CHEM 304
CHEMISTRY IN THE CLASSROOM
LABORATORY MANUAL
Winter, 2004
Course Goals
The basic concepts of chemistry as related to the elementary and middle school classroom are presented.
Using guidelines described in the State of California Science Content Standards (adopted October, 1998
and available at http://www.cde.ca.gov/be/st/ss/scmain.asp) the major themes underlying science, such
as structure, patterns of change, energy, stability, and systems and interactions are developed. Chemical
concepts include elements, compounds and mixtures, states of matter, physical and chemical changes,
transformation of matter, acids and bases, chemical identification, energetics and kinetics. The course
presents chemistry using the student's own experiences with common chemicals, with its application in
technology and its implications for society. The laboratory, using common household chemicals,
provides students with a hands-on laboratory experience where they make associations between new
ideas and their previous conceptions of how the physical universe works. Most Experiments performed
in the laboratory are appropriate for the elementary classroom and can serve as reference materials for
the new elementary school teacher. In laboratory, students learn how to perform and design experiments,
tabulate and graph data, and present their findings orally. Safety in the elementary science curriculum,
including preparation and disposal of chemical reagents is emphasized.
Educational Objectives
1. Use the scientific method to observe, experiment and hypothesize.
2. Describe a variety of graphic changes that clarify the concepts of a physical and chemical changes.
3. Perform common laboratory manipulations of reagent transfer, volume measurement, filtration and
determination of physical properties of weigh, volume and density.
4. Observe the particulate nature of matter, use and evaluate Internet Science Sites for Education.
5. Describe the three states of matter (solid, liquid, gas) and how one state is converted into another
state (physical changes in matter).
6. Describe atomic structure in terms of protons, neutrons and electrons. Understand how emitted light
can be used to identify an element.
7. Describe both physical and chemical properties of elements, compounds and molecules. Use the
periodic table to understand chemical families and periodicity.
8. Explain bonding in terms of ionic, non-polar covalent and polar covalent. Understand the difference
in polar vs. non-polar molecules and the solubility rule of "Like Dissolves Like."
9. Perform simple qualitative tests using common household chemicals. Study thermodynamic and
kinetic variables of chemical reactions
10. Explain the fundamental chemical principle of acidity, pH and neutralization.
11. Understand the universal role of chemistry in our daily life by studying proteins, carbohydrates, fats
and genetic material.
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Materials and Safety Information For Chemistry 304
Chemicals Commonly Found At Retail Stores
Acetic Acid (HC2H3O2) has the common name of vinegar. Vinegar is approximately 5 % acetic acid,
the remainder is mostly water. Buy white vinegar from the grocery store. Vinegar is a weak acid with a
strong pungent smell, so use with caution in a well-ventilated room.
Acetone (C3H6O) is a highly flammable liquid which is miscible with water. Nail polish remover is
mostly acetone, and it will dissolve both polar and non-polar compounds. Acetone is both flammable
(keep away from open flames!) and toxic if ingested in any amount, or if inhaled in excessive amounts
Alum is a generic name for several compounds containing aluminum and sulfate. One of these,
AlNa(SO4)2, has the common name sodium alum or soda alum. It is used for making pickles and as a
deodorant (available in supermarkets and drug stores). Several different kinds of alums can be used
interchangeably for growing beautiful crystals.
Ammonia Water (NH4OH) is a colorless, intense, pungent solution. It is made by dissolving ammonia
gas (NH3) in water. It is used as a window cleaner and as a detergent.
Ammonium Chloride (NH4Cl) is also known as sal ammoniac or salmiac. This colorless, saline tasting
solid is hygroscopic (absorbs moisture from the air) and has a tendency to cake. It is used for ice cream
making (NOT IN THE ICE CREAM!!!) and for snow treatment (slows melting on ski slopes).
Ascorbic Acid (C6H8O6) is Vitamin C. It is isolated from citrus fruits, such as lemons and paprika. Use
the unflavored white tablets containing a starch binder.
Bleach is a solution of sodium hypochlorite (NaOCl) in water. Some bleaches contain additional
ingredients including detergents and scents. Sodium hypochlorite is a strong oxidizing agent, and is very
toxic if swallowed. Bleach can cause skin irritation, and reacts to give off toxic chlorine gas when
combined with acidic substances, including some other cleaning products.
Boric Acid (H3BO3) is used in weatherproofing, fireproofing and as an insecticide. It is toxic, and
should not be ingested or stored near food. It can be found in the local drugstore.
Bromothymol Blue (BTB) is an indicator solution used to test the pH of pools. The indicator turns
yellow in acids, blue in bases, and green in neutral water. It is available in pool supply centers.
Calcium Chloride (CaCl2) is a salt closely related to sodium chloride. (Not for use as table salt!) It is
known as ice cream salt and is used in large quantities during the winter to melt ice on streets. Calcium
chloride should be kept in tightly closed containers because it is hygroscopic, meaning that it absorbs
water from the atmosphere.
Calcium Carbonate (CaCO3) is found in chalk, marble chips, limestone, eggshells, and seashells.
Calcium Sulfate (CaSO4) is also known a Plaster of Paris. In its dehydrated form (as purchased in craft
stores) it can cause burns to the skin--always handle with gloves! The dust can also cause burns to your
mucus membranes if inhaled.
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Carbonic Acid (H2CO3) is found in club soda and is the fizz in soda pop. When a solution of carbonic
acid is left open, it decomposes to carbon dioxide and water.
H2CO3 ⇔ H2O + CO2
Carbon Dioxide (CO2) is commonly known as dry ice. It is -78°C, cold enough to cause severe frostbite
if handled by unprotected hand. DO NOT TOUCH! Dry ice can be purchased from an ice company for
$0.75 per pound. Exhaled breath contains some carbon dioxide.
Citric acid (HC6H7O7) is an acid that comes form organic sources such as fruits. It is a common food
additive that is very sour in its pure form. It is a white solid that readily dissolves in water. It can cause
irritation if it gets into eyes or noses.
Copper Sulfate (CuSO4) or blue vitriol is a toxic substance used to kill algae in swamp coolers, and is
available in pool supply stores.
Diatomaceous Earth is a white material derived form the silica shells of microscopic organisms called
diatoms. It is mined from sedimentary deposits, ground to a fine powder and used for filters and
polishers. It is inert, but can cause irritation if it gets into your eyes and nose.
Epsom Salts (MgSO4.7H2O) occurs in nature as the mineral epsomite. Efflorescent crystals are used
externally in local inflammation and infected wounds. Available in drug stores. Not to be taken
internally.
Denatured Ethyl Alcohol (C2H5OH) is made by the fermentation of starch, sugar, and other
carbohydrates. In the laboratory, alcohol is denatured by adding methyl alcohol or isopropyl alcohol
(both are poisons). Denatured Alcohol in not for consumption.
Hydrochloric Acid (HCl) or muriatic acid is a solution of HCl gas in water. Concentrated solutions
cause severe burn and permanent visual damage may occur if solution come in contact with eyes.
Fumes cause coughing, choking, and ulceration of the respiratory tract. Hydrochloric acid is available in
pool supply stores.
Hydrogen Peroxide (H2O2) is sold as a dilute solution in water (available in drug stores), and used as an
antiseptic. Hydrogen peroxide is a strong oxidizing agent and is toxic if ingested.
Iodine (I2) is usually sold as a solution in drug stores. It is bluish-black depending on concentration and
is used as a topical antiseptic. Iodine is extracted from seaweed. Although a small amount of iodine ion
is required for proper thyroid function, the iodine solution you can buy is toxic if ingested.
Rubbing alcohol (C3H8O) is the common name of a 70% solution of isopropyl alcohol in water (used as
a disinfectant). Isopropyl alcohol is toxic if ingested, and flammable.
Magnesium Hydroxide (Mg(OH)2) is a natural mineral brucite which is used as an antacid and
cathartic.
Magnesium Sulfate (MgSO4) is the chemical name for Epsom salts
Plaster of Paris: a powdered form of Calcium Sulfate (see above for cautions).
3
Phenol Red indicator (C19H13O5SNa) is a solution in water, used for detecting pH changes (red is
acidic, yellow is basic) as well as the presence of DNA. Used for checking pH in pools and spas.
Sand (SiO2) is used in the manufacture of glass.
Sodium Bicarbonate (NaHCO3), or baking soda, is a common household chemical used as a leavening
agent in cooking and as a base. It is slightly soluble in water and reacts vigorously with acids to produce
foaming
NaHCO3 + HCl
--------------> H2O + CO2 + NaCl
Sodium Borate (B4Na2O7), also known as borax, is used as a detergent (available in Supermarkets).
Ingestion of 5 to 10 g can cause severe vomiting and diarrhea. In dilute solution, it is an antiseptic and
astringent.
Sodium Carbonate (Na2CO3) occurs in nature as thermonatrite , and is commonly known as soda ash
and washing soda (available in the supermarket). It can be a skin irritant, although in dilute solutions it
is used to cleanse skin suffering from eczema.
Starch ((C6H10O5)n) is a mixture of long chains of glucose, and is how plants store sugars (for example,
corn starch). Starch is used to size fabrics, as a binder in the pharmaceutical industry and as an antidote
for iodine poisoning.
Sucrose (C12H22O11) is common table sugar, also know as cane or beet sugar. One mole of sucrose
contains one mole of glucose and one mole of fructose bonded together. It is used as a sweetening agent
and in the manufacture of soaps and inks.
Sodium Chloride (NaCl) or common table salt, is an essential dietary chemical. It is the main salt in sea
water. Sodium chloride is a white solid which is very soluble in water. Salt is considered toxic, but is
only hazardous if consumed in large quantities.
Sodium Hypochlorite (NaOCl) solution is available as laundry bleach (see above).
WindexTM is the trade name for a cleaner made primarily of ammonia water (see above), and copper
chloride (see above). Cautions mentioned above should be followed.
4
Name
Lab Section
Experiment 1
Scientific Observation
Experiment Objectives:
1. To gain experience in making and recording experimental observations.
2. To develop skill in handling glassware and transferring solid and liquid chemicals.
3. To observe some chemical and physical changes.
4. To become familiar with safety precautions in the laboratory.
Introduction:
Everything in the known universe can be put into one of two categories: matter or energy. Matter is
the material of the universe, and energy is the driving force that makes things happen. Chemistry is the
study of the properties, relationships, and interactions of matter and the energy changes that occur as a
result of chemical interactions. Science can be defined as organized knowledge. Scientific knowledge is
gained by systematically performing thoughtful experiments, carefully recording observations, and
ultimately formulating some conclusion. This procedure is known as the scientific method and involves
three steps:
1. Experimentation - collecting data by observation of chemical changes under controlled conditions.
2. Hypothesizing - formulating a tentative proposal to correlate and explain the observation.
3. Theorizing - stating a formal theory or scientific law after extensive testing of the hypothesis.
Hypotheses are frequently proven invalid, although not always immediately. Historically, chemists and
physicists have been slow to abandon an acceptable theory in order to adopt a new one. Scientists
exercise caution in drawing conclusions, knowing that nature reveals itself in glimpses and at times
appears contradictory. Hypotheses may be discarded, modified or on rare occasions, after rigorous
testing, be elevated to the status of a scientific theory.
Procedures:
A. Peanut Particulars:
Scientists must observe things they study very closely in order to learn a lot about them. Sometimes
scientists may need to observe the smallest details of an object. Other times they need to observe a
process, such as a chemical reaction or a falling object. This activity should give you some practice
for improving your powers of observation!
Working in groups of 4, give a peanut to each student. Observe your peanut very carefully. Is it
long or short, skinny or chubby? Does it have pointed or rounded ends? Does it make a sound when
shaken? Does it have a pattern of markings or any other special features? Record your observations.
Now mix all the peanuts back together again and try to pick out your peanut based on your
observations. Next draw a detailed picture of your peanut and sign it. Place all the peanuts in a pile
again. Trade drawings so no one has his or her own drawing and try to find the peanut that matches
the drawing. Check with the person who signed the drawing to see if you picked the correct peanut.
After all peanuts are correctly identified, students should tell the student who drew the peanut, what
helped them find the peanut, and how the drawing could be improved. With this new information,
students should make as accurate and detailed a drawing of their peanut as possible and again sign
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their new drawing. Take into account things about your peanut that you did not notice before, as
well as suggestions from your classmates. Next have two groups get together and mix all their
peanuts in a pile. Find your peanut, then trade drawings and find the peanut in the drawing.
B. Instructor Demonstrations:
The following experiments are intended to provide interesting chemical demonstrations. You are to
record your observations in you laboratory manual and then propose a hypothesis to explain the
observations. Then suggest an experiment to test your hypothesis.
1. Money to Burn: Observe the clear solution in the beaker and place a one dollar bill in the
liquid. Remove the dollar and light it with a match.
2. Inflate and Separate: Carefully open a bottle of soda and quickly place a balloon over the
mouth of the bottle. Notice how long it takes the balloon to stand upright. Now fill a large
container half full of hot water. Remove the balloon from the bottle, allow it to deflate, then
quickly place the bottle in the water and put the balloon back on. Again notice how long it takes
for the balloon to stand upright.
