the greenhouse effect, you need to first understand
how a real greenhouse works.
In temperate countries, a greenhouse is used to grow seedlings in the late
winter and early spring and later, planted in the open field when the weather is
warmer. Greenhouses also protect plants from weather phenomena such snowstorm
or dust storms. In tropical countries, greenhouses are used by commercial plant
growers to protect flowering and ornamental plants from harsh weather conditions
and insect attack.
Greenhouses range in size from small sheds to very large buildings. They
also vary in terms of types of covering materials. Some are made of glass while
others are made of plastic.
Activity 2
Does a greenhouse retain or release heat?
Objectives
The activity will enable you to
1.
2.
3.
construct a model greenhouse.
find out if your model greenhouse retains heat
relate the concept of greenhouse to the increasing temperature of
Earth’s atmosphere.
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What to use






2-liter plastic soft drink bottle
2-plastic containers
to serve as base of
the bottles
CAUTION
knife or scissors
transparent tape
two alcohol
thermometers
one reading lamp (if
available), otherwise
bring the setups under the
Sun
Be careful when
handling sharp objects
like knife or scissors
and breakable
equipment like
thermometer.
What to do
Constructing the model greenhouse
For each model greenhouse you will need a two-liter plastic soft drink
container (with cap) and a shallow plastic container for the base.
1.
Remove the label of the soft drink bottle but keep the cap attached.
2.
Cut off carefully, the end of the bottle approximately 5-6 cm from the bottom.
Dispose of the bottom piece.
3.
Place the bottle with cap in the plastic base. This is your model greenhouse.
Label it Bottle A.
4.
Use scissors or knife to cut several elongated openings or vents (1.5 x 5.0 cm)
on the sides of Bottle B. Leave Bottle A intact.
5.
Tape a thermometer onto a piece of cardboard. Make sure that the cardboard
is longer than the thermometer so that the bulb will not touch the plastic base.
Make two thermometer setups, one for Bottle A and another for Bottle B. Place
one thermometer setup in each bottle.
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Figure 2. How to construct a model greenhouse
6.
7.
Place both bottles approximately 10 cm away
from the lamp. DO NOT turn on the lamp yet.
Q1.
Predict which bottle will get hotter when
you turn on the light or when they are
exposed to the Sun. How will you know
that one bottle is hotter than the other?
Q2.
Write down your prediction and the reason
why you predicted that way.
Turn on the light and begin collecting data every
five minutes for 25 minutes. (Note: But if you have
no lamp, place the setups under the Sun. Read
the temperature every 20 minutes for over two
hours.)
NOTE:
If you have no lamp,
bring the setups
outside the classroom
under the Sun where
they will not be
disturbed.
8.
Record the temperature readings of Bottle A and Bottle B in your notebook.
9.
Q3.
Q4.
Q5.
Q6.
Q7.
Q8.
Q9.
Graph your data separately for Bottles A and B.
What variable did you put in the x-axis? In the y-axis?
Why did you put these data in the x and y axes, respectively?
Describe the graph resulting from observations in Bottle A.
Describe the graph resulting from observations in Bottle B.
Explain the similarities in the graphs of Bottles A and B.
Explain the differences in the graphs of Bottles A and B.
Does this activity help you answer the question in the activity title: Do
greenhouses retain heat? What is the evidence?
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Greenhouses allow sunlight to enter but prevent heat from escaping. The
transparent covering of the greenhouse allows visible light to enter without
obstruction. It warms the inside of the greenhouse as energy is absorbed by the
plants, soil, and other things inside the building. Air warmed by the heat inside is
retained in the building by the roof and wall. The transparent covering also prevents
the heat from leaving by reflecting the energy back into the walls and preventing
outside winds from carrying it away.
The Earth’s atmosphere is compared to a greenhouse. You know that
besides nitrogen and oxygen, Earth’s atmosphere contains trace gases such as
carbon dioxide, water vapor, methane, and ozone. Like the glass in a greenhouse,
the trace gases have a similar effect on the Sun’s rays. They allow sunlight to pass
through, resulting in the warming up of the Earth’s surface. But they absorb the
energy coming from the Earth’s surface, keeping the Earth’s temperature suitable for
life on Earth. The process by which the Earth’s atmosphere warms up is called
‘greenhouse effect,’ and the trace gases are referred to as ‘greenhouse gases.’
https://sites.google.com/site/glowar88/all-about-global-warming/1-what-is-global-warming
Figure 3. Why are greenhouse gases like the glass
in the greenhouse?
The ‘greenhouse effect’ is a natural process and it warms the Earth. Without
the greenhouse effect, Earth would be very cold, too cold for living things, such as
plants and animals.
To further understand the effect of greenhouse gases look at Figure 4. It
contains some data about Venus and Earth, planets that are almost of the same size
and if you remember from elementary school science, are near each other, so they
are called twin planets. The composition of atmosphere and the average surface
238
temperature of the two planets are also given. Why is the average temperature of
Venus very much higher than that of Earth? What could have caused this
phenomenon?
Both Earth and Venus
have
carbon
dioxide,
a
greenhouse
gas,
in
their
atmospheres. The small amount
of carbon dioxide on Earth’s gives
the right temperature for living
things to survive. With the high
surface temperature of Venus due
to its high carbon dioxide
concentration, do you think life
forms like those we know of could
exist there? Why or why not?
