Elementary Core Science Units
Physical Properties—Grade 1
Learning Experience 4
The Temperature Is Rising
Description
Students learn how heat can vary from one extreme to the other, how heat can be
measured, and what occurs when waters of different temperatures are mixed.
Time Frame
2 lessons (30 minutes each)
Materials
16-oz. foam cups (3 per group)
Permanent marker
A way to heat water (hotplate, microwave, coffee maker)
Water
Thermometers with no markings, attached to white plastic or waterproof paper
(2 per student group)
Red crayons or colored pencils (1 per student)
How Hot? ordering mat with three spaces for placing objects (included in the
blackline masters)
Science journals
Correlations to the Science TEKS
During this activity, students will be exposed to the following grade 1 science
concepts from the Texas Essential Knowledge and Skills:
(1.7) Science concepts. The student knows that many types of change occur. The
student is expected to:
(A)
observe, measure, and record changes in size, mass, color,
position, quantity, sound, and movement;
(B)
identify and test ways that heat may cause change such as when ice
melts;
Advance Preparation
1. Prepare three cups of water for each group.
With a permanent marker, label the cups A, B, and C. In cup A, put cold
water. In cup B, put hot water. In cup C, put room-temperature water. If you
use tap water for the room-temperature water, it needs to sit overnight in
order for the temperature to stabilize.
Fill the cups only halfway.
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Elementary Core Science Units
Physical Properties—Grade 1
2. If the thermometers are not attached to a white waterproof card, use bread
ties to attach each thermometer to a card backing. Use a red permanent
marker and make a mark where the liquid in the thermometer is stable (room
temperature). From that mark, make a black tick mark every half-centimeter
above and below this first mark. Students in grade 1 do not work with
standard units. When they describe the temperature change, they should say
that it is x marks above or below the red mark.
3. Copy the How Hot? ordering mat for each student and laminate it for future
use. For this experience, students will need the mat that has three spaces for
placing objects.
Procedures
1. Let the students know that today they will be exploring how to measure
change of heat.
2. Divide students into groups and give each group its three cups of water.
3. Tell the students to find a way to figure out how to order the cups of water
based on how hot the water in each one is. However, tell them that they may
not touch the water. Have the students as a class develop a method—which
will involve students touching the outside of the cups—and record it on the
board or chart paper.
4. Have the groups use the How Hot? ordering mat to order the cups of water
from coldest to hottest. Once the students are done, check their answers.
They should have answered A, C, B.
5. Next, tell the students that they will be mixing some of the cups of water to
observe what happens. Ask students what will happen if they add half of the
water of cup B (hot water) to cup C (room temperature). Have the students
discuss what they think will happen to the temperature of the water, and then
let them pour the water.
6. After the students have poured the water, have them feel cup C. Ask, “Is cup
C hotter or colder now? What happened to Cup C? Why do you think it is
hotter?”
7. Have students pour the rest of cup B (hot water) into cup A (cold water). Ask
students to feel cups A and C and decide whether they can tell which one is
warmer.
They should be close to the same temperature, leading the students to realize
that they may need another way to measure the temperature than by sense of
touch.
8. Ask students if there is a better way to find the temperature than just
describing it as hot or cold. Ask them how they think scientists measure
whether something is cold or hot.
Help students come to the conclusion that they can use something called a
thermometer to measure temperature.
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Elementary Core Science Units
Physical Properties—Grade 1
Ask the students where they might have seen a thermometer at home.
[On the oven in the kitchen; on the water heater; hanging outside a window.]
Show them an unmarked thermometer and tell them how the red liquid in the
thermometer rises when the thermometer is placed in hot water and lowers
when placed in cold water. Demonstrate this by putting one unmarked
thermometer in a cup of hot water and one in a cup of cold water.
9. Give each student group two thermometers and guide them in taking the
temperature of cups A and C. On the Measuring with a Thermometer page in
their journals, have students mark their measurements on the thermometer
pictures and color in the red liquid. Ask them to reorder the cups on their
ordering mats from coldest to hottest.
10. Have the students discuss which of the two methods (using their hands and
using a thermometer) was more accurate and safer.
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Elementary Core Science Units
© 2007 Charles A. Dana Center at The University of Texas at Austin
Measuring with a Thermometer
Color in the thermometers to show which cup has hotter
water.
Cup A
Elementary Core Science Units
Cup C
© 2007 Charles A. Dana Center at The University of Texas at Austin
Elementary Core Science Units
Physical Properties—Grade 4
Learning Experience 1
As a Matter of Fact
Description
Students recall what they learned in third grade about the properties of solids,
liquids, and gases and are introduced to the concept that states of matter exist
because of the amounts of energy in the particles of the substance.
Time Frame
1 lesson (45 minutes)
Materials
Jars with lids (3)
Pencil
500 mL of water
Vanilla extract
Red, green, and blue construction paper (2 sheets each)
Science journals
Correlations to the Science TEKS
During this activity, students will be exposed to the following grade 4 science
concepts from the Texas Essential Knowledge and Skills:
(4.7) Science concepts. The student knows that matter has physical properties.