3. Copper Smog: Place a piece of copper metal in a large Erlenmeyer flask. Pour enough
concentrated nitric acid into the flask to cover the metal and stopper the flask tightly.
C. Student Experiments:
Record you observations for each of the following experiments in your laboratory notebook.
Propose a hypothesis to explain your observations. Then suggest an experiment to test your
hypothesis
4. Browning Apples: Cut an unpeeled apple into at least 8 wedges. Each pair of students should
take 2 wedges. Crush a vitamin C tablet and sprinkle the powder over the cut surface of one of
the apple wedges. Allow both the apple sections to sit uncovered for one half hour. Observe and
record the results.
5. Copper Nails: Add a few crystals of copper sulfate to 8 ml of distilled water and stir to
dissolve. Place a shiny iron nail in the solution. Wait about 20 minutes, then record your
observations.
6. Hot or Cold: Add a half teaspoon of ammonium chloride to one test tube and calcium chloride
to the other. Half fill each test tube with distilled water. Using a thermometer, measure the
temperature of the sample before and after mixing. Record the temperature change.
7. The Green Blob: Pour 2 ml of iron acetate solution into a glass test tube. Add 3 ml of
household ammonia and stir. Record your observations. (Iron acetate can be made by putting
steel wool into a glass jar and adding enough vinegar to cover the steel wool. Allow the jar to sit
undisturbed for 5 days. The resulting solution is iron acetate.)
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8. Mixable Unmixables: Pour approximately 100 ml of whole milk into a 250 ml beaker and
approximately 100 ml of skim milk into a second 250 ml beaker. Place on a flat surface and let
stand for two minutes. Carefully add three separate drops of food color to the milk in each
beaker by sliding them down the side of the beaker keeping them as far away from each other as
possible. Observe. (Do the drops remain on the surface? Do they spread out?) Now touch a dry
cotton swab to one of the food color drops in each beaker. Observe. (Did the swab absorb the
drop?) Wet a swab with detergent and touch it to a different food color drop. Observe. (How
did the effect differ from that with the dry swab?) Finally, add a drop of detergent directly into
the middle of each beaker. Observe. (Did the food color drops stay as drops or did they spread
out?) In all your observations, pay particular attention to any differences between what happens
with the two different types of milk.
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OBSERVATIONS AND HYPOTHESES
1. Money to Burn:
Observations:
Hypothesis:
Suggestion for test of hypothesis:
2. Inflate and Separate:
Observations:
Hypothesis:
Suggestion for test of hypothesis:
3. Copper Smog:
Observations:
Hypothesis:
Suggestion for test of hypothesis:
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4. Browning Apples:
Observations:
Hypothesis:
Suggestion for test of hypothesis:
5. Copper Nails:
Observations:
Hypothesis:
Suggestion for test of hypothesis:
6. Hot or Cold :
Observations:
Hypothesis:
Suggestion for test of hypothesis:
9
7. The Green Blob:
Observations:
Hypothesis:
Suggestion for test of hypothesis:
8. Mixable Unmixables:
Observations:
Hypothesis:
Suggestion for test of hypothesis:
10
Name
Lab Section
Experiment 2
Mixtures: Homogeneous and Heterogeneous
Experiment Objectives:
1. Investigate the behavior of solids in water and gain an understanding of homogeneous and
heterogeneous mixtures.
2. Demonstrate the concept of density.
3. Gain experience with the separation techniques of flotation, magnetic separation, filtering, sifting
and recrystallization.
Introduction:
When two or more kinds of matter are put together, the result is a mixture. These mixtures can be
classified as homogeneous, where the components are distributed uniformly throughout the mixture
(such as salt dissolved in water), or heterogeneous, where the distribution is not uniform (such as
sand and water). Sometimes when two or more materials are mixed, a special kind of homogeneous
mixture results. For example, when sugar is added to water it seems to disappear. This process is
called dissolving, the result is a solution. A solution is composed of a solute (gas, liquid, or solid)
and solvent (liquid). Like all mixtures, solutions can be separated, not by hand or with a filter, but
by evaporation. Solutions can be made from the same materials, but in different concentrations.
Solutions with a high ratio of solute to solvent are concentrated solutions. Solutions with a little
solute are called dilute. Most solutions reach a point of maximum concentration where no more
solute can be dissolved and are said to be saturated. The above change is called a physical change,
because even though the size of the particle may change, it is still the same material.
Procedure and Results:
In this experiment, you will apply five standard methods of separation to analyze and purify a simple
mixture of solids: magnetic separation, flotation, sifting, filtering and recrystallization. The
instructor will briefly describe each of the pure substances before they are added to the mixture. You
should record the color, particle shape, and size and any other unique characteristics of the substance
in chart.
Substance
Color
Shape
Sodium Chloride
Iron
Pebbles
Styrofoam
Diatomaceous Earth
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Size
Other
1. Add about 1 teaspoon of each solid to form a mixture in a 250-mL beaker. Using a magnet, remove
and put aside any substance(s) that you can. Which substance(s) did you remove using this method
of separation?
2.
Add 50 mL of water to the beaker. Stir and observe. What substance(s) formed a solution with
water?
3.
Which substance(s) formed a heterogeneous mixture with water?
4.
Can you skim off any substances? Which substance (b) did you remove using this method of
separation?
5.
Using your wash bottle, rinse off the skimmed substance.
6.
Next, use a screen to separate the larger insoluble substance from the mixture. Which substance (c)
did you separate using this method?
7.
Don't forget to wash off the material on the screen with a little water from your wash bottle.
8
Now, pour the mixture through a coffee filter. Wash any residue remaining in the beaker with your
wash bottle, then wash the coffee filter. Which substance (d) was collected in the filter paper?
9.
Only one substance remains in the aqueous (water) layer. What is it?
10. To separate the sodium chloride from the water, we will perform a recrystallization by letting the
water evaporate. Mark you beaker with your name and place it in the fume hood until the next
laboratory period. When you return, record your results.
11. Summarize your results on the following flow sheet. In each box with a letter, write the material
removed during that step. In the other boxes, write the materials that remain in the mixture.
Flow Chart for the Analysis of a Simple Mixture
Sodium Chloride
Iron
1. Magnet
Pebbles
Styrofoam
Diatomaceous
Earth
c.
a.
4. Screen
2. Water
3. Skimmer
d.
e.
6. Recrystallization
12
b.
5. Filter
12. Define a heterogeneous mixture and give two examples.
13. Define a solution and give two examples.
14. How could you speed up the recrystallization?
Density Tower:
1. Cover your work surface with a layer of paper towels. Add 40 mL of water to two of your plastic
beakers. Add 1 drop of blue food coloring to each beaker of water and stir.
2. Now add 40 mL of corn syrup to the first cup of water and 40 mL of vegetable oil to the second cup
of water, by pouring these liquids over the back of a spoon and into the cups. Record you
observations in the Cup Chart Below. Does the corn syrup appear to be above or below the
water?________________ Is the corn syrup more or less dense than the water ?_____________
How can you tell? _______________________________________
3. Look at the cup containing the water and the oil. Is the oil above or below the water? ____________
Is the oil is more or less dense that the water? ______________
How can you tell? ________________________________________________________________
4. Make a prediction: What do you think will happen when you put some corn syrup and some oil in
the third cup? _________________________________________________________
Why?______________________________________________________________________
5. Test your prediction by putting 40 mL of oil in a third cup. Next add 1 drop of yellow food color to
40 mL of corn syrup and mix, add this mixture to the oil in the third cup. Is the corn syrup above or
below the oil? _____________________ Record your observations in the Cup Chart.
Contents
CUP 1
40 mL blue water +
40 mL corn syrup
CUP CHART
CUP 2
40 mL blue water +
40 mL oil
Observations
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CUP 3
40 mL oil +
40 mL yellow corn syrup
6. You should now have enough information to be able to make your Density Tower. Carefully
dispose of the liquids in your three plastic beakers. Wash and dry them. Put 40 mL of oil into one
of the clean beakers, 40 mL of water into the second cup and 40 mL of corn syrup into the third.
7. Add 1 drop of blue food coloring to the water, 1 drop of yellow food coloring to the corn syrup.
Now stir the liquid in each cup and pour the liquid that you think will remain on the bottom into a
250 mL beaker. Carefully add the second liquid that should float on the bottom liquid. (Don’t Stir!)
Now, pour in the third liquid that should float on the other two liquids. You’ve created your first
density tower. Now, take several items from the chemical prep cart, such as a candle, Q-tip and
marble. Hold the object in your hand and predict the relative density of each item. Now, drop the
items into your density column.
Object
Relative Density (prediction)
Relative Density (Experimental)
1.
2.
3.
Were your predictions correct?
Candy Chromatography. Sometimes scientists have a mixture of chemicals and need to know what
each chemical in the mixture is. One way scientists can separate chemicals in a mixture is by a process
called chromatography. In this activity, you will use chromatography to separate the substances used to
color candy.
1. Use a pair of scissors to cut 3 strips of coffee filter about 10 cm long and 3 cm wide. Select 3
different color M&M's (1 should be brown). Write the color of each candy on a separate strip. The
name should be written near the top end of the strip.
2. Pour water about 1 cm deep into a beaker. Dip one end of a cotton swab into the cup and gently wet
one side of one of your candies. Gently rub the candy’s wet side onto its filter strip about 1.5 cm
from the end to make a small dark dot on the paper. Do not put the used end of the cotton swab
back in the water.
3. Repeat step 2 for your other two candies and paper strips. Use a clean cotton swab each time. Be
sure to make your dot dark, on the opposite end of the strip from the name of the candy, and about
1.5 cm from the end of the strip.
4. Carefully place your strips in the cup of water so that only a small portion of the bottom of each strip
touches the surface of the water. Be sure your colored dot is above the surface of the water. Bend
the rest of the strip over the rim of the cup to keep the strip in place.
5. Observe each strip as the water moves up through the dot. What do you notice happening?
Which of the colors on the candies was a mixture of other colors?
What were these colors?
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Density of Liquids and Solids:
Density is a physical property of matter that is defined as the mass per unit volume. In equation form,
this expression can be written as
Density (d) = mass (m) / volume (v) = mass (g) / volume (mL)
To determine the density of an object, the mass (grams) and volume of the object must be determined.
The mass is obtained by weighing the object on a balance. The volume can be obtained using calibrated
glassware or by measurement using a ruler. After collecting the data, the density is calculated from the
ratio of the mass to volume.
1. Determination of the density of water: The density of water will be determined by an indirect
technique called weighing by difference. First, weigh an empty 10-mL graduated cylinder. Next,
add 10 mL of water to the graduated cylinder and reweigh. The mass of the liquid is found by
subtraction.
a. Mass of empty graduated cylinder
b. Mass of water and graduated cylinder
c. Mass of water (b - a = c)
_______________g
_______________g
_______________g
Now, divide the mass of water by the volume of water
Mass of water
_____________g ÷
Volume of water
_____________mL
= Density of water _____________g/mL
2. The volume of an irregular object cannot be found directly, but indirectly by the amount of water it
displaces. Select a rubber stopper and determine its mass in grams. Record the mass in the data
table below (a). Now, place about 30 mL of water in a 50-mL graduated cylinder and record the
exact level in the table below (b). Now introduce the stopper into the graduated cylinder. Determine
the new water level in the graduated cylinder and record this value in the data table below (c).
Determine the volume of the stopper (c - b = d) and record this in the data table below (d).
a.
b.
c.
d.
Mass of rubber stopper
Beginning water level
Final water level
Volume of stopper
____________g
____________mL
____________mL
____________mL
Now, divide the mass of stopper (a) by the volume of stopper (d)
Mass of stopper
Volume of stopper
= Density of stopper
_____________g ÷
_____________mL
_____________g/mL
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3. To determine the density of an unknown rectangular solid, obtain an unknown solid and record its
identity (wood, metal, glass, etc.) in the Data Table below. Weigh the unknown solid and record its
mass. Measure the length, width and thickness with a metric ruler. Record the data and determine
the volume of the rectangular solid. Now calculate the density of the solid.
Unknown material ___________
a. Mass of rectangular solid
b. Length of solid
c. Width of solid
d. Thickness of solid
e. Volume of solid
______
Length
____________g
____________cm
____________cm
____________cm
_____
x
Width
x
________
Thickness
Now, divide the weight of solid (a) by the volume of solid (e)
a. mass of solid _____________g ÷
e. volume of solid ____________cm3
= Density of Unknown __________g/cm3
16
=
______
Volume
Name
Lab Section
Experiment 3:
Atoms and States of Matter
Experimental Objectives:
1. To practice evaluating Internet sites for science education.
2. To view atomic and molecular surface images.
3. To observe the particulate nature of matter.
4. To observe the different states of matter and changes between them of various substances.
5. To observe the energy released or absorbed in changes of state.
Part I: Computer Laboratory
Work in groups of 2-3 to complete the following:
1. Visit at least five sites for chemistry or science educators, starting from the Chem 304 "Links" page.
http://chem.csusb.edu/~chem304/studentresource/304links.htm (it is easier just to go to
http://chem.csusb.edu/ and follow the links from there. List the URLs (Universal Resource Locators,
e.g. http:// ....) visited. Some of the sites you visit may result from outside links from the sites on the
Chem 304 page. This is OK.