Figure 4. What gas is present in the
atmosphere of Venus that explains its high
surface temperature?
Is Earth Getting Warmer? What is the Evidence?
Studies have shown that before 1750 (called the pre-industrialization years), carbon
dioxide concentration was about 0.028 percent or 280 parts per million (ppm) by
volume. The graph below shows the concentration of carbon dioxide from 1958 to
2003. What information can you derive from the graph?
Recent studies report that
in 2000-2009, carbon dioxide rose
by 2.0 ppm per year. In 2011, the
level is higher than at any time
during the last 800 thousand
years.
Local
temperatures
fluctuate naturally, over the past
50 years but the average global
temperature has increased at the
fastest rate in recorded history.
So what if there is
increasing emission of greenhouse
gases like carbon dioxide into the
atmosphere? What is the problem
with a small increase in carbon
dioxide concentration in the
atmosphere?
http://en.wikipedia.org/wiki/File:Mauna_Loa_Carbon_Dio
xide-en.svg#file
Figure 5. Carbon dioxide measurements in
Mauna Loa Observatory, Hawaii
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More carbon dioxide means that more heat is trapped in Earth’s atmosphere.
More heat cannot return back into space. More heat trapped by the carbon dioxide
means a warmer Earth.
The increasing temperature phenomenon is known as ‘global warming’.
Global means that all countries and people around the world are affected even if that
country is not a major contributor of greenhouse gases. Many scientists now agree
that many human activities emit more greenhouses gases into the atmosphere,
making the natural greenhouse effect stronger. Scientists are also saying that if we
carry on polluting the atmosphere with greenhouse gases, it will have a dangerous
effect on the Earth.
Sources of Greenhouse Gases
Carbon dioxide is naturally produced when people and animals breathe.
Plants and trees take in and use carbon dioxide to produce their own food.
Volcanoes also produce carbon dioxide. Methane comes from grazing animals as
they digest their food and from decaying matter in wet rice fields. Ozone is also
naturally present in the stratosphere.
But human activities emit a lot of greenhouse gases into the atmosphere.
Study Figure 7.
http://en.wikipedia.org/wiki/File:Global_Carbon_Emission_by_Type
.png
Figure 6. Does burning of fossil fuels raise the carbon
dioxide concentration in the atmosphere?
Which fossil fuel has the highest contribution to carbon dioxide concentration
in the atmosphere?
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What human activities use this fuel? List at least three.
Recall Module 1. What kind of fossil fuels are used in the Philippines?
Are we also contributing to the increase in carbon dioxide concentration in the
atmosphere? Why or why not?
Carbon dioxide comes from the burning of fossil fuel such as coal, crude oil and
natural gas. Cutting down and burning of trees releases carbon dioxide. Methane
can also be released from buried waste. For example, the left-over food, garden
wastes, and animal wastes collected from our homes are thrown into dumpsites.
When lots of wastes are compressed and packed together, they produce methane.
Coal mining also produces methane.
Another group of greenhouse gases includes the chlorofluorocarbons or
CFCs for short. CFCs have been used in spray cans as propellants, in refrigerators
as refrigerants, and in making foam plastics as foaming agents. They become
dangerous when released into the atmosphere, depleting the ozone layer. For this
reason, their use has been banned around the world.
What have you learned about the atmosphere? There are natural processes
in the atmosphere that protect and sustain life on Earth. For example, the
greenhouse effect keeps temperature on Earth just right for living things. For as long
as the concentration of greenhouse gases are controlled, we will have no problem.
But human beings activities have emitted greenhouse gases into the
atmosphere, increasing their levels to quantities that have adverse effects on people,
plants, animals and the physical environment. Burning of fossil fuels, for example,
has increased levels of carbon dioxide thus trapping more heat, increasing air
temperature, and causing global warming. Such global phenomenon is feared to melt
polar ice caps and cause flooding to low-lying areas that will result to reduction in
biodiversity. It is even feared that global warming is already changing climates
around the globe, causing stronger typhoons, and creating many health-related
problems. You will learn more about climate change later.
Common Atmospheric Phenomena
In the next section, you will learn two concepts that will help you understand
common atmospheric phenomena: why the wind blows, why monsoons occur, and
what is the so-called intertropical convergence zone. All of these are driven by the
same thing: the heat of the Sun or solar energy. Thus, we begin by asking, what
happens when air is heated?
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Activity 3
What happens when air is heated?
Objective
After this activity, you should be able to explain what happens when air is
heated.
What to use
two paper bags
candle
long straight stick
match
masking tape
chair
Figure 7. Setup for Activity 3
What to do
1.
Attach a paper bag to each end of the stick (see drawing above). The open end
of each bag should be facing down.
2.
Balance the stick with the paper bags on the chair (see drawing below.)
3.
Make a prediction: what do
you think will happen if you
place a lighted candle under
the open end of one of the
bags?
4.
Now, light the candle and
place it below one of the bags.
Caution: Do not place the
candle too close to the paper
bag. It may catch fire. Be
ready with a pail of water or
wet rag just in case.
Figure 8. Balance the stick with paper bags on
a chair.
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Q1. Was your prediction accurate?
Describe what happened.
Q2. Can you explain why?
Figure 9. What will happen when a lighted
candle is placed under one of the bags?