The student is expected to:
(A)
observe and record changes in the states of matter caused by the
addition or reduction of heat; and
(B)
conduct tests, compare data, and draw conclusions about physical
properties of matter including states of matter, conduction, density,
and buoyancy.
Advance Preparation
1. Place a pencil in one jar and affix the lid. Place 500 mL of water in a second
jar and affix the lid. Place a drop of vanilla extract in the third jar, affix the
lid, and agitate it so that there appears to be only air in the jar.
2. Cut the construction paper into quarters. On the red rectangles, write “Solid.”
On the green rectangles, write “Liquid.” On the blue rectangles, write “Gas.”
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Elementary Core Science Units
Physical Properties—Grade 4
Procedures
1. Show students the three jars with lids. Ask, “Which is a solid?” [The pencil.]
“A liquid?” [The water.] A gas? [The air in the third jar.]
2. What do you notice about the shape of the contents in each jar?
[The solid pencil keeps its own shape. The liquid water takes the shape of the
jar it is in, filling the bottom part of the jar. The gaseous air spreads out in
its jar, filling the entire jar.]
What would happen to the shape of the contents if we remove the lids?
[The solid pencil would retain its shape. The liquid water would continue to
have the shape of the bottom part of the jar. The gaseous air would flow into
the room, mixing with the air in the room, while some of the air in the room
might mix with the air in the jar.]
3. Tell students that the reason that states of matter exist—the reason we have
solids, liquids, and gases—is because the particles in different substances
have different amounts of energy.
To give students a perspective on different amounts of energy, refer to how
the particles move in liquids, solids, and gases. Particles move very slowly in
solids, a little faster in liquids, and very quickly in gases.
4. Remove the jar lids. Ask students this question: “If the particles of the solid
(the pencil) stay in the jar when the lid is removed, the particles of the liquid
(water) stay in the jar when the lid is removed, and the particles of the gas
(scented air) leave the jar when the lid is removed, what can we say about the
gas?”
Note: Students were formally introduced to states of matter in third grade but
have not related the energy in the particles to the states of matter. This activity
does not highlight the energy of the particles but has students consider the
movement of the particles in different states of matter.
[Possible student responses: The gas floated out; the gas moved faster or
more than the pencil and water.]
5. Have several students represent the particles of a solid by holding the red
rectangles marked “Solid” and standing closely together, jiggling a little to
represent the movement in the particles of a solid.
6. Have a different group of students hold the green rectangles marked “Liquid”
and stand in a marked spot on the floor (such as a tile edge or a crack). Tell
students to move around but not to leave that area. Mention that students can
gently bump into each other as they move around.
7. Finally, have a third group of students hold the blue rectangles marked “Gas”
and tell the students to move freely around the room.
8. Using the three jars from earlier in the activity, ask the following questions:
What did we observe about the three groups?
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Elementary Core Science Units
Physical Properties—Grade 4
[They all move differently.]
Relate the groups’ movement to the three jars. Which group represented Jar
A? [solid] Which group represented Jar B? [liquid] Which group represented
Jar C? [gas]
9. In their journals, have students draw and label a model of the particles of a
solid, liquid, and gas.
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Middle School Core Science Units
Chemical and Physical Properties—Grade Seven Module
LEARNING EXPERIENCE 3
Element Sort
Description:
During this learning experience, students will examine how physical properties
are used to organize elements on the periodic table.
Time Frame:
2 lessons (45 minutes each)
Materials:
Periodic table (1 per student)
Colored pencils (1 set per student group)
A Short History of Nearly Everything (book)
Element Sort teacher key (included in the blackline masters section for this
learning experience)
Element Sort data cards (included in the blackline masters section for this
learning experience)
Element Sort blank data cards (included in the blackline masters section for this
learning experience)
Resources:
Bill Bryson. A Short History of Nearly Everything. New York: Broadway Books,
2003, pages 106–109.
Sources:
Mark Winter. “WebElements™ Periodic Table Scholar Edition.”
www.webelements.com/webelements/properties/text/image-flash/hardnessmineral.html. (Date retrieved: December 18, 2005.) Copyright 1993–2004,
Dr. Mark J. Winter, The University of Sheffield and WebElements LTD, UK.
Advance Preparation:
1. Make a copy for each student of pages 106–109 from A Short History of
Nearly Everything.
2. Prepare a set of Element Sort data cards for each student group by
photocopying the cards on heavy-weight paper or cardstock. Separate the
cards by cutting along the dark lines. Remove ONE card from each set for
use as an assessment (the same card should be removed from each student
group’s set). Shuffle the cards in each set before distributing to the students.
Note: You may want to remove a different card for each class to avoid students
from other classes knowing the answer.
3. Prepare a blank data card for each student group.
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Note: The Element Sort teacher key in the blackline masters is for teacher use
only.
Procedures:
Setting the Stage
Note: NO periodic tables are to be viewed or accessible during this part of the
learning experience.
1. Review the definition of physical property learned from elementary science
classes.