2. Write a short but critical evaluation of the best and worst site visited, as applies to K-6 science
educators. Criteria used to judge the site might include appropriateness of level of science, validity
of scientific content, visual appeal of site, ability of site to stimulate class discussion or activities.
Although your group of 2-3 students should discuss these sites as you visit them, each student is
responsible for writing approximately one paragraph summary in her/his own words of the best and
worst sites.
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3. Visit the "STM" site (http://www.almaden.ibm.com/vis/stm/catalogue.html) that shows "artwork"
created using scanning tunneling microscopy of atomic surfaces. Which is your favorite? How do
scientists "see" such small things as individual atoms? (Check the "lobby" or ask your instructor).
Part II: In the Laboratory
Experiment A: Lose Some Weight-Evaporate
Procedure: Warning! Rubbing Alcohol is flammable and is poisonous if swallowed. Read and
follow all precautions on the label.
You will need: 2 plastic cups, 2 Styrofoam cups, 1 straight pin, 1 plastic drinking straw, 1 paper towel,
rubbing alcohol, water, metric ruler, scissors, tablespoon
1. Measure the length of a straw and push a pin through the exact center of the straw.
2. Stand two 2 Styrofoam cups near each other on the table and rest the pin on the rims of the two
cups to make a balance. If the straw is not well-balanced, push the pin through the straw again in
a slightly different spot.
3. Pour about 2 tablespoons of water into one of the smaller cups. Pour about two tablespoons of
rubbing alcohol in the other smaller cup. Be sure to replace the cap on the alcohol bottle.
4. Cut 2 strips of paper towel measuring 2.5 cm wide and 15 cm long.
5. Dip one strip in the cup of alcohol while you dip the other strip in the cup of water. Make sure
both strips get completely wet.
6. Take your strip out of the water and have your partner take the strip out of the alcohol. Touch
the strips to the inside of the cups so that some of the excess liquid drips off.
7. Hang your water strip on one end of the straw while your partner hangs the alcohol strip on the
other end. Move the strips on the straw until the straw is balanced again.
8. Watch the straw as the water and the alcohol evaporate. Which side seems to be losing weight
the fastest?
What is causing one side to lose weight faster than the other?
Does water or alcohol evaporate faster?
18
Experiment B: Chilling Effect.
In this experiment we are going to study the effects of temperature on the liquid inside a
thermometer.
You will need: Thermometer, cotton, rubbing alcohol.
1. Lay a thermometer on a table undisturbed for three minutes. This will allow it to register the
room’s temperature. Record this temperature. Now blow you breath across the thermometer
bulb about 15 times. Record your observation.
Room temperature _________________.
Breath temperature _________________.
2. Moisten a cotton ball about the size of a walnut with rubbing alcohol. Spread a thin layer of the
wet cotton across the bulb of the thermometer and record the temperature. Blow you breath
across the wet cotton about 15 times. Record your observation.
Initial temperature of thermometer _________________.
Temperature after blowing breath __________________.
Why does the temperature go up in part 1 and go down in part 2 of the above experiments?
Experiment C: Dew Drop Inn
The Dew Drop Inn is a hotel with a problem. In the winter it is colder outside the hotel than inside,
and water forms on the inside of the windows. In the summer it is cooler inside the hotel than
outside, and water forms on the outside of the window. Can you explain why? The following
experiment may help you figure it out.
You will need: Erlenmeyer flask with lid, ice, water.
1. Put hot tap water in the flask until it is half full. Put the lid on the flask and place it on a table.
Watch the sides of the flask. Is water forming on the inside or outside of the flask?
2. From what you have learned about evaporation and condensation. Can you explain why?
3. Pour the water out of the flask and dry the inside and outside. Now fill the flask half way with
cold tap water and add ice cubes to make the water really cold. Put the lid on the flask and place
it on the table. If you do not see any water drops forming, place the flask in the fume hood. This
time, are the water drops forming on the inside of the flask or on outside of the flask? Can you
explain why?
Is this last flask like the Dew Drop Inn windows in the summer or winter?
19
Experiment D: Frosty the Snow Can
In the Dew Drop Inn, you saw that water molecules as a gas in the air will change into liquid water
on the outside of a container if it is cold enough. You have learned that this process of changing
form a gas to a liquid is called condensation. Let’s see what happens if the container is REALLY
COLD!
You will need; empty metal food can, ice, salt, teaspoon, tape.
1. Dry the outside of the can with a dishtowel. CAUTION: The open can may have sharp and
jagged edges. If you see any jagged edges, use a spoon to press them down against the
inside of the can. Then cover the rim with a double layer of adhesive tape.
2. Place three heaping teaspoons of salt in the can. Fill the can about half way with crushed ice.
Add three more teaspoons of salt. Fill the can almost to the top with ice and add another three
teaspoons of salt. (adding the salt to the ice keeps the temperature of the melting ice lower than
normal, making the surroundings much colder than ice alone.)
3. Hold the can near the top and mix the ice-salt mixture with a spoon. Keep stirring until you see a
thin layer of frost form on the side of the can.
4. Did you notice any water form on the outside of the can?
5.
Do you think the water molecules in the air could have changed directly to ice?
This is the process that causes frost to form on cold mornings.
Experiment E: Observing particulate phenomenon.
Smelly Balloons: Work in two teams for this activity. Each team secretly chooses one "smelly"
chemical from those provided (such as perfume, vinegar, vanilla, oil of wintergreen, moth balls,
hair spray). Place a very small amount (no more than a drop of liquid or a small crystal of solid)
in a balloon, then carefully blow the balloon up (do NOT inhale from the balloon). Tie off the
balloon. Give your balloon to the other team. Have them try to guess the substance in the your
balloon. If the odor is not immediately apparent, wait a few minutes and try again.
Data for Smelly Balloons:
substance placed in your team's balloon:
length of time need by other team to detect this substance:
substance placed in other team's balloon:
number of guesses needed to make this assignment:
length of time needed to make this assignment:
What is it you are detecting when you smell something?
Explain how you are able to detect the odor of something within the balloon, and why it takes time to do
so.
20
Name
Lab Section
Experiment 4:
Subatomic Particles (Electrons)
Experimental Objectives:
1. To learn about cathode rays and the discovery of the electron.
2. To use a spectroscope to examine the unique spectrum of different elements.
3. To use electricity to cause chemical changes to take place by promoting the transfer of electrons.
4. To explore the properties of static electricity.
Introduction:
The electron was the first subatomic particle described, and the one that most affects the physical and
chemical properties of elements and compounds. The electrons are on the outside of the atom, and thus
most accessible to outside influence. The electrons occupy discrete energy levels ("orbits" in the Bohr
model) around the nucleus. If the appropriate energy is provided, electrons are excited, that is they are
promoted from lower to higher energy levels. When these electrons return to their normal levels, visible
light is emitted. Electrical current is a form of energy transferred by electrons moving through wires.
When electrical current is supplied, the atoms can either loose or gain electrons, as used in electroplating
and electrolysis. Metal ions in solution lack electrons relative to the atomic form of the metal. In
electroplating, a power source such as a battery provides a stream of electrons in order to "ionize"
(remove electrons from) one metal, while "plating out" (adding electrons to) another metal ion to create
a coating on a surface. Electrolysis involves the loss or gain of electrons from ions and molecules in
water. When surfaces of some materials are rubbed, electrons are disturbed, creating areas of excess
electrons (static electricity).
Part I: Computer laboratory
Procedure:
There is an excellent web site devoted to J.J. Thomson's discovery of the electron:
http://www.aip.org/history/electron/. Access this site, and answer the following questions. Although you
may access and discuss the site in groups, the answers should be individual.
Describe the "cathode rays" discovered by Thomson.
List two modern devices that use technology similar to Thomson's cathode ray tube for operation.
Why are electrons most easily studied, and thus the first subatomic particle located? (Hint: think
location)
21
Part II: In-Laboratory Experiments
Experiment A: Colorful Elements
Procedure:
Spectroscopes can be used to determine the unique electronic spectrum for each element, a result of the
individual and discrete arrangement of electrons around each atom. Your instructor will show you how
to use the spectroscopes. Aim the opening in the spectroscope at a fluorescent light in the room, then
look at the nanometer (nm) scale. Using crayons, reproduce the lines in the spectrum you see on the
graph below. Draw only the most intense lines.
Now, look at the element sources provided by the instructor (again aiming the opening of the
spectroscopy at the light source). Write the identity of the source in the box above the numbers.
Which element source(s) best match(es) the fluorescent light drawing you made?
What does that say about the elemental composition of the gas in the fluorescent bulb?
22
Experiment B: Copper Coated Nickel (Note this experiment requires observations for 1 hour)
Procedure:
Make a copper penny shiny by soaking briefly in ammonia cleaner, wiping with a cloth, and rinsing
well. Place a nickel coin and the shiny copper penny in the bottom of a 250 mL beaker on opposite sides
(so that they are as far apart as possible).
Touch one end of a wire to the surface of the nickel (must contact the bare wire to the nickel to conduct
electricity); attach a paper clip or tape to the side of the beaker to hold the wire in place. Attach the other
end of this wire to the negative wire of a nine volt battery (black wire). This "negative electrode" (also
called the cathode) is the surface on which the plating will take place.
Touch one end of a second wire to the surface of the clean penny (must contact the bare wire to the
penny to conduct electricity); attach a paper clip to the side of the beaker to hold the wire in place.
Attach the other end of this wire to the positive wire of the battery (red wire). The copper penny will
work as a "positive electrode" (also called anode), by removing electrons from the copper, allowing
copper ions to flow in to the solution.
Carefully pour 50 mL of a solution of Windex into the beaker without allowing the electrodes to touch
each other, but making sure that the wires remain in contact with the coins. (Note: Windex contains
copper ions in it already; the additional copper ions from the penny are not necessary for plating to
occur). Every 20 min. for 1 h write down your observations about (a) the surface of the nickel, (b) the
surface of the penny, and (c) any gas evolution present at either electrode. Electrons are provided by
copper (oxidation) with the help of the battery to turn copper ions from solution (reduction) into a
copper metal coating on the nickel.
Observations:
Experiment C: Water Electrolysis in Yellow, Green, and Blue.
When bromothymol blue is added to water in an electrolytic apparatus, three colored regions are seen.
Bromothymol blue is an indicator that turns yellow in acid, blue in base, and green in neutral solution.
To prepare the water solution, mix 50 mL of tap water, 10 drops of BTB indicator and 1 teaspoon of
solid MgSO4. Prepare a 10% vinegar solution by diluting 1 mL of vinegar to 10 mL with water. Add the
diluted vinegar 1 drop at a time and mix until the solution is green. Assemble the 9 volt battery with
connector and immerse the electrodes in the water solution. Observe the color change during electrolysis
and determine which electrode is the cathode, and which the anode.
Anode (oxidation, electrons removed)
H2O(l) → acid + O2(g) + e–
color of wire
__________
23
color of solution
_____________
Cathode (reduction, electrons gained)
H2O(l) + e– → H2(g) + base
__________
_____________
Experiment D: Static Electricity: Disturbed Electrons
The following two activities demonstrate attractions and repulsion created by static electricity.
1. Cellophane tape.
Place two equal length pieces of clear plastic tape (30 cm each) side by side on a table top, with
about 5 cm of each hanging over the edge of the table. Take one piece of tape in each hand and
quickly rip the tape from the counter, without touching the pieces together. Dangle the two pieces of
tape, and slowly bring them near each other. What happens? Do the strips attract or repel each other?
Do they have like or opposite charges?
Now try this: replace one of the strips on the table surface as before. Run the other strip between
your thumb and finger, rubbing thoroughly (yes, it is sticky!). Remove the first strip from the
counter top, and again bring the two strips together without touching. Now what happens? Do the
strips attract or repel each other? Do they have like or opposite charges?
Develop a third variation on this experiment. Predict what will happen, then test your hypothesis.
Proposed experiment:
Hypothesis:
Observations:
2. Balloons
Suspend two balloons from pieces of string. Each partner rubs his or her balloon against his or her
clothes or hair, then holds the balloon up by the other end of the string. Bring the two balloons
together without touching, and observe what happens. Now touch the two balloons together, then
move them apart again. What happens now?
Cut several small fish (about the size of "fish crackers") from paper. Spread your fish out on a table
or floor. Rub your balloon on a string against your clothes or hair, and suspend the balloon by
holding the other end of the string. Lower the balloon slowly over the fish without touching them.
What happens? (Use more static electricity if you don't see anything happening.) You can turn this
into a counting or arithmetic game, or a "fishing contest" to see who can catch the most fish!
24
Name
Lab Section
Experiment 5:
Periodic Table
Objectives:
1. To observe periodic trends (and deviations of them) using different graphical representations.
2. To observe periodic trends using the Periodic Table game.
3. To classify elements based on their conductivities.
Introduction:
The elements in the periodic table were arranged by Mendeleev according to their increasing atomic
mass (horizontally) and similar properties (especially reaction products with oxygen). With a few
modifications, the modern periodic table presents elements in order of increasing atomic number
(=number of protons), and in groups (columns) with similar physical and chemical properties.