This is the first concept that you need to know: Warm air rises. Now, try to
answer the following question. When warm air is rising, what is its effect on the air in
the surroundings? Will the air in the surroundings stay in place? Or will it be affected
in some way by the rising air? Do the following activity and find out.
Activity 4
What happens to the air in the surroundings as
warm air rises?
Objective
After performing this activity, you should be able to
explain what happens to the air in the surroundings as
warm air rises.
What to use
box
scissors
cardboard tube
clear plastic
candle
match
smoke source
(ex. mosquito coil)
Figure 10.
Setup for Activity 4
What to do
Pre-activity
Make two holes in the box: one hole on one side and another hole on top (see
drawing). Place the cardboard tube over the hole on top and tape it in place. Make a
window at the front side of the box so you can see inside. Cover the window with
clear plastic to make the box airtight.
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Activity proper
1.
Open the box and place the candle directly below the hole on top. Light up the
candle and close the box.
2.
Make a prediction: What do you think will happen if you place a smoke source
near the hole?
3.
Now, place the smoke source near the
hole.
Q1. Was your prediction accurate?
Q2. What happened?
Q3. Can you explain why?
Figure 11. What happens to the
smoke when the source is placed
near the hole?
What Makes the Air Move?
As you have seen in the activity, air in the surroundings can be affected by
rising warm air. The drawing below shows how this happens. First, the air above the
candle becomes warm because of the flame. What happens to this warm air? It
rises. As warm air rises, what happens to the air in the surroundings? It will move
toward the place where warm air is rising. But you cannot see air, how can you tell
that it is moving? Did you see smoke from the mosquito coil? The movement of the
smoke shows the movement of the air.
Figure 12. Air in the surroundings move
toward the place where warm air is
rising.
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Let us now relate what happened in the activity to what happens in nature.
During the day, the surface of the Earth becomes warm because of the Sun. Some
parts of the Earth will warm up more quickly than others. Naturally, the air above the
warmer surfaces will also become warm. What happens to the warm air? Just like in
the activity, it will rise. How is the air in the surroundings affected? It will move toward
the place where warm air is rising. This is the other concept that you need to know:
Air moves toward the place where warm air is rising.
Whenever we feel the air moving, that means that somewhere, warm air is
rising. And the air around us moves toward the place where warm air is rising. Do
you remember that ‘moving air’ is called wind? Every time you feel the wind, it means
that air is moving toward the place where warm air is rising. Strictly speaking, wind is
air that is moving horizontally.
Let us use now the two concepts you have learned to explain other things.
You know that the surface of the Earth is made basically of two things: land and
water. When the Sun’s rays strike land and water, do they heat up as fast as each
other? Do land and water absorb heat from the Sun in the same way? Or is there a
difference? Perform the next activity and find out.
Activity 5
Which warms up faster?
Objectives
After performing this activity, you should be able to
1.
2.
3.
compare which warms up faster: sand or water
compare which cools faster: sand or water
use the results of the activity to explain sea breeze and land breeze
What to use
2 identical plastic containers
2 thermometers
2 iron stands with clamps
string
water
sand
What to do
1.
In the shade, set up everything as shown below. The bulbs of the thermometer
should be 2 cm below the surface of the water and sand.
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Figure 13. Setup for Activity 5
2.
Wait for 5 minutes, then read the initial temperature of the water and sand.
Record the temperature readings below.
Initial temperature reading for water: __________
Initial temperature reading for sand: __________
3.
Now, place the setup under the Sun. Read the thermometers again and record
the temperature readings in Table 1. Read every 5 minutes for 25 minutes.
Table 1. In the Sun
Observation
time (minutes)
0
5
10
15
20
25
4.
Water
Sand
After 25 minutes, bring the setup back to the shade. Read the thermometers
and record the temperature readings in Table 2. Read every 5 minutes for 25
minutes.
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Table 2. In the shade
Observation
time (minutes)
0
5
10
15
20
25
5.
Water
Sand
Study the data in the tables and answer the following questions.
Q1. Which has a higher temperature after 25 minutes in the Sun, water or sand?
Q2. After 25 minutes, how many Celsius degrees was the increase in the
temperature of the water? Of the sand?
6.
Make a line graph using the temperature readings taken while the setup was in
the Sun.
Q3. Based on the graph, which became hot faster, water or sand?
Q4. What happened to the temperature of the water and sand when brought to the
shade?
Q5. How many Celsius degrees was the decrease in temperature of the water after
25 minutes? Of the sand?
7.
Make a line graph using the temperature readings taken when the setup was in
the shade.
Q6. Based on the graph, which cooled down faster, water or sand?
Sea Breeze and Land Breeze
The sand and water in the previous activity stand for land and water in real
life. From the activity, you have learned that sand heats up faster than water, and
that sand cools down faster than water. In the same way, when land surfaces are
exposed to the Sun during the day, they heat up faster than bodies of water. At night,
when the Sun has set, the land loses heat faster than bodies of water. How does this
affect the air in the surroundings?
Imagine that you are standing by the sea, along the shore. During the day,
the land heats up faster than the water in the sea. The air above land will then
become warm ahead of the air above the sea. You know what happens to warm air:
it rises. So the warmer air above the land will rise. The air above the sea will then
move in to replace the rising warm air. (See drawing below.) You will then feel this
moving air as a light wind—a sea breeze.