2. Give a set of Element Sort data cards to each student group. Have the
students spend a moment looking at the data listed on the cards.
3. Review the information on the cards with the students. Students should be
familiar with some of the element names after looking at the periodic table in
the previous learning experience. Answer all questions students have about
the data on the cards EXCEPT those questions referring to the mystery
symbol in the upper left corner of each card.
4. Distribute a copy of the reading selection from A Short History of Nearly
Everything to each student. Have half the class read pages 106–107, starting
with “Despite . . .” on page 106; have the other half of the class read pages
108–109, starting with “For most of us . . .” on page 108 and ending with
“scheme” on page 109.
5. On chart paper or the chalkboard, record student responses to the following
questions:
a. Why is it called the periodic table?
b. How many elements were on Mendeleev’s periodic table?
c. Why was it beneficial to group elements by more than one property?
d. Is Mendeleev the true developer of the periodic table? Explain your
answer.
Student Investigation
6. Have each student group use the information on the Element Sort data cards
to “group” and then organize the cards into a “table.”
7. Distribute periodic tables to the students. Have students use the periodic table
and the table their group created in the previous step to identify the patterns
for the physical properties.
8. Guide students as they use the colored pencils to color the patterns of the
elements. On the board or on chart paper, develop a universal key (for
example, “color all metals blue”). Using the properties identified on the
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Middle School Core Science Units
Chemical and Physical Properties—Grade Seven Module
Element Sort data cards, continue through each of the identified physical
properties.
9. Tell students that one card was removed from each set of data cards. Give
each student group ONE blank data card and have the students place it where
the missing card should go. For example, if you removed the Fluorine card
prior to distributing the data cards to the student groups, then the students
should place the blank card between Oxygen and Neon.
On the blank card, have each group predict the properties and/or range of
properties for the element on the missing card. From the patterns identified,
students should be able to predict some of the element’s physical properties
(for example, gas, colorless, density between 1.25–1.7 g/cm3, mass between
14–19 g, etc.). Then, give each group a copy of the missing card so the group
can compare its predictions with the data on the actual card.
Note: The design of the mystery symbol in the upper left hand corner of each
card is based on the metallic properties of the element. The vertical side of the
triangle is the same across a period, but increases down the group representing
the different periods on the table. The horizontal side of the triangle is the same
down each group, but decreases across the groups.
10. After identifying the missing card, students should be able to identify the
pattern found on the periodic table for each of the physical properties listed
below:
a. Phase
b. Metallic nature
c. Color
d. Density
e. Boiling point
f.
Mass
g. Formation of compounds (The mathematics TEKS state that students
may use ratios.)
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Middle School Core Science Units
Chemical and Physical Properties—Grade Seven Module
Blackline Masters
for
Element Sort
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Middle School Core Science Units
Chemical and Physical Properties—Grade Seven Module
Element Sort Teacher Key
STP is “Standard Temperature and Pressure
(273 K and 1 atm)”
Metal
Non-metal
Metalloid
Phase at STP:
Solid =
Liquid =
Gas =
Element Sort Data Cards begin on the next page. There are five pages of Element Sort Data Cards, and
they are followed by one page with Element Sort Blank Data Cards.
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Middle School Core Science Units
Chemical and Physical Properties—Grade Seven Module
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Middle School Core Science Units
Chemical and Physical Properties—Grade Seven Module
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Middle School Core Science Units
Chemical and Physical Properties—Grade Seven Module
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Middle School Core Science Units
Chemical and Physical Properties—Grade Seven Module
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Middle School Core Science Units
Chemical and Physical Properties—Grade Seven Module
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Middle School Core Science Units
Chemical and Physical Properties—Grade Seven Module
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Integrating High School Science
Module 2: Properties and Patterns
LEARNING ACTIVITY 7
Atomic Multitudes
Purpose
To relate the solubility and viscosity of fluids to the kinetic theory.
Time Frame
1 lesson (55 minutes)
Materials
Note: All the materials listed will be used by the teacher during teacher
demonstrations.
Demonstration #1
600 mL beakers (6)
250 mL of sugar
250 mL of water
50 marbles
Tray
Demonstration #2
Magnetic water molecules kit
Demonstration #3
1 test tube filled with pancake syrup (the inexpensive kind is fine)
1 test tube filled with corn syrup or molasses
1 test tube filled with water
Tray
Demonstration #4
4 test tubes filled with corn syrup or molasses
1 test tube filled with pancake syrup (the inexpensive kind is fine)
1 test tube filled with water
Ice bath
Warm water bath
3 marbles
Tray
Demonstration #5
500 mL beakers (2)
800 mL of water
400 mL of vegetable oil
400 mL of ethanol or isopropyl
1 bottle of food coloring
Magnetic water molecules kit
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Module 2: Properties and Patterns
Demonstration #6
250 mL beaker filled with salt
250 mL beaker filled with sugar
2 beakers, each containing 300 mL of water
2 spoons
Stopwatch
2 stirring rods
Magnetic water molecules kit