An electrical current is the movement of charged particles through some medium. In a copper wire, the
charge is carried by electrons. Many pure elements can conduct electricity because the arrangement of
atoms allows electrons to move freely. This is a property generally associated with metals.
Part I: Computer Laboratory
Procedure:
From the Chem 304 links page, go to Mark Winter's "Web Elements" site
(http://www.webelements.com). Use the "professional" not "scholar" edition. Notice the layout of the
periodic table. Pick one main group element on the table (in groups 1, 2 or groups 13-18), for example
Carbon (atomic number 6). Examine the element's page (be sure to scroll down!). What information is
given?
Find the words "Crystallography" in the left column, then under the heading "Crystal Structure" choose
the words "view pdb image". Scroll down the page, and view the 3-D picture of the crystal of this
element. You may rotate the crystal by holding down the mouse button and moving the mouse while
placed over the picture. Describe what you see. (you can print out this image and attach it, if you wish).
Under "electronic properties" in the left column, choose "atom radii" to see a graphical depiction of
atomic size for all elements in the periodic table (you will have to scroll down to see the full "Web
Elements" atomic size periodic table. How does atomic size vary as you move from left to right
(increasing atomic number) within a period (horizontal row) of the table?
25
How does atomic size vary as you move from top to bottom of a group (vertical column) of the table?
You can view this same trend in a variety of different graphical formats by doing the following:
1. Click on the "view" button to the left of the words "atomic radius (empirical)" located just above the
graph of atomic radius/periodic table you were just looking at. Choose "line" and examine the trends
of atomic size vs. atomic number. Describe what you see.
2. Choose at least two other formats for displaying the same data (under "Full Table Charts"), and
describe which one is best and which is worst at illustrating the periodic trends of atomic size vs.
atomic number and atomic size vs. position on the periodic table.
There are many other atomic properties that show periodic trends, and that can be viewed graphically
using this web site. One of these is density. Go back to the page with your element to look for density
(keep clicking on the "BACK" button on your Browser until you reach your element's page). Under
"physical properties" (left column) choose "bulk properties". Scroll down until you see the "View"
button to the left of the words "density of solid". Click on the "view" button and select "Cityscape"
format see a color-coded periodic table showing density as a function of position on the periodic table.
Describe what you see.
Now view the same data in "balls" format, and any other formats you wish. Describe how the density of
an element changes as you go through each period (left to right in a row) on the periodic table.
Describe how it varies in most groups (from top to bottom in a column).
Go to the Group Charts section (on the left) and select individual group charts for Groups 1, 2, 13, 14,
15, 16, six of the 8 main group(s) Which of these groups are exceptions to the general trend? This is a
case where the Periodic Law is imperfect.
26
Part II: In the Laboratory
Part A: Conductivity
Procedure:
Prepare a conductivity apparatus as directed by your instructor, using a Christmas tree bulb and 9V
battery. Test to see if the apparatus is working by touching the two bare wires together (the light bulb
should light when the circuit is complete).
Draw a picture of the working conductivity apparatus in the space below. Show and label all parts.
Using the conductivity apparatus, determine whether the following elements conduct electric current and
if so, roughly how well. Perform the test by placing both wires onto a small sample of the chemical
(without touching the wires to each other!). Then find the elements in the periodic table and determine
whether they are metals or non-metals.
Chemical Substance
a)
b)
c)
d)
e)
f)
g)
Conductivity
Yes
No
____
____
____
____
____
____
____
____
____
____
____
____
____
____
Aluminum (Al)
Carbon (C)
Iron (Fe)
Zinc (Zn)
Sulfur (S)
Copper (Cu)
Iodine (I2)
Metal Non-metal
____
____
____
____
____
____
____
____
____
____
____
____
____
____
Sometimes, one property is not alone sufficient to classify a substance. For which of the elements that
you tested did the classification based on the conductivity results differ from that indicated from the
periodic table?
Now test three items in the classroom and predict if they are metals or non-metals based on the
conductivity test. Remember, these may not be elements
h)
i)
j)
Yes
____
____
____
No
____
____
____
Metal
____
____
____
Non-metal
____
____
____
27
Neither
____
____
____
Part B: A Periodic Table Game!
Scientists who study chemistry have their own system of classification. Chemists need to know about
the different atoms that make up all the different living and nonliving things on earth. Just as biologists
place animals that have similar characteristics together into groups, chemists place atoms that have
similar characteristics together into groups. All these groups are organized into a big chart called the
periodic table Because similar atoms can often be used to make similar products and are near each other
on the periodic table, you can use the special periodic table provided to play a search-and-match
chemistry game.
The object of the game is to find two or more elements that are next to each other on the periodic table
and are used to make the same or similar products. They can be side by side, up and down, or diagonal.
For instance, strontium (38) is used in fireworks and so is barium (56), which is directly below it.
Another example is lead (82), which is used to make batteries, and diagonally up from lead is antimony
(51), which is also used in batteries.
Set up a point system to keep score of who finds more elements found in similar products that are next
to each other. Two elements and products next to each other are worth 5 points. Three next to each
other are worth 10, four next to each other are worth 15, and so on. You are encouraged to use your own
knowledge to make connections between elements.
28
Name
Lab Section
Experiment 6:
Crystals and Polymers
Experiment Objectives:
1. To examine the properties of crystalline materials.
2. To prepare materials with new properties by mixing components.
3. To study the properties of some very unusual polymers.
A: Crystal Writing
Introduction: There are many interesting labs for growing crystals. Here is one that can be completed
during your laboratory period. Solutions are saturated when no more solid solute will dissolve in the
liquid solvent. Most solutes will dissolve in greater quantities in hot solvents than in cold solvents.
Crystals will re-form when the volume of solvent is decreased and/or the temperature decreases.
Procedure: Crystal writing
Look carefully at crystals of Epsom salts (formula MgSO4). Describe the shape below.
Now, add 25 mL of HOT water (use caution!) into a 100 ml beaker. Add Epsom salts one spoonful at a
time while stirring, until no more will dissolve. You have now created a saturated solution of this salt.
Record the number of spoonfuls dissolved:
Epsom salts (MgSO4):
spoons
Describe how the solution was formed, in atomic terms. (In terms of what occurred with the water
molecules and the salt ions.)
Now, place a cotton swab into the warm solution. Use the cotton swab to write secret messages on black
construction paper. You will need to go over the writing several times with the cotton swab to ensure
full coverage. Wait 15-30 min. for the crystal message to appear. Describe what you see and compare it
to the shape of the crystals before dissolving.
29
B: Plaster Block
In this experiment, you will observe a phase change due to the addition of water to Plaster of Paris.
Gypsum is a hard shiny crystalline form of calcium sulfate which contains water molecules as part of its
structure. Plaster of Paris is made by heating gypsum to drive off most of its water and grinding the now
soft rock into a powder.
This dry powder changes back into solid gypsum when water is added.
You will need 90 ml of Plaster of Paris, tablespoon, paper cup, Popsicle stick.
1. Pour 90 ml of Plaster of Paris into a paper cup. (Do NOT use your plastic beakers)
2. Add 3 tablespoons of water and stir with the Popsicle stick. Be careful not to place any of the
plaster in the sink as it can clog the drain.
3. Take part of your mixture and form a small ball (about 1 inch diameter), if your mixture is too
runny add a little more Plaster of Paris. Place the ball in another paper cup and cover with water.
4. Squeeze the main cup gently and observe the results every 5 minutes. Record you observations
below.
Start:
5 minutes:
10 minutes:
15 minutes:
20 minutes:
25 minutes:
Summarize your observations:
Give a hypothesis as to what is happening to the Plaster of Paris. Is it hardening due to the water
evaporating?
To check remove the ball of Plaster of Paris from the cup of water. Was the ball able to harden under
water?
Does this behavior agree with your earlier hypothesis? (Explain)
30
C: Gobs of Fun
Scientist not only test substances to find out what chemicals they are made of, they also put chemicals
together in a certain way to make new substances with special characteristics. Sometimes, a very small
amount of a chemical can make a very big difference in the qualities of the final product. Try the
following activity and see that a little bit more or a little bit less can make a big difference!
You will need; cornstarch, warm water, three small beakers, three teaspoons, paper towels, masking
tape, crayon.
1. Cover your work area with paper towels. Use the markings on your beakers to measure. Place 2
level tablespoons of cornstarch (take care not to pack down the cornstarch) in each of the three
beakers labeled A, B and C with a crayon. Add 1 level tablespoon of water to each beaker and stir
until smooth.
2. Add 1/2 extra level teaspoon of cornstarch to beaker A and stir until smooth. Add 1 extra level
teaspoon of cornstarch to beaker B and stir until smooth. Add 1 and 1/2 extra level teaspoons to
beaker C and stir until smooth.
3. Use you finger to scrape up a handful of material from beaker A. As you scrape it up, does the
material at the bottom of the beaker feel different than the material in the rest of the bowl?
4. Describe how the material feels when you squeeze it quickly between your fingers and when it just
sits in the palm of your hand.
5. Rinse off your hands and dry them and repeat step 3 with the material in beaker B. Gather the
material into a glob in one area of the beaker. Does your finger go further into the glob if you poke
it hard or if you push your finger gently into it?
6. Quickly pull some material out of the bowl and hold it. Does it feel and act differently when you
hold it than when you pulled it out?
7. Rinse and dry your hands and make a ball out of the material in beaker C. Does it stay in a ball if
you leave it in the palm of your hand?
8. Is it difficult to make it stay in one shape? How does it act when you pull it apart slowly and when
you pull it quickly?
9. Close your fist quickly around it and then close it slowly and observe the difference.
You can see that a little more or a little less of the chemical in cornstarch and water make a big
difference in the qualities of the final product. Experiment to see if you can find the exact amounts of
water and cornstarch to make the material you like best.
31
D: Hands-On Slime
Imagine exploring a rubbery, viscous substance called Slime with your students. For this activity you
must prepare some of the ingredients in advance. The following materials combine to make enough
slime for 30 students.
The solutions have already been prepared for you so go directly to the "Directions for Students".
You will need: 300 mL of Elmer’s white glue, labeled cups (1 per student), two empty 2-Liter bottles ,
Popsicle sticks (one per student), two tablespoons of borax powder, sealable plastic bags, two liters of
warm water, food coloring, small bottles
Preparation of Solutions:
Dissolve the borax in one liter of warm water and pour the solution into an empty 2-L bottle. Label
this "Liquid A".
Mix the 300 mL of Elmer’s white glue with 300 mL of water and label this "Liquid B”.
Directions for Students:
1. Place 30 mL of solution A into a paper cup. Place 30 mL of Solution B into another cup. At this
point, you may add one or two drops of food coloring to each of solutions A and B.
2. Now mix the two solutions together in a 250 mL beaker and rapidly stir the mixture for 3 –5 minutes
using a Popsicle stick.
3. You should make careful observations about what occurs. Suggest that they hold the substance over
the cup, kneading it until it feels drier. Divide the slime between the two partners so that they each
may explore the properties of the new materials.
Let students discuss the slime-making process.
What changes occurred when you mixed the ingredients?
How is slime like Liquid A and Liquid B?
How is it different from each liquid?
Can you think of any products that are similar to the slime you made?
Note:
Slime should be kept in a Ziploc bag to prevent dehydration (add water and knead in to reconstitute).
Take care with carpets and furniture as the food coloring can leak out.
32
E: Sticky Fingers (for you to do with your students)
What really holds an elementary classroom together? GLUE. Without this mighty adhesive (and its
sidekick paste), many of our favorite activities would literally fall apart. So introduce a little chemistry
and make an inexpensive version of this necessity with your class.
For each group, you will need
1.
2.
3.
4.
125 mL room temperature whole milk.
30 mL Vinegar
cheese cloth
3 g baking soda
5.
6.
7.
8.
2 large plastic cups
graduated cylinder
funnel
water
Procedure:
To begin the glue making procedure, have a student pour the milk into a 600 mL beaker and add the
vinegar. Tell the group to stir the milk and vinegar for two to three minutes. As the stir they will see
small white lumps begin to form. The vinegar (acetic acid) reacts with the milk to denature the protein,
casein. Proteins are polymers or chains of amino acids linked together. We usually refer to casein as
curd and to the liquid remaining as whey. The curds will be smaller than cottage cheese, so tell the
students to look for them carefully.
Next, allow the mixture to settle for a few minutes. While waiting, take some cheese cloth and place it
in a funnel over an Erlenmeyer flask. As one student holds the cheese cloth, another student will slowly
pour the mixture into the filter. Let the liquid whey filter and collect the curds. Each group should now
have a large mass of curd. Take a spoon and transfer the curd from the cheese cloth to another dry
beaker. Add about 8 mL of water and stir. Next add 3 spoons of baking soda to neutralize any
remaining vinegar. Students will be able to see this reaction in the form of carbon dioxide gas. In most
cases, more water will be necessary to make the glue the proper consistency (add in 5 mL increments).