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Figure 14. When does sea breeze occur?
What will happen at night, when the Sun is gone? The land and sea will both
cool down. But the land will lose heat faster than the water in the sea. In other words,
the sea will stay warm longer. This time the air above the sea will be warmer than
that above land. The warm air above the sea will then rise. Air from land will move
out to replace the rising warm air. (See drawing below.) This moving air or wind from
land is called a land breeze.
Figure 15. When does land breeze occur?
In the illustration above, you can see an arrow pointing upward. This
represents rising warm air. The place where warm air rises is a place where air
pressure is low. In other words, the place where warm air is rising is a low-pressure
area. In contrast, cold air is dense and tends to sink. The place where cold air is
sinking is a high-pressure area. Based on what you learned so far, in what direction
does air move, from a low-pressure area to a high-pressure area or the other way
around? You probably know the answer already. But the next section will make it
clearer for you.
Monsoons
Do you know what monsoons are? Many people think that monsoons are
rains. They are not. Monsoons are wind systems. But these winds usually bring
abundant rainfall to the country and this is probably the reason why they have been
mistaken for rains. In Filipino, the monsoons are called amihan or habagat,
depending on where the winds come from. Find out which is which in the following
activity.
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Activity 6
In what direction do winds blow–from high to low
pressure area or vice versa?
Objectives
After performing this activity, you should be able to
1.
2.
3.
4.
Interpret a map to determine direction of wind movement
Explain why it is cold around in December to February and warm around
July.
Illustrate why habagat brings lots of rain
Give examples how the monsoons (amihan and habagat) affect people.
What to use
Figure 16: Pressure and Winds in January
Figure 17: Pressure and Winds in July
pencil
What to do
Part I.
Study Figure 16. It shows the air pressure and direction of winds in different parts of
the world in January. Low-pressure areas are marked by L and high-pressure areas
are marked by H. Broken lines with arrowheads show the direction of the wind.
Q1. Choose a low-pressure area and study the direction of the winds around it. Do
the winds move toward the low-pressure area or away from it?
Q2. Choose a high-pressure area and study the direction of the winds around it. Do
the winds move toward the high-pressure area or away from it?
Q3. In what direction do winds blow? Do winds blow from high-pressure areas to
low-pressure areas? Or, from low-pressure areas to high-pressure areas?
Q4. Where is North in the map? South? West? East? Write the directions on the
map.
Q5. Where is the Philippines on the map? Encircle it.
Q6. Study the wind direction near the Philippine area. From what direction does the
wind blow near the Philippines in January?
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250
Figure 16. Pressure and Winds in January
251
Figure 17. Pressure and Winds in July
Part II.
Study Figure 18. It shows the air pressure and direction of winds in different parts of
the world in July.
Q7.
Study the wind direction near the Philippine area. From what direction does
the wind blow in the vicinity of the Philippines in July?
Figure 16 shows what happens during the colder months. The wind blows
from the high-pressure area in the Asian continent toward the low-pressure area
south of the Philippines. The cold air that we experience from December to February
is part of this wind system. This monsoon wind is locally known as amihan. As you
can see from Figure 16, the wind passes over some bodies of water before it
reaches the Philippines. The wind picks up moisture along the way and brings rain to
the eastern part of the Philippines.
Now, what happens during the warmer months? Study Figure 17 carefully.
What do you observe about the low-pressure area and high-pressure area near the
Philippines? They have changed places. (You will learn why in the next module.) As
a result, the direction of the wind also changes. This time the wind will move from the
high-pressure area in Australia to the low-pressure area in the Asian continent. This
monsoon wind is locally called habagat. Trace the path of the habagat before it
reaches the Philippines. Can you explain why the habagat brings so much rain?
Which part of the Philippines does the habagat affect the most?
The monsoons, habagat and amihan, affect people in different ways. Try to
explain the following. Why do farmers welcome the monsoons? Why are fisherfolk
not so happy about the monsoons? Why do energy providers appreciate the
monsoons? Why are fishpen owners worried about the monsoons? How do the
monsoons affect your own town?
In the next section, you will apply the two concepts once more to explain
another weather event.
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The Intertropical Convergence Zone (ITCZ)
Many people who listen to weather forecasts are confused about the
intertropical convergence zone. But it is easy to understand it once you know that
warm air rises, and air moves toward the place where warm air is rising. Take a look
at the drawing below.
Figure 18. Sun’s rays at the equator and
at a higher latitude
Figure 18 shows the rays of the Sun at two different places at noon. Study
the drawing carefully. Where would you observe the Sun directly above you? When
you are at the equator? Or when you are at a higher latitude?
As you can see, the position of the Sun at midday depends on where you are.
At the equator, the Sun will be directly overhead and the rays of the Sun will hit the
ground directly. At a higher latitude, the Sun will be lower in the sky and the Sun’s
rays will strike the ground at a lower angle. Where do you think will it be warmer?
It is clear that it is warmer at the equator than anywhere else. Because of
that, the air over the equator will be warmer than the air over other parts of the Earth.
And you already know what happens to warm air. It rises. And when warm air rises,
air in the surroundings will then move as a result.
Figure 19. How does the air move at the equator?