Now that they've finished, ask students to design a fair test that will compare glue strength. For
example, cut several 15 x 2-cm cardboard strips. Instruct your students to apply an even coat of glue to
the bottom 4 cm of one strip, and then place the other strip on top of the first one so that its top 4 cm
overlaps the glued area. Lay a text book on them overnight. The following day, punch a small hole
through the first cardboard strip, 1 cm from the end. They should then place a paper clip through the
hole. While one student holds the top strip, another adds washers one at a time onto the paper clip hook.
Determine which glue is strongest by the number of washers added.
Glue making demonstrates simple chemical reactions, allows students to practice measuring skills and
encourages cooperation among students. The discussion following can include questions about changes
in substances as reactions occur (how are curds and whey different from milk? From the glue? From
commercial glue?). The glue can be used for various activities as well as for further investigations.
33
34
Name
Lab Section
Experiment 7
Bonding: "Water and Salt"
Objectives:
1. To predict whether bonding in a compound is likely to be ionic or covalent, and if a compound is
polar or nonpolar.
2. To determine the electrical conductivities and solubilities of several compounds and to explain these
properties in terms of bond type.
Ionic bonding is when two atoms, or groups of atoms, are bonded together by the electrostatic attraction
that occurs between positive and negative charges. Atoms, or groups of atoms, can acquire a charge by
having an extra electron present (negative charge) or an electron absent (positive charge). Double
charges, and even triple charges are also possible. The charged atoms, or group of atoms, are called
ions. Positive ions are called cations, and negative ions are called anions.
If an ionic compound is dissolved in water or in the liquid state, the ionic bonds are broken, and the ions
are separated from each other. If an electric voltage is placed across such a solution, an electric current
will flow. An electric current is the flow of electrical charge. Positive charges move towards the
negative electrode and negative charges move towards the positive electrode. Thus one way to test if a
compound is ionically bonded or not, is to perform an electrical conductivity test on a solution of the
compound.
Covalent bonding is when two atoms are bonded together by the mutual sharing of a common pair of
electrons. Electrons prefer to coexist in pairs. Thus one pair of electrons in a covalent bond is attracted
to both atoms at the same time, hence the bond. If a compound does not have any ionic bonds, it may
still dissolve in a liquid simply by the separation of the individual molecules from each other. The
molecules do not have any charges associated with them, so the solution will not conduct electricity.
Thus if a conductivity test does not indicate the flow of electrical current, one can conclude that the
compound is bonded solely by covalent bonds, and molecules (not ions) exist in the solution or liquid.
Even if a compound is fabricated with only covalent bonds, the sharing of the electrons which
constitutes the bond may be more or less unequal. This is because different elements have different
affinities for electrons. The atom with the higher affinity for electrons will pull the electrons closer
towards itself and away from the atom with the lower affinity for electrons. This results in partial
charges existing on the atoms. A partial negative charge exists on the atom with the higher affinity for
electrons, a partial positive charge exists on the atom with lower affinity for electrons. This separation
of charge is called a dipole moment. Overall, a molecule may or may not have a total dipole moment,
depending on how all of the individual dipole moments from each of the covalent bonds add together or
cancel each other. Compounds with an overall dipole moment, or separation of charge across the
molecule, are called polar compounds, and those with no overall dipole moment are called nonpolar
compounds.
It is observed experimentally that polar substances can dissolve in polar solvents; and nonpolar
substances can dissolve in nonpolar solvents; but polar substances cannot dissolve in nonpolar solvents
and nonpolar substances cannot dissolve in polar solvents. This rule is often called "like dissolves like".
Water is a polar liquid. Thus any substance that dissolves in water would be considered a polar
compound. Hexane is a nonpolar liquid. Any substance that dissolves in hexane is considered a
35
nonpolar compound. Therefore, a solubility test of various substances in both water and hexane will
determine whether that substance is a polar or nonpolar compound. NOTE: ionic substances may or
may not dissolve in water. Water is a "strong" enough solvent to pull apart the ions in some ionic
compounds. It is not strong enough to pull apart the ions in other ionic compounds. Hexane, or any
other nonpolar solvent, is never strong enough to dissolve an ionically bonded compound.
Experiment A: Conductivity and Solubility
A solution is formed by mixing a solute (the dissolved particle) in a solvent (the dissolving medium). A
solution is a homogeneous mixture if the properties of all parts of the solution are the same. To dissolve
a solute in a solvent, the separate forces that hold the molecules together must be similar to the forces
existing between the solvent and solute. For the solute to be soluble in the solvent, the forces between
the solute molecules must be overcome by similar forces in the solvent. Only then will the particles be
coaxed into moving into the liquid.
Instructor Demo: When determining solubility the rule to remember is “like dissolves like”. Water is
considered a polar solvent. Hexane is considered a nonpolar solvent. When mixed, these two solvents
will form two separate layers (a heterogeneous mixture). Determine which of the following compounds
are soluble in water, and which are soluble in hexane. If the compound to be tested is a solid, use enough
to cover the tip of a scoopula. If the compound is a liquid, use 2-3 drops. For those substances that
dissolve in water, determine whether or not the solutions conduct electricity.
a)
b)
c)
d)
e)
f)
Solubility
Conductivity
Water Hexane
Sodium Chloride (NaCl)
_____ _____
_____
Iodine (I2)
_____ _____
_____
Food Coloring
_____ _____
_____
Sodium Bicarbonate (NaHCO3) _____ _____
_____
Pentane (C5H12)
_____ _____
_____
Sugar (C12H22O11)
_____ _____
_____
Ionic
_____
_____
_____
_____
_____
_____
Nonpolar
Covalent
_____
_____
_____
_____
_____
_____
Polar
Covalent
_____
_____
_____
_____
_____
_____
1. For each compound used in this experiment, predict whether the bonding is ionic, nonpolar covalent,
or polar covalent (put your predictions in the table above).
2. What types of compounds (that is, ionic, nonpolar covalent or polar covalent) would you expect to
a)
be soluble in water?
b)
be soluble in hexane?
c)
conduct electric currents in water solutions?
36
Student experiment: Measure 10 mL of fingernail polish remover (acetone, a nonpolar solvent) in a
small beaker and 10 mL of water in another small beaker.
Determine how many "Styrofoam packing peanuts" dissolve in the acetone _________
and how many in the water _________
Repeat the process using "starch packing peanuts" in acetone _________
and water __________
Describe the polarity of Styrofoam versus starch packing peanuts based on the results of your
experiment.
Experiment B: Conductivity
1. Electrolytes are compounds that conduct electricity when dissolved in water. Substances are
classified as "Strong", "Weak", or "Non" -electrolytes depending on how well they conduct. With a
conductivity tester determine whether each of the following solutions conducts electric current, and,
if so, roughly how well. Perform the test by inserting the prongs (electrodes) of the tester into a
small beaker of the solution. Use a large beaker containing distilled water to rinse off the prongs
between each test. Try to immerse the electrodes by the same amount for each test, to be consistent,
because the more electrode which is exposed the more current which can flow. "Aqueous" solutions
are solutions in which water is the solvent. Write your results next to each compound name (weak
light, strong light, no light) and (weak, strong or non -electrolyte). Wear your goggles!
Sample
Light
Electrolyte?
Pure distilled water (H2O, liquid)
Tap water
Methyl alcohol (CH3OH, liquid)
Hexane (C6H14, liquid)
Salt water (NaCl, aqueous sol'n)
Copper (II) sulfate (CuSO4, aqueous sol'n)
Sugar water (sucrose, C12H22O11, aqueous sol'n)
Ammonia (NH3, aqueous sol'n)
Vinegar (acetic acid, HC2H3O2, aqueous sol'n)
Pentane (C5H12, liquid)
2. Select an unknown and write its letter here _______________. Dissolve a small sample, about the
size of a pea in 5 mL of water and test the electrical conductivity of the solution.
Electrolyte?
Based on the conductivity test result, what type of bonding is present in your unknown?
_____________
37
Experiment C: Hydrogen Bonds and Surface Tension
Compounds containing O-H bonds, like water, can form special types of bonds called hydrogen
bonds. These bonds are responsible for surface tension in water. Hydrogen bonds give water a
skin (surface tension) which allows objects more dense than water, such as water bugs, to walk on
water without falling in. In a hydrogen bond, the hydrogen atom in one water molecule is attracted
to the lone pair electrons of the oxygen atom in another molecule of water. Soap is a surfactant,
which is a substance that lowers the surface tension of water by disrupting the hydrogen bonds.
Let’s study the effects of soap on surface tension.
Related Web Sites
http://wwwepa.gov/owow/NPS/kids/TENSION.HTM
http://www.sme.org/memb/neweek/actsoap.htm
http://www.exploratorium.edu/ronh/bubbles
You will need: a clean shiny penny, dishwashing liquid, paper towel, dropper
1. Rinse the penny thoroughly with water and dry it with a paper towel.
2. Set the penny face up on a table. Place one drop of water on it. What does the drop look like?
3. Carefully add more drops and count how many drops you can add before the water spills over the
edge of the paper. Describe the appearance of the water as you continue to add drops.
4. Dry the penny. Put one drop of dishwashing liquid on the penny. Rub it with you fingers to cover
the entire surface. Wipe off any excess, leaving a significant film of dishwashing liquid on the
penny. Repeat steps 2 and 3. How did the addition of dishwashing liquid change things?
5.
Why?
38
Experiment D: Surfin' Surface Tension
You will need
* Clean, dry baking pan (13 x 9 x 2 in) (lab box top), * 1 white business-size envelop, * 7 small metal
paper clips (new), * pencil, * blunt-tip scissors, * 2 cotton swabs, * liquid dish detergent
1. Fill the lab box top with water. Take a paper clip and hold it by one end and place it in the water.
Does it sink or stay on the surface?
2. Take a second paper clip, hold it by one long edge, and place it in the water. What happens to this
one?
3. Now take the third paper clip and place its flat surface very carefully on the water. Try this until you
can make the paper clip stay on top of the water. (Dry the paper clip between tries.) Observe what
the water looks like around the edge of the skier's clips. Are the clips breaking through the water's
surface?
What do you think is keeping them up?
4. Dip a dry cotton swab into the water at the end of the pan farthest away from the skier. What
happens to the paper clip?
5. Now, dip a cotton swab with dish detergent on it into the baking pan at the farthest place from the
skier. Now what happens? Which swab causes the paper clip to sink? How can you explain what
happens?
6. You can even race a boat because of the surface tension of water. Using an index card, cut out a
little boat like the one in the drawing. Make sure you put a notch in the back of the boat.
7. Place the boat gently on the water and place a drop of dish detergent in the notch. Your boat should
go, go, go! Before you try making and racing any more boats, be sure that you thoroughly rinse out
and dry the pan.
39
Experiment E: Soak Those Sharks
You will need: Brown lab towel and 3 other types of paper towels, blue food color, bowl, scissors, pencil,
thermometer case, metric ruler, tape, spoon
SHARK
1. Trace a shark shape onto the brown lab towel and cut it out. The shark should measure about 15 cm
length. Use this shark shape to cut sharks from the other paper towels. You should now have four
sharks.
2. Tape the sharks' tails to the thermometer case so that the sharks’ tails are evenly spaced across. The
shark’s mouths should be even with each other. Fill the bowl with a half inch of water and add four
drops of blue food coloring. Stir to make a blue ocean in the bowl. Put the ocean on a table.
3. Suspend the sharks so that just their noses are in the ocean up to the notch of the mouth. Record the
time that the sharks took their dive ________.
4. Leave the sharks' noses in the ocean until one shark has absorbed the ocean 1/2 the distance up the
shark. Remove the sharks and record the time here: _______. Lay the sharks on a paper-towelcovered surface and let them dry.
5. Measure the distance from each shark's mouths to the blue line left by the ocean and record those
distances in the chart below. Also, how long did it take for the most absorbent shark to become 1/2
soaked? ________ min. (You'll need this number for the next activity.)
6. Look at the distances you record for each shark in the chart. Which shark was the first one soaked?
If you spilled a glass of milk on the table, which paper would soak up most quickly? Which materials
would you NOT want to use to clean up the spill?
40
Towel 1
Shark Chart
Towel 2
Towel 3
Towel 4
Distance Travel by
Ocean in cm
Distance
Traveled (cm)
7. Take the distances that the ocean traveled on your four sharks and make a bar graph of the
information on the grid below.
Shark 1
Shark 2
Shark 3
Shark 4
Which shark has the taller bar?
Was this shark able to soak up the least or the most blue water?
What can you say about the size of the bars compared to how quickly the ocean traveled up each shark?
41
42
Name
Lab Section
Experiment 8
Chemical Reactions - Mixing Things Up
Experiment Objectives:
1. To become familiar with the evidence for a chemical reaction.
2. To understand the basics of investigative science.
3. To learn to make observations, record data, control variables, and make predictions.
4. To use physical properties and visible chemical reactions to classify substances.
5. To observe some factors that affect the rate of a chemical reaction.
6. To observe, record, and graph experimental data.
Introduction:
When you think of chemistry, what comes to mind? Is it chemists in white lab coats mixing chemicals
with unpronounceable names? Do you think of atoms and molecules, elements and compounds, and
balanced chemical formulas? Chemistry should mean more than just scientific terminology. Chemistry
is the study of the physical and chemical properties of matter, many of which elementary school students
can competently understand through experimentation, by making a science unit emphasizing process
skills, descriptive and applied.