253
As you can see from Figure 19, air from north of the equator and air from
south of the equator will move toward the place where warm air is rising. Thus, the
intertropical convergence zone is the place where winds in the tropics meet or
converge. (Recall that the area near the equator is called the tropics.) In time the
rising warm air will form clouds, which may lead to thunderstorms. Now you know
why weather forecasters often blame the ITCZ for some heavy afternoon rains. The
band of white clouds in the following picture shows the location of the ITCZ.
Figure 20. Satellite photo showing the location of ITCZ
Summary
This module discussed global atmospheric phenomena like the greenhouse
effect and global warming (including ozone depletion) that affect people, plants,
animals and the physical environment around the world. And though the greenhouse
effect is a natural phenomenon, there is a growing concern that human activities
have emitted substances into the atmosphere that are causing changes in weather
patterns at the local level.
Highlighted in this module are concepts used to explain common atmospheric
phenomena: why the wind blows, why monsoons occur, and what is the so-called
inter tropical convergence zone.
It is important for everyone to understand the varied atmospheric phenomena
so that we can all prepare for whatever changes that occur in the environment and
cope with these changes.
There are still many things to learn about the atmosphere, specifically on
weather and climate. You have just been provided with the basic concepts. You will
learn more as you move to Grade 8 and onwards.
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Suggested time allotment: 10 hours
Unit 4
MODULE
3
SEASONS AND ECLIPSES
Overview
In Grade 6, you have learned about the major members of our solar system.
Like the other planets, the Earth moves mainly in two ways: it spins on its axis and it
goes around the Sun. And as the Earth revolves around the Sun, the Moon is also
revolving around the Earth. Can you imagine all these “motions” happening at the
same time? The amazing thing is we do not feel that the Earth is moving. In reality,
the planet is speeding around the Sun at 30 kilometers each second. (The solar
system is also moving around the center of the Milky Way!)
But even if we do not actually see the Earth or Moon moving, we can observe
the effects of their motion. For example, because the Earth rotates, we experience
day and night. As the Moon goes around the Earth, we see changes in the Moon‘s
appearance.
In this module you will learn that the motions of the Earth and Moon have
other effects. Read on and find out why.
Seasons
In Grade 6, you tracked the weather for the whole school year. You found out
that there are two seasons in the Philippines: rainy and dry. You might have noticed
too that there are months of the year when it is cold and months when it is hot. The
seasons follow each other regularly and you can tell in advance when it is going to
be warm or cold and when it is going to be rainy or not. But can you explain why
there are seasons at all? Do you know why the seasons change? The following
activity will help you understand why.
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Activity 1
Why do the seasons change?
Objective
After performing this activity, you should be able to give one reason why the
seasons change.
What to use
Figures 1 to 5
What to do
1.
Study Figure 1 carefully. It shows the Earth at different locations along its orbit
around the Sun. Note that the axis of Earth is not perpendicular to its plane of
orbit; it is tilted. The letter “N” refers to the North Pole while “S” refers to the
South Pole.
Figure 1. The drawing shows the location of the Earth at
different times of the year. Note that the axis of Earth is not
vertical; it is tilted. (Not drawn to scale)
Q1. In which month is the North Pole tilted toward the Sun– in June or December?
Q2. In which month is the North Pole tilted away from the Sun– in June or
December?
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2.
Study Figure 2 carefully. The drawing shows how the Earth is oriented with
respect to the Sun during the month of June.
Figure 2. Where do direct rays from the Sun fall in June?
Q3. In June, which hemisphere receives direct rays from the Sun– the Northern
Hemisphere or Southern Hemisphere?
3.
Study Figure 3 carefully. The drawing shows how the Earth is oriented with
respect to the Sun during the month of December.
Figure 3. Where do direct rays from the Sun fall in December?
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Q4. In December, which hemisphere receives direct rays from the Sun- the
Northern Hemisphere or Southern Hemisphere?
Look at Figure 1 again. Note that the axis of the Earth is not perpendicular to
the plane of its orbit; it is tilted from the vertical by 23.5 degrees. What is the effect of
this tilt?
In June, the North Pole is tilted toward the Sun. Naturally, the Northern
Hemisphere will also be tilted toward the Sun. The Northern Hemisphere will then
receive direct rays from the Sun (Fig. 2). When the Sun’s rays hit the ground directly,
the place will become warmer than when the rays are oblique (Figures 4 and 5). This
is why it is summer in the Northern Hemisphere at this time.
But the Earth is not stationary. The Earth goes around the Sun. What
happens when the Earth has moved to the other side of the Sun?
After six months, in December, the North Pole will be pointing away from the
Sun (Figure 1). The Northern Hemisphere will no longer receive direct rays from the
Sun. The Northern Hemisphere will then experience a time of cold. For temperate
countries in the Northern Hemisphere, it will be winter. In tropical Philippines, it is
simply the cold season.
What’s the angle got to do with it?
“Direct rays” means that the rays of
the Sun hit the ground at 90°. The rays
are vertical or perpendicular to the
ground. When the Sun’s rays strike the
ground at a high angle, each square
meter of the ground receives a greater
amount of solar energy than when the
rays are inclined. The result is greater
warming. (See Figure 4.)
On the other hand, when the Sun’s
rays come in at an oblique angle, each
square meter of the ground will receive
a lesser amount of solar energy. That’s
because at lower angles, solar energy
will be distributed over a wider area.