Evidence for a Chemical Reaction: In the first part of this lab, you will see how one knows whether or
not a chemical reaction has occurred? Sometimes a very dramatic occurrence such as an explosion,
makes it clear that there has been a chemical change. Other times, the signs are subtler. There are
however some general outward indicators that provide evidence for a chemical reaction. These include
one or more of the following: formation of a gas, formation of a precipitate, a color change, release or
uptake of heat energy. A chemical reaction that takes energy from its surroundings (gets cold) is called
endothermic. A chemical reaction that releases heat energy to the surroundings (gets hot) is called
exothermic.
In the second part of this lab, you will investigate the properties of common white powders, such a
cornstarch, baking soda, and plaster of Paris, making observations and using indicators and tests much
as chemists do. You will identify an unknown white powder.
In the third part of this lab, you will observe the effects of temperature, concentration, and particle size
on the rate of a chemical reaction.
Part A: Chemical Reactions: The Main Attraction
As you know, everything in the world is made of chemicals and all chemicals are made up of tiny
particles called atoms. A chemical reaction happens when atoms join together or break apart to form
different combinations of atoms. All the atoms are still there they are just connected together in different
ways. Generally the products of reactions have very different properties from the materials we start out
with.
43
1.
Liquids to lumps! Scientists get clues that a chemical reaction may have happened when two or
more liquids are added together and a solid is produced. This solid is called a precipitate.
Procedure:
Half fill your 250 ml beaker with warm water and add super washing soda 1 teaspoon at a time and stir
gently until no more will dissolve. Place 2 tablespoons of warm water into a 100 ml beaker and add
Epsom salts, 1 tablespoon at a time and stir, until no more will dissolve. Add 3 drops of blue food color
to the Epsom salt cup and stir. Use a dropper to pick up some of the blue Epsom salt solution and put
the end of the dropper into the washing soda solution and squeeze gently. Look from the side so you
can see the Epsom salts solution going into the washing soda solution. What do you observe?
Washing soda is sodium carbonate (Na2CO3) and Epsom salts is magnesium sulfate (MgSO4). Complete
the following chemical equation for the reaction you just observed (Hint: the metal ions swap partners):
Na2CO3(aq) + MgSO4(aq) →
2.
Heat up to some cool reactions! A change in temperature is another tip-off that a chemical
reaction may be going on. In some chemical reactions the temperature goes up and in others the
temperature goes down.
Procedure:
1. Record your results in the chart below:
Time (sec.)
Temp (°C)
0
10
20
30
40
50
60
70
80
90
100
2. Pour 2 tablespoons of hydrogen peroxide into a beaker. Add 1 tablespoon of water. Place the
thermometer into the beaker and put the beaker in the lid of your lab box. Hold the thermometer so
the beaker does not fall over. Read the temperature and record it in the chart under "Time 0".
3. Measure out 1 teaspoon of yeast. Have one partner watch the thermometer and the other look at the
second hand on a watch.
4. Dump all the yeast into the beaker. Gently swirl the beaker while one partner calls out the time
every 10 seconds. When each 10 seconds is called, record the temperature in the chart. What do
you observe?
5. Hydrogen peroxide will keep for years in your bathroom cabinet but decomposes rapidly when a
catalyst such as yeast is added. Catalysts speed up reactions but are not consumed in the process.
Hydrogen peroxide decomposes to water and oxygen. Insert appropriate coefficients to balance the
chemical equation for the decomposition of hydrogen peroxide.
44
Temperature (°C)
6. Use the information in your chart to make a line graph of your results. Be sure to divide your x and y
axes so as to clearly show how the temperature changes as the reaction proceeds. (Your scales do not
have to include zero)
Time (sec)
During what period of time did the temperature change the most?
How about the least?
Is this reaction exothermic or endothermic?
7. Record your results for the second experiment in the chart below:
Time (sec.)
Temp (°C)
0
3
6
9
12
15
18
21
24
27
30
8. Place 2 tablespoons of vinegar in a beaker. Put the thermometer in the beaker. Hold the
thermometer and the beaker so they do not fall over. Read the temperature and record it in the chart
under "Time 0".
9. Measure 1 teaspoon of baking soda. Dump all the baking soda in the beaker. Gently swirl the
beaker while one partner calls out the time every 3 seconds. When each 3 seconds is called another
partner should record the temperature in the chart. What did you observe?
45
10. Vinegar and baking soda react together to produce carbon dioxide gas.
Temperature (°C)
11. Use the information in your chart to prepare a line graph of your results.
Time (sec)
12. During what period of time did the temperature change the most?
13. How about the least?
14. Is this reaction exothermic or endothermic?
46
Part B: The Case of the Mystery Powder
Forensic scientists use chemical properties and reactions to help solve crimes. Take, for example, the
case of the Mystery Powder. A series of break-ins had occurred in one neighborhood. In each case, the
investigating officer had noticed a white residue at the crime scene. Based on other evidence, the
officers had four main suspects in the case. When each of the suspects' homes and work places were
examined, it was discovered that each had access to one or more white powders that might have been
accidentally dispersed at the crime scene.
•
•
•
•
Suspect Number 1 worked in a donut shop, where he may have inadvertently picked up baking soda
or cornstarch on his clothes, which then fell off during the break ins.
Suspect Number 2 had several wet (not yet hardened) Plaster of Paris casts in his home.
Suspect Number 3 was a school teacher who often (according to coworkers) left the school with
spots of chalk dusk on his clothes.
Suspect Number 4 had recently spread boric acid throughout his house to combat ants, and
frequently soaked in tubs of Epsom salts to combat his arthritis.
The investigators gathered the powder from the crime scene, then ran a series of physical and chemical
tests on the powder. By comparing these tests to the known results for each of the six powders that may
have been spread by the suspects, they were able to pinpoint the most likely of the four suspects. When
confronted with the results of the Mystery Powder tests, the guilty suspect confessed to the break-ins.
Procedure:
The following simple chemical tests provide valuable clues to distinguish between materials and to
determine some of their properties. Apply the tests to each of the seven powders listed in the following
table including the evidence, an unknown powder, (it will be one of the six you tested). Identify the
evidence. For each test (except the dissolving test), make an indentation in a small pile (1/4
teaspoon) of the powder and place the drop(s) of liquid in the indentation. If possible, use distilled
water to ensure purity in the tests that call for water. For each test, indicate the result with RX if a
reaction (gas formation, color change) or other change occurs, or NR if there is no reaction. Be sure to
include other descriptors that indicate more about what happened, such as a color change, gas
bubbles, etc.
Water test: A drop or two of water on a small amount of the dry powder provides much information to
help differentiate between substance. Does the water soak right in, or does it bead up and roll off? Are
gas bubbles produced? If so, the powder may contain acid and base that react with each other in the
presence of water.
Dissolving test: A little water in a test tube can be used to determine whether certain powders float or
sink when dropped on the water and whether they dissolve in water. (Only use a little solid).
Iodine test: A drop or two of tincture of iodine mixed with water can indicate the presence of starch.
Iodine changes to purple or black immediately when added to cornstarch. What other materials contain
starch? For this test, it helps to put a drop of water on the solid first to moisten it.
47
Vinegar Test: Distilled vinegar is a common, safe classroom acid. Mixing vinegar with baking soda
produces gas bubbles, so dropping vinegar on the test powders is a good way of identifying baking soda
(really a test for carbonate, CO32-). Be sure to observe carefully for any evidence of bubble
formation.
Bicarbonate Test: Adding an aqueous solution of baking soda (a tablespoon of NaHCO3 in 100 mL
water) to an unknown compound is a test for acids. How? Put a drop the baking soda solution on
powders you think are acids. If they are acidic, fizzing will occur due to carbon dioxide gas production.
Look carefully, the bubbles may be small and may also not form rapidly!
Tests
Powders
Water
(behavior)
Dissolving
(solubility)
Iodine
(starch)
Vinegar
(carbonate)
Baking Soda
Boric acid
Chalk Dust
Corn Starch
Epsom Salts
Plaster of Paris
Evidence
Evidence Unknown (A, B, C, or D)_____________________
Identity of the Unknown ____________________________________
Criminal must be Suspect Number ________________
Listed below are other substances that could be tested by these procedures.
Artificial Sweeteners
Talcum Powder
Baking Powder
Biscuit Mix
Dishwashing Powder
Meat Tenderizer
Instant Mashed Potatoes
Flour
48
Cleanser
Cake Mix
Powdered Bleach
Gelatin
Bicarbonate
(acid)
Part C: Effects of Temperature, Concentration, and Particle Size, on the Rates of Reactions:
Kinetics of the Alka-Seltzer Reaction
Introduction:
Effervescent alkalizing tablets (Alka-Seltzer or equivalent) are a relatively inexpensive and safe means
of studying the effects of temperature, concentration and particle size on the rates of reactions. These
tablets contain heat-treated sodium bicarbonate, citric acid, and a salicylate analgesic (aspirin or aspirinlike compound). As long as the tablets remain in the foil–sealed packets, no reaction occurs. By placing
the tablets in water, the following neutralization reaction happens.
3NaHCO3 + H3C6H5O7 → Na3C6H5O7 + 3CO2 + 3H2O
Sodium citrate (Na3C6H5O7, a salt), additional water and copious amounts of carbon dioxide are
formed. A property of this reaction is its effervescence, the rapid release of gas from solution.
Stability of Tablets: (To do at home)
What happens if you take a tablet out of its packet and expose it to the atmospheric water. Take one
tablet out of a packet and place it on a shelf for a week or two. For even faster results, place a tablet in a
refrigerator where the humidity is fairly high. As a control, keep another tablet in a sealed packet in the
same location. You will find the tablet exposed to the moisture in the air has a much slower reaction
rate. This activity will demonstrate the importance of water (solvent) in activating many reactions that
we study in chemistry. For consumer science students, the importance of effective packaging for certain
products is demonstrated.
Temperature and Rate of Reaction:
This experiment will dramatically show the effects of temperature on the rates of reactions. Place three
plastic beakers on the lab bench. In the first beaker, add 60 mL of ice water. To the second, add 60 mL
of water at room temperature (RT), and in the third beaker add 60 mL of hot water. Before performing
the experiment, speculate which reaction will occur fastest. Record the temperature of the water, then
drop a tablet in the beaker. Record the time it takes for the reaction to come to completion (no more
bubbles forming). Graph the results as a line graph. You will need to decide how to divide the X and Y
axes.
Data Table I
Temp °C
Time
_______
_______
_______
_______
_______
Time (sec)
_______
Temperature (°C)
What is the relationship between temperature and the speed of the reaction?
49
Concentration and Rate of Reaction:
For Alka-Seltzer to react it must be dissolved in water. The rate of reaction is highly dependent on the
concentration (percentage) of water in the liquid to which the tablet is added. Place three plastic beakers
on the lab bench. In the first beaker place 60 mL of room temperature water (100% water). In the
second pour 60 mL of rubbing alcohol (70% isopropanol, 30% water). In the third pour 30 mL of
rubbing alcohol and 30 mL of water (35% isopropanol, 65% water). Drop 1 Alka-Seltzer tablet into
each of the 3 beakers and record the reaction times and make a line graph of the results.
% Water
Time
_______
_______
_______
_______
_______
_______
Time (sec)
Data Table II
% Water
What is the relationship between water concentration and the speed of the reaction?
Particle Size and Rate of Reaction:
Place four plastic beakers on the lab bench. Take one alkalizing tablet and grind it to a very fine powder
using a mortar and pestle. Take a second tablet and grind it to the consistency of coarse sand. Take a
third and break it up into 8-12 pieces. Take a fourth and break it up into 4 pieces. For the last sample
(whole), use data from Data Table I (RT). Drop the prepared tablets into each of 4 beakers and add 60
mL of distilled water to each. Record the reaction time and make a bar graph of the results.
Data Table III
Time
1) Powder
_______
2) Small
_______
3) Medium
_______
4) Large
_______
5) Whole
_______
Time (sec)
Piece Size
1)
2)
3)
What is the relationship between particle size and the speed of the reaction?
50
4)
5)
Name
Lab Section
Experiment 9
Getting a Head on Acid Basics
Experiment Objectives:
1. To gain experience in making and recording experimental observations.
2. To learn about the acidity and basicity of common household chemicals.
3. To understand the role of an indicator in acid/base chemistry.
4. To understand the operation of a buffer in controlling pH.
5. To learn that successful science relies more on skills and knowledge than on tools, by conducting
experiments without sophisticated lab equipment
Part I: Cabbage Juice as a pH Indicator
Introduction:
While pH may not be fully understood by students in elementary school, it won't be unfamiliar.
Commercial advertisements constantly refer to pH, especially in cosmetics and over-the-counter drugs.