The place will then experience less
heating up. (See Figure 5.)
Figure 4. In the tropics, the warm season is due to the Sun’s rays hitting the ground
directly. To an observer, the position of the Sun at noon will be exactly overhead.
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Which part of the Earth receives the direct rays of the Sun in December? As
you can see in Figure 3, it is the South Pole that is tilted toward the Sun. This time
the Sun’s direct rays will fall on the Southern Hemisphere. It will then be summer in
the Southern Hemisphere. Thus, when it is cold in the Northern Hemisphere, it is
warm in the Southern Hemisphere.
After another six months, in June of the following year, the Earth will have
made one full trip around the Sun. The Sun’s direct rays will fall on the Northern
Hemisphere once more. It will be warm in the Northern Hemisphere and cold in the
Southern Hemisphere all over again. Thus, the seasons change because the direct
rays of the Sun shift from one hemisphere to the other as the Earth goes around the
Sun.
Figure 5. The cold season is the result of the Sun’s rays
striking the ground at a lower angle. To an observer,
the Sun at midday will not be directly above; it will be
lower in the sky.
Now you know one of the reasons why the seasons change. Sometimes the
Sun’s direct rays fall on the Northern Hemisphere and sometimes they fall on the
Southern Hemisphere. And that is because the Earth is tilted and it goes around the
Sun. There is another reason why the seasons change. Find out in the next activity.
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Activity 2
How does the length of daytime and nighttime
affect the season?
Objectives
After performing this activity, you should be able to
1. Interpret data about sunrise and sunset to tell when daytime is long and when
daytime is short;
2. Infer the effect of length of daytime and nighttime on seasons;
3. Summarize the reasons why seasons change based on Activity 1 and Activity
What to use
Table 1
What to do
1.
Study the table below. It shows the times of sunrise and sunset on one day of
each month.
Table 1: Sunrise and sunset in Manila on selected days of 2011
Length of
Day
Sunrise
Sunset
daytime
Jan 22, 2011
6:25 AM
5:50 PM
11h 25m
Feb 22, 2011
6:17 AM
6:02 PM
11h 45m
Mar 22, 2011
5:59 AM
6:07 PM
12h 08m
Apr 22, 2011
5:38 AM
6:11 PM
12h 33m
May 22, 2011
5:27 AM
6:19 PM
12h 52m
Jun 22, 2011
5:28 AM
6:28 PM
13h 00m
Jul 22, 2011
5:36 AM
6:28 PM
12h 52m
Aug 22, 2011
5:43 AM
6:15 PM
12h 32m
Sep 22, 2011
5:45 AM
5:53 PM
12h 08m
Oct 22, 2011
5:49 AM
5:33 PM
11h 44m
Nov 22, 2011
6:00 AM
5:24 PM
11h 24m
Dec 22, 2011
6:16 AM
5:32 PM
11h 16m
Q1. Compare the times of sunrise from January, 2011 to December, 2011. What do
you notice?
Q2. Compare the times of sunset during the same period. What do you notice?
Q3. Compare the time of sunrise on June 22, 2011 with that on December 22,
2011. On which day did the Sun rise earlier?
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Q4. Compare the time of sunset on June 22, 2011 with that on December 22, 2011.
On which day did the Sun set later?
Q5. When was daytime the longest?
Q6. When was daytime the shortest?
You know that there are 24 hours in a day. You probably think that daytime
and nighttime are always equal. But you can infer from the activity that the length of
daytime changes from month to month. When the North Pole is tilted toward the Sun,
daytime will be longer than nighttime in the Northern Hemisphere.
What happens when daytime is longer than nighttime? The time of heating up
during the day will be longer than the time of cooling down at night. The Northern
Hemisphere steadily warms up and the result is summer. At the same time, in the
Southern Hemisphere, the opposite is happening. Nights are longer than daytime. It
is winter there.
But when the Earth has moved farther along its orbit, the North Pole will then
be tilted away from the Sun. Nighttime will then be longer than daytime in the
Northern Hemisphere. There would be a shorter time for heating up and longer time
to cool down. The result is winter in the Northern Hemisphere. In tropical Philippines,
it is the cold season. Meanwhile, it will be summer in the Southern Hemisphere.
At this point, you should now be able to explain why the seasons change.
Your explanation should include the following things: the tilt of the Earth; its
revolution around the Sun; the direct rays of the Sun, and the length of daytime.
There are other factors that affect the seasons but these are the most important.
After discussing the motions of the Earth, let us now focus on the motions of
another celestial object, the Moon. You have seen that the shape of the Moon
appears to change from night to night. You have learned in Grade 5 that the
changing phases of the Moon are due to the revolution of the Moon. The movement
of the Moon also produces other phenomena which you will learn in the next section.
Shadows and Eclipses
Do you know how shadows are formed? How about
eclipses? Do you know why they occur? Do you think that
shadows and eclipses are related in any way?
In this section, you will review what you know about
shadows and later on perform an activity on eclipses.
Afterwards, you will look at some common beliefs about
eclipses and figure out if they have any scientific bases at all.
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Using a shadow-play activity, your teacher will demonstrate how shadows are
formed and how shadows affect the surroundings. The demonstrations should lead
you to the following ideas:



When a light source is blocked by an object, a shadow of that object is
cast. The shadow will darken the object on which it falls.