Swimming pools are tested for pH, and aquariums need a pH specific to the fish. A pH scale is a lot like
the Richter scale for earthquakes, in that each number represents a tenfold change in intensity. Red
cabbage juice is going to indicate, with colored reactions, the pH scale of household chemicals; such as
aspirin and cornstarch. A solution having a pH of 7 is said to be neutral, one with a pH less than 7 is
acidic, and one with a pH greater than 7 is basic (alkaline). Your students will be comparing and
ranking colors, as well as discovering the cause and effects of chemical reactions. They will be
measuring liquids and recording results.
Procedures: Boiling Cabbage Down:
The chemistry is based on the water the cabbage is boiled in. Take about one cup of shredded red
cabbage and boil it in two cups of water for five minutes in a non aluminum pan. The cabbage turns the
water purple. Add two tablespoons of rubbing alcohol to the water as a preservative. If the cabbage
water changes from purple to pink, throw that batch away. The pink indicates bacteria. Refrigerate any
portion you don't use immediately. It also can be stored frozen. You now have what is called a
universal indicator. It undergoes dramatic color changes when combined with such things as lemon
juice, white vinegar and ammonia. The colors created when other liquids are added to the cabbage juice
indicate the liquids acidic or alkaline (basic) levels. (DO NOT DRINK THE CABBAGE JUICE).
Experimental Procedures:
After you have prepared the cabbage juice, test it with the standard pH solutions. Do this by mixing one
dropper full (~1 mL) of cabbage indicator with 10 droppers (~10 mL) of the individual pH solution. Use
colored pencils or crayons to prepare the color chart below. A colored-in copy of this chart is available
at http://chem.csusb.edu/~dpedersn/C304/C304_cabbage_juice_pHchart.html.
pH
1
2
3
4
5
6
7
51
8
9
10
11
12
Using Cabbage Juice Indicator:
Make five (or more) solutions from the samples listed below. For the solids, dissolve only enough solid
to slightly cloud the water. For the liquids mix 4 droppers (~4 mL) with an equal volume of water.
Pour each solution into a test tube and label. These may be labeled with letters of the alphabet if you
wish the students to treat them as "unknowns" (See Experiment 8). Use the colored pH chart prepared by
each student to measure against the results.
Samples: All purpose cleaner; household ammonia; baking soda; washing soda; antacid; soap; hydrogen
peroxide; aspirin; white vinegar.
To fill in the data table below, (1) Predict the color change. Write Pink (acid), or Green (base), etc; (2)
Mix one dropper full (~1 mL) of cabbage indicator with 2 droppers (~2 mL) of the solution to be tested.
Gently swirl the two solutions together. The resulting colors should be brilliant and eye-catching.
Measuring should be consistent throughout this experiment to insure that the indicator colors are similar.
As the students group the resulting colors according to the pH scale, they discover that a solution's smell
and texture are not gauges for its acidic value.
Data Table I
substance tested
prediction:
acid or base?
Observation:
color with
cabbage juice
actual pH: by
comparing to
standards
conclusion:
acid, base, or
neutral
Indicator paper:
Place the excess cabbage juice in a small beaker and dip strips of coffee filter into the juice. Remove the
paper and store them in a dry place. To use the red cabbage test paper, place a drop of the solution to be
tested on the cabbage paper. Compare the color of the test paper with the calibration chart you made in
the first activity.
What do you observe?
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Part II: Red cabbage juice can also be used to find out something about gases. In this activity, you will
find out if a sample of your breath and a sample of gas from a bottle of vinegar and baking soda can
affect the pH of a solution. Note: Your cabbage juice must be purple (fresh) not pink (decayed) for this
to work.
1. Prepare 3 test tubes each by mixing 1 mL of cabbage juice indicator with 4 mL of tap water. Your
indicator should be lavender in color. Put one test tube aside as a control.
2. In an Erlenmeyer flask, place one tablespoon of baking soda. Into a balloon, pour 20 mL of vinegar
and then attach the end of the balloon to the mouth of the flask. After the balloon is attached, pour
the vinegar from the balloon into the flask and collect the gas that forms. After the balloon no longer
inflates and while it is still attached to the flask, twist the balloon so that when you remove it no gas
will escape.
3. Remove the balloon and put the balloon opening around the end of a straw. Now pinch the balloon
opening tightly against the straw and put the other end of the straw into the second indicator liquid.
4. Slowly untwist the balloon so that the gas goes through the straw and into your indicator solution.
Compare the color of the test tube with the color of the control. What conclusion can you draw?
5. Pour the third indicator solution into a small, clean beaker. Using a straw, blow gently through the
third indicator solution for about 1 minute. Return the solution to the test tube. Compare the color in
this test tube with the other two test tubes. Can you see any difference between them?
What conclusion can you draw?
Part III : Is your shampoo pH Balanced? Hair is an acidic substance. Bleach is basic. The
combination of an acid and base is called a neutralization reaction. The material produced by a
neutralization reaction are totally different from the acid and base that were mixed. Bleach can dissolve
any fiber that has acidic properties. Bleach is safe to use on cotton because cotton is basic, but it will
dissolve acidic wool. Highly basic (high pH) or strongly acidic (low pH) shampoos would damage the
hair. This is why most shampoos have pH values between 5 and 8, close to neutral or slightly acidic. A
pH balanced shampoo is important for good hair care.
You will need : piece of hair, bleach, beaker, teaspoon.
1. Fill the beaker one-fourth full with bleach.
2. Collect a small sample of hair and place it in the bleach. Use a spoon to push the hair down into the
bleach so that all the fibers become wet.
3. Allow the beaker to set undisturbed for 20 minutes. What do you observe?
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Part IV Acid Rain and other indicators: BTB
Bromothymol blue (BTB), available at swimming pool stores, has completely different color
characteristics in acidic and in basic solutions. Test water (neutral), vinegar (acidic), and ammonia
cleaner (basic) and record the colors that BTB turns in each.
BTB in water:
(color)
BTB in vinegar:
(color)
BTB in ammonia:
(color)
When organic compounds are burned, CO2 and SO2 are some of the products. When CO2 reacts with
water, carbonic acid (H2CO3) forms. That's why rain water is slightly acidic. When it rains, the raindrops
react with the carbon dioxide to form weak carbonic acid. Write a chemical reaction to show this.
CO2(g) + H2O(l) 
When sulfur is an impurity in gasoline or coal, SO2 and SO3 can form. Since both of these compounds
are also gases, when it rains, raindrops will react with them to form sulfurous and sulfuric acid.
Complete the following chemical reactions to show this.
SO2(g) + H2O(l) 
SO3(g) + H2O(l) 
To see how acid rain forms, perform the following experiment. Add 2 mL of tap water and 2 drops of
bromothymol blue to each of two test tubes. Light a wooden match and quickly insert it into one of the
test tubes. (Do not let go of the match.) After the flame has gone out, remove the match, put your thumb
over the opening of the test tube and shake it up and down. Make sure you get lots of smoke to dissolve
in the water. Repeat with a second match in the same tube. Shake the other tube in a similar manner.
Remember the colors recorded for acids and bases with BTB above. What do you observe?
Does this show how acid rain is formed?
What is the purpose of the test tube with just water in it?
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Part V: Soak up the Acid
Addition of an alkalizing tablet to water results in the formation of a citric acid/sodium citrate mixture.
This mixture acts both as an antacid, to neutralize excess acid in the stomach, and as a buffer. Buffers
are chemicals in a solution that make the degree of acidity (pH) resistant to change when acid or base is
added.
3NaHCO3 + H3C6H5O7 -----------------> Na3C6H5O7 + 3CO2 + 3H2O
Alkalizing Tablets as Antacids:
How do alkalizing tablets work as an antacid? Try the following experiment to find out. To a beaker of
60 mL of tap water add 20 drops of bromothymol blue. Add household white vinegar dropwise until
the color just turns yellow. Mix the solution thoroughly after adding each drop. (This should
require 4-6 drops.) Pour half of the solution into a second beaker. Now add one Alka-Seltzer tablet to
one beaker. After the tablet has reacted completely, let the solution stand for 1-2 minutes, swirling it
occasionally. Compare the color of the solutions in the two beakers. What do you observe?
The reaction alters the pH of the system from acidic to neutral. How do you know?
Alkalizing Tablets as Buffers:
How do alkalizing tablets work as a buffer? Try the following experiment to find out. Transfer 6 mL of
a NEW Alka-Seltzer solution (made from 60 mL of distilled water and an Alka-Seltzer tablet) into a test
tube and add 3 drops of bromothymol blue. Measure 6 mL of distilled water into a second test tube and
add 3 drops of BTB. Now, add enough household ammonia until the Alka-Seltzer solution just turns
blue (2-6 drops should do it; count the drops). Mix the solution thoroughly after adding each drop.
Add the same number of drops to the distilled water. You should have two blue solutions.
Add vinegar (weak acid) to each of the two test tubes one drop at a time (mixing the solution after each
addition) until the solution is acidic (yellow). How many drops of acid were required to make each
solution acidic?
Alka-Seltzer solution: ________drops.
Distilled water: ________drops.
Explain the difference in the number of drops required to turn the Alka-Seltzer solution yellow
compared to the water.
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Name
Lab Section
Experiment 10
Biochemistry
Experimental Objectives:
1. To gain experience in making and recording experimental observations.
2. To observe some of the major similarities and differences between animal fat and vegetable fat.
3. To detect the presence and relative concentrations of starch.
4. To investigate the two main functions of proteins.
5. To isolate and observe the biomolecule, DNA.
Introduction:
Your body is an incredible chemical factory. It is also a living machine that can do many different kinds
of jobs. To stay in good condition it needs many specific chemical compounds, and it manufactures
most of them in an exquisitely organized network of chemical production lines. Your body is made up
of about 100 trillion tiny cells, and thousands of chemical reactions take place within each of those cells
every minute of every day. The study of these reactions and the chemicals they produce is called
biochemistry.
Fats, carbohydrates, and proteins are the three main nutrients in the food we eat. Vitamins and minerals
are also important, but in this lab we will focus on fats, carbohydrates, and proteins. Fats have a bad
reputation because eating too much fat can be harmful to the body. The fats people eat can come from
either plants or animals. Fats from plants and animals are similar in some ways but different in others.
Animal fats tend to be saturated and vegetable fats tend to be unsaturated. The saturation of a fat has to
do with the chemical structure of the fat. The difference in chemical structure causes saturated fats
generally to be more solid at room temperature and unsaturated fats generally tend to be more liquid.
Along with their differences, animal and vegetable fats have several similarities such as being less dense
than water and not mixing well with water. Fats are useful in the body for storing energy, as a
component of cell membranes, and as insulation for the body.
Starch is one of several different types of carbohydrates. It is one of the most popular carbohydrates in
the world. Starch is the major ingredient in bread, potatoes, rice, and pasta. Another major
carbohydrate is sugar in the form of fructose (fruit sugar), lactose (milk sugar), and sucrose (table
sugar). Starch is composed of many molecules of the sugar glucose connected to one another in a
particular way.
Proteins have several functions. They can provide structure like cartilage or act as catalysts called
enzymes. Enzymes help the body's chemical reactions take place by helping to form or break apart
molecules in the body.
Part A: Get the Facts on Fats! (for you to try with your students)
Procedure:
1. Use masking tape to label three zip lock bags water, butter, and oil. Pour hot tap water into your
600 ml beaker until it is about half full. Place about 1 tablespoon of butter, vegetable oil, and water
into the appropriate bags and make sure they are sealed.
2. Place all three bags into the hot water until the butter becomes liquid.
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3. Place a piece of brown paper bag flat on your work surface. Use a pencil to divide the paper into
three sections. Label the sections water, butter, and oil.
4. Dip a separate cotton swab into the liquid in each bag and place the wet end of the swab on its
labeled area on the paper. Reseal the bags and put them back in the water.
5. Tape a piece of wax paper flat on a piece of newspaper. Use separate straws to place a drop of water,
a drop of oil, and a drop of butter on the wax paper. Observe each drop for similarities and
differences. Try dragging each drop along the paper with the straws. What do you observe?
6. Again on your wax paper, use a straw to try mixing a few drops of oil with a few drops of water. Try
the same thing with butter and water. How well did they mix?
Now try mixing some oil and butter. Did they mix any better?
7. Pour cold tap water into a large beaker until it is about 1/4 filled. Pour about 1/2 the butter and about
1/2 the oil from their bags into separate small plastic cups. Place the cups in the cold water and hold
them there so they do not spill. What do you notice happening to either the butter or the oil?
8. Let's look back at your brown paper bag. Do you see any similarities or differences in the way the
liquids look on the brown paper?
Do the butter and oil marks look similar, or does either one look like the water?
9. Fill 2 paper cups about 2/3 full of tap water. Pour the rest of the oil into one cup and the rest of the
butter into the other cup. What did you observe about each liquid?
How are they similar or different?
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Part B: Starch Search!
Procedure:
1. On a sheet of white paper, label three areas as follows: cracker, rice, and pasta. Place a small
amount of each food on its area of the paper.
2. Place 1 drop of diluted tincture of iodine on each type of food. What do you observe?
A dark color shows you that the iodine has reacted with starch in the food. Do all these foods seem to
contain starch?