The distance of the object from the light source affects the size of its
shadow. When an object is closer to the light source, its shadow will
appear big. But when it is farther from the light source, its shadow is
smaller.
The occurrence of shadows is an ordinary phenomenon that you
experience every day. Shadows can be seen anywhere. Sometimes, the
shadow appears bigger than the original object, other times smaller.
How about in outer space? Are shadows formed there, too? How can you tell
when you are here on Earth?
The next activity will help you answer these questions. The materials that you
will use in the activity represent some astronomical objects in space. You will need to
simulate space by making the activity area dark. Cover the windows with dark
materials such as black garbage bag or dark cloth.
Activity 3
Are there shadows in space?
Objective
After performing this activity, you should be able to explain how shadows are
formed in space.
What to use






1 big ball (plastic or Styrofoam ball)
1 small ball (diameter must be about ¼ of the big ball)
flashlight or other light source
2 pieces barbecue stick (about one ruler long)
any white paper or cardboard larger than the big ball
Styrofoam block or block of wood as a base
What to do
Note: All throughout the activity, stay at the back or at the side of the flashlight as
much as possible. None of your members should stay at the back of the big
ball, unless specified.
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1.
Pierce the small ball in the middle with the barbecue stick.
Then push the stick into a Styrofoam block to make it stand
(see drawing on the right). The small ball represents the
Moon. Do the same to the big ball. The big ball represents
the Earth.
2.
Hold the flashlight and shine it on the small ball (see drawing below). The
distance between the flashlight and the ball is one footstep. Observe the small
ball as you shine light on it. The flashlight represents the Sun.
Sun
Moon
1 footstep
Q1. What is formed on the other side of the Moon?
3.
Place the Earth one footstep away from the Moon (see drawing below). Make
sure that the Sun, Moon, and Earth are along a straight line. Turn on the
flashlight and observe.
Moon
Sun
1 footstep
Earth
1 footstep
Q2. What is formed on the surface of the Earth?
4.
Place the white paper one footstep away from the Earth (see drawing below).
The white paper must be facing the Earth. Observe what is formed on the
white paper.
Earth
Moon
Sun
1 footstep
1 footstep
Q3. What is formed on the white paper?
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1 footstep
5.
Ask a group mate to move the Moon along a circular path as shown below.
Circular path
Q4. What happens to the shadow of the Moon as you move the Moon around the
Earth?
Q5. Observe the appearance of the Moon. What is the effect of the shadow of the
Earth on the Moon as the Moon reaches position X (see drawing above)?
You have just simulated the formation of shadows of astronomical objects in
space. The formation and darkening is exactly the same as the formation of shadows
commonly seen around you. When shadows are formed on astronomical objects, a
darkening effect is observed. This phenomenon is called an eclipse.
How Do Eclipses Happen?
In the earlier grades, you learned about the members of the solar system.
You know that the Sun gives off light. As the different members of the solar system
move around the Sun, they block the light from the Sun and form shadows. What this
means is that planets have shadows, and even their moons have shadows, too. But
we cannot see the shadows that they form because we are far from them. The only
shadows that we can observe are the shadows of the Moon and Earth.
Figure 6. Look at the shadows of the Moon and Earth. Where does the shadow of
the Moon fall? Where does the shadow of the Earth fall?
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Look at Figure 6. (Note that the objects are not drawn to scale.) In the
drawing, there are two Moons. Of course, you know that we only have one Moon.
The figure is just showing you the Moon at two different locations as it goes around
the Earth.
The figure shows where the shadows of the Moon and Earth are as viewed in
space. But here on Earth, you cannot observe these shadows. Why? Look at the
shadow of the Moon in positions A and B. In position A, the Moon is too high; its
shadow does not fall on Earth. In position B, the Moon is too low; the shadow of the
Earth does not fall on the Moon. The shadows of the Earth and Moon are cast in
space. So, when can we observe these shadows? In what positions can we see
these shadows? Let us look at another arrangement.
Figure 7. When does the shadow of the Moon fall on Earth? When does
Earth cast a shadow on the Moon?
In Figure 7, the Earth has moved along its orbit, taking the Moon along. The
Moon is shown in two different locations once more. Note that at these positions, the
Moon is neither too high nor too low. In fact, the Moon is in a straight line between
the Sun and the Earth. You can say that the three objects are perfectly aligned.
At position A, where does the shadow of the Moon fall? As you can see, the
shadow of the Moon now falls on the Earth. When you are within this shadow, you
will experience a solar eclipse. A solar eclipse occurs when the Moon comes
directly between the Sun and Earth (Figure 7, position A). You have simulated this
solar eclipse in Activity 3.
Figure 8. Where is the Moon in relation to the Sun and Earth during a solar
eclipse?
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Let us look at the Sun, Moon, and Earth in Figure 8. Look at the tip of the
shadow of the Moon as it falls on Earth. Is the entire shadow of the Moon completely
dark? Do you notice the unequal shading of the shadow? Actually this unequal
shading is comparable to what you have observed in your simulation activity.
Remember the shadow of the
small ball (Moon) on the big ball
(Earth) in your activity? It has a gray
outer part and a darker inner part
(Figure 9). In the case of the Moon’s
shadow, this gray outer region is the
penumbra while the darker inner
region is the umbra.