The iodine test can tell us whether a food contains starch. Let's see whether another kind of iodine
test can tell us if one food sample has more or less starch than another.
3. Use your masking tape and pen to label 4 - 100 ml beakers, 1, 2, 3, and 4. Break a cracker into 4
equal-sized pieces. Place one piece in each of your four labeled beakers. Add 1 tablespoon of water
to beaker 1, 2 tablespoons of water to beaker 2, 3 tablespoons of water to beaker 3, and 4 tablespoons
of water to beaker 4.
4. Use separate straws to stir and mix your crackers with the water in each beaker until the cracker has
completely fallen apart and is well mixed with the water.
5. Use a straw to take a few drops from the top of each water/cracker solution. Place 3 drops of each
solution on a piece of wax paper. Rinse the straw with water between uses.
6. Add 1 drop of iodine to the drops of each solution on the wax paper. Did the color change in any of
the solutions?
Did all the colors look the same?
What explains the difference in the color if you saw any?
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Part C: Proteins: Your Pro Team!
As you read earlier, proteins can be separated according their purpose. The first purpose we will
investigate is structure. In the following activity, you can experiment with the protein that makes up
cartilage and tendons.
Procedure:
1. Place 1 tablespoon of Knox unflavored gelatin into a cup. Add two teaspoons of water while mixing
rapidly with a straw. Continue stirring until the gelatin mixture is well mixed and thick enough to
scoop out with your fingers.
2. Scoop out the gelatin mixture and knead it back and forth between your hands. (Put a little water on
your hands so the gelatin will not stick to your hands too much.) Form the gelatin into a ball. Allow
the gelatin ball to sit for about 2-3 minutes. Save this gelatin ball for the next part as well.
3. Gently squeeze the ball of gelatin. What does it feel like?
When you press it, does it go back to its original shape?
Gelatin is made from a protein called collagen. Collagen is the main protein that makes up your
body's cartilage and tendons!
4. The outside of your ear is mostly cartilage. Gently bend your ear and let it go. Are there any
similarities between your ear and the gelatin ball?
Gently push the tip of your nose to the side and let go. Do you think there is cartilage in your nose?
5. How about tendons? Sit in a chair with your feet flat on the floor. Bend down and feel the thick cord
behind your ankle. This is your Achilles tendon. Gently press it with your fingers. How does it
compare with your gelatin ball?
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A second purpose of proteins is to help your body's chemical reactions take place by helping to form
or break apart molecules in the body. Proteins that have this special function are called enzymes. In
the activity below, you can test the enzyme in meat tenderizer to see whether it will affect the proteins
in gelatin.
6. Use your pen and masking tape to label a beaker tenderizer. Mark two areas on your paper as
tenderizer and water. Place 1 tablespoon of gelatin into the beaker.
7. Add 2 teaspoons of water and 1/4 teaspoon of meat tenderizer to the gelatin in the tenderizer beaker
and stir rapidly. Continue stirring until the gelatin mixture is well mixed and thick enough to pick up.
8. Scoop out enough gelatin mixture to knead it back and forth between your hands. Form the gelatin
into a ball. Allow the ball to sit for 2-3 minutes and place it on the area of the paper labeled
tenderizer.
9. Retrieve the gelatin ball you made in the first part of this experiment (step 2) and put it onto the area
of the paper labeled water.
10. Compare the tenderizer ball and the water ball by gently squeezing each one. Do you notice any
difference between them?
What do you think the tenderizer has done to the proteins in the gelatin?
How do you think tenderizer makes meat tender?
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Part D: More on enzymes
I. Chemical reactions in your mouth
Procedure:
1. Cut two small pieces from a slice about one-inch square from a piece of white bread.
2. Place one piece in your mouth and chew it about 30 times until it becomes very mushy. Make an
effort to mix as much saliva as possible with the bread.
3. Spit the mushy bread and saliva mixture onto a piece of waxed paper.
4. Place the second dry piece of bread onto a separate piece of waxed paper and moisten the bread with
a few drops of water.
5. Add 2 drops of iodine to both bread pieces.
What do your observe?
What is happening to the starch in the bread as it mixes with saliva?
II. Breakdown
Procedure:
1. Fill 2 test tubes one-half full with hydrogen peroxide and observe the solution. Look specifically for
bubbles of gas.
2. Add a few slivers of raw potato to one of the test tubes.
3. Observe the results. What difference if any, do you see?
Raw potatoes contain the enzyme catalase. Catalase from the potato's cells causes the hydrogen
peroxide to quickly break apart into water and oxygen gas.
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Part E: Isolation of DNA from onion - “Snot on a Stick”
Complex compounds called nucleic acids are found in every living cell. They serve as the information
and control centers of the cell. There are actually two kinds of nucleic acids. Deoxyribonucleic acid
(DNA) is found primarily in the cell nucleus. Ribonucleic acid (RNA) is found in all parts of the cell.
Both nucleic acids are made of long polymers of repeating units called nucleotides. An important
feature of the nucleic acid molecule is the sequence of the nucleotides along the chain. This is a crucial
feature of these molecules, because it is the sequence that is used to store the multitude of information
needed to build living organisms. DNA contains the information necessary to make all the proteins
needed by a cell.
This activity is designed to show how DNA can easily be extracted from onion cells. A slightly
different approach is described at the following web site:
http://gslc.genetics.utah.edu/basic/howto/index.html
The solutions are already prepared; go straight to student directions.
Materials/Group:
cm2 pieces of fresh onion
100 ml beaker
2 test tubes
Q-tip
ice cold 95% ethanol
Dawn liquid detergent
non-iodized salt (sodium chloride)
fresh meat tenderizer or fresh pineapple or papaya juice
phenol red indicator solution
Teacher's guide for preparation of materials:
1. Prepare the detergent/salt solution by adding 10 ml of Dawn liquid detergent and 10 grams of salt to
90 ml of distilled water. This solution breaks down the cell membranes to release the contents of the
cell which includes the DNA.
2. Prepare a 5% meat tenderizer or papain solution by adding 5 grams of tenderizer (enzyme) to 95 ml
of distilled water. The juice of pineapple or papaya may be substituted for the tenderizer. The
enzymes will breakdown (denature) proteins that may contaminate the DNA.
3. The 95% ethanol must be ICE COLD. It should be left in a plastic container in the freezer overnight.
4. Prepare a 5% sodium chloride solution by adding 5 grams of non-iodized salt to 100 ml distilled
water.
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Student directions:
1. Dice an onion to give about 5 teaspoons and transfer the diced onion to a mortar and pestle. Add
one teaspoon of sand and grind vigorously for 3 minutes. (Alternately, this can be done with a larger
amount in a blender. Use low speed for 45 seconds.)
2. Transfer the mush from the mortar to a 100 mL beaker containing 30 mL of the detergent/salt
solution and stir this mixture for 5 minutes.
3. Transfer only the liquid to a new 100 mL beaker by filtering the mixture through a coffee filter or
through cheesecloth. Try to obtain as much of this yellow liquid as possible as it contains the DNA.
Add 3 to 4 ml of the meat tenderizer/enzyme solution to the DNA solution. Swirl the beaker to mix.
4. Carefully pour 30 ml of ice cold ethanol down the side of the beaker to form a layer on top of the
onion mixture. Let stand for 3 minutes.
5. Without disturbing the two layers, slowly move the wooden end of a Q-tip using a twirling motion
through the interface of the two layers to collect the mucus-like DNA (called spooling) on the rod.
Once you have spooled enough DNA to see, describe your DNA.
Now you can place the rod with the spooled DNA in a clean test tube with 2 ml of the 5% salt
solution. Add 1 drop of the indicator phenol red to the DNA solution. Phenol red turns yellow in
acidic solutions. What do you observe?
What do you think would make the indicator change color?
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Name
Lab Section
CHEMISTRY 304
HOMEWORK LABORATORY #1
PART I: Title: How can an egg float? (a density experiment)
Purpose: To determine the effect of density of a solution on floating.
Materials: egg, large glass or other suitable container, tablespoon, salt, water.
Procedures:1) Place an egg in the glass. 2) Add 200 ml of water to the glass with the egg in it.
Observe whether the egg floats or not. 3) Add salt to the glass, one tablespoon at a time, while stirring.
Observe the effect on the egg. Do not use “free range” eggs (non-supermarket eggs).
Observations:
Conclusion:
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PART II: Title: The Cartesian Diver
Purpose: To determine if the pressure exerted on an object can affect its density.
Materials: 1 or 2-Liter clear, plastic soda bottle with cap. Transfer pipette (obtain from instructor),
screw ( medium to large), water.
Procedure: Using scissors, cut approximately 1 inch off the stem of the pipette. Attach the screw to
the bottom of the pipette. Adjust the water level in the pipette such that it just floats in a glass of water.
This is the “Diver”. Rinse out the plastic bottle and remove the label. Fill the bottle with water to
within 2 cm of the top. Insert the “Diver” and screw the cap on securely. Squeeze the bottle and
observe the diver descend. Relax the squeeze and watch it ascend. Try to squeeze the bottle just hard
enough so that the diver is suspended mid-way down the bottle. Watch the water level in the pipette
bulb, and think about the compressibilities of gas and of liquid.
Describe what happens to your diver.
Offer explanations for what you have observed (remember: gas laws and density).
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Name
Lab Section
CHEMISTRY 304
HOMEWORK LABORATORY #2
PART I: Title: Incredible Growing and Shrinking Egg (an experiment in chemical reactions and
osmosis)
Purpose: To observe the effects of vinegar, and later Karo syrup on an egg .
Materials: 1 raw egg, a glass, vinegar, Karo syrup
Note: this experiment requires at least a week to complete
Procedure:
1. Place the egg in a transparent glass container that is somewhat larger than the egg. Cover the egg
with vinegar. Observe the egg after a few minutes, after an hour, after a day, after 4 days. Leave the
egg in the vinegar for at least 4 days before proceeding with part 2.
2. After 4-7 days pour off the vinegar, and examine the egg's "shell", consistency, and size. Add
enough Karo syrup to the glass to completely cover the egg. (Alternatively, one can use a
concentrated sugar solution prepared by dissolving 26 tablespoons of table sugar in one cup of
water.) Wait at least 3 more days, and again observe the egg, particularly noting its size and color.
Background:
Supplemental material available on the Web: (http://dbhs.wvusd.k12.ca.us/ColligProp/Osmosis.html,,
http://www.howstuffworks.com/question29.htm). Vinegar is composed of 5% acetic acid (HC2H3O2),
that reacts with (and dissolves) carbonates to give off CO2 (remember the mystery powder lab, and test
for carbonates). Egg shells are composed primarily of calcium carbonate, CaCO3. Once the shell is
removed, vinegar can also penetrate the semi-permeable membrane that is just under the shell. Vinegar
has the effect of "pickling" or denaturing the protein in the egg, much the way heat does during boiling.
Water can also penetrate the semi-permeable membrane surrounding the egg, once the shell is removed.
There is a high concentration of water in vinegar (5% acetic acid and 95% water), and a much lower
concentration of water in Karo syrup (supersaturated solution of sugar in water). There is an
intermediate concentration of water within a raw egg. Osmosis occurs when water (or some small
molecule or ion) can penetrate a barrier, while other substances present in the system cannot. Osmosis
occurs in order to "balance" the concentrations of water and other substances in a system. Osmosis is the
basis of many processes in living systems.
Observations: (be sure to include these at various time periods after addition of the vinegar, and after
addition of the Karo syrup)
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Observations (continued)
What evidence do you have that a chemical reaction has taken place between the egg shell (CaCO3) and
the vinegar (HC2H3O2)? (Look back at Experiment #8 for ideas of what indicates that a chemical
reaction has occurred.)
Conclusions?: Why did the shell of the egg change? Why did the size of the egg change in vinegar? In
Karo syrup?
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PART II: Title: Growing Crystals
Purpose: To create a saturated solution, and allow slow crystal growth; to
examine the structure of the crystals as a function of crystal growth rate
Materials: table salt or Epsom salts, a glass, hot water, a spoon, string, a pencil, a paper clip, black
paper
Note: this experiment requires at least a week to complete
Procedures:
Saturate 200 mL solution of hot water in a drinking glass or cup , with either table salt (NaCl) or Epsom
salts (MgSO4) (that is, add salt one teaspoon of the salt at a time to about 1 cup of very hot water, until
no more will dissolve). After the solution has cooled, pour it into a clean drinking glass, taking care not
to transfer any solid lying on the bottom. Tie a paper clip to a piece of string, and suspend the paper clip
in the solution (but not touching the bottom of the glass). Balance a pencil across the top of the glass,
and tie the string to it. Set the glass in a quiet location for 1-2 weeks without disturbing it. Remove the
string from the solution to examine the crystals formed.
Write down the substance that you used (Epsom salts or table salt). Describe what you see. How does
the new solid compare to the original crystals used to make the solution (It may help to place the
original crystals and the new ones side by side on a piece of black construction paper)? What is
happened to the water level, and to the solid as it crystallizes?
Observations:
What is happening in the solution as the crystals form?
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