If you are standing within the
umbra of the Moon’s shadow, you
will see the Sun disappear from your
view. The surroundings appear like it
is early evening. In this case, you are
witnessing a total solar eclipse. In
Figure 9. Is the shadow of the small ball
comparison, if you are in the
uniformly dark?
penumbra, you will see the Sun
partially covered by the Moon. There
are no dramatic changes in the surroundings; there is no noticeable dimming of
sunlight. In this case, you are observing a partial solar eclipse.
Let us go back to Figure 7. Look at the Moon in position B. Do you notice that
at this position the Moon is also aligned with the Sun and Earth? At this position, a
different type of eclipse occurs. This time, the Moon is in the shadow of the Earth. In
this case, you will observe a lunar eclipse. A lunar eclipse occurs when the Moon is
directly on the opposite side of the Earth as the Sun.
The occurrence of a lunar eclipse was simulated in the activity. Do you
remember the small ball (Moon) in position X? You noticed that the shadow of the
big ball (Earth) darkened the whole surface of the small ball. In a lunar eclipse, the
shadow of the Earth also darkens the Moon (Figure 10).
Figure 10. Where is the Earth in relation to the Sun and Moon during a
lunar eclipse?
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Focus your attention on the shadow of the Earth in Figure 10. The shadow is
wider than that of the Moon. It also has an umbra and a penumbra. Which part of the
Earth’s shadow falls on the Moon? Is the Moon always found within the umbra?
The appearance of the Moon is dependent on its location in the Earth’s
shadow. When the entire Moon is within the umbra, it will look totally dark. At this
time you will observe a total lunar eclipse. But when the Moon passes only through a
part of the umbra, a partial lunar eclipse will be observed. A part of the Moon will look
dark while the rest will be lighter.
In earlier grades, you learned that it takes about one month for the Moon to
complete its trip around the Earth. If that is the case, then we should be observing
monthly eclipses. In reality, eclipses do not occur every month. There are only about
three solar eclipses and three lunar eclipses in a year. What could be the reason for
this?
The answer lies in the orbit of the Moon. Look at the orbit of the Earth and the
Moon in Figures 6 and 7. Do their orbits have the same orientations? As you can see
the Moon’s orbit is slightly inclined. The orbit is tilted by 5 0 from the plane of the orbit
of the Earth. As the moon moves around the Earth, it is sometimes higher or lower
than the Earth. In these situations, the shadow of the Moon does not hit the surface
of the Earth. Thus, no eclipses will occur. Eclipses only happen when the Moon
aligns with the Sun and Earth.
Facts, Myths, and Superstitions
Some people believe that a sudden darkening during the day (solar eclipse)
brings bad luck. Others say that it is also bad luck when the Moon turns dark during
a Full Moon (lunar eclipse).
Do you think these beliefs regarding eclipses are true? Let us find that out in
the next activity.
Activity 4
Does a Bakunawa cause eclipses?
Objective
When you finish this activity, you should be able to evaluate some beliefs about
eclipses.
What to do
1. Collect some beliefs about eclipses. You may ask older people in your family or
in the community Or, you may read on some of these beliefs.
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Table 2. Beliefs related to eclipses and
its scientific bases
Beliefs
Scientific
explanations
Ancient Tagalogs call eclipses as
laho. Others call it as eklepse
(pronounced as written). Old people
would tell you that during laho or
eklepse, the Sun and the Moon are
eaten by a big snake called
Bakunawa. The only way to bring
them back is to create a very loud
noise. The Bakunawa gets irritated
with the noise and spews out the
Sun and the Moon back to the
people.
Q1. Which beliefs and practices have scientific bases? Why do you say so?
Q2. Which beliefs and practices have no scientific bases? Support your answer.
Which among the beliefs you have collected do you consider true? Do all the
beliefs you have collected have scientific bases? Are the explanations of the
occurrences of eclipses related to these beliefs? Are there any proofs that tell you
they are true?
In science, explanations are supported with evidence. Beliefs related to
eclipses, such as the Sun being swallowed by Bakunawa (a large animal), or the
increase of harmful microorganisms during an eclipse, are passed on by adults to
young children. But until now, no proof has been offered to show that they are true.
However, there are beliefs that have scientific bases. For example, it is bad to
look directly at the Sun during a solar eclipse. Doing so will damage your eyes. This
is true. Even if only a thin crescent of the Sun is left uncovered by the Moon, it will
still be too bright for you to observe. In fact, it is 10,000 times brighter than the Full
Moon and it will certainly harm your retina. So if you ever observe a solar eclipse, be
ready with a solar filter or welder’s goggles to protect your eyes.
Now you are an informed student on the occurrence of eclipses. The next
time an eclipse occurs, your task is to explain to your family or the community the
factors that cause eclipse.
Summary
You may still be wondering why the topics Seasons and Eclipses were
discussed together in a single module. The reason is that these phenomena are
mainly the result of the motions of the Earth and Moon through space. As the Earth
goes around the Sun, the northern and southern hemispheres are alternately
exposed to the direct rays of the Sun, leading to the annual changes in seasons. And
as the Moon goes around the Earth, it sometimes forms a straight line with the Sun
and Earth, leading to the occurrence of eclipses. We do not directly see nor observe
the motions of the Earth and Moon, but we can observe the phenomena that arise
because of them.
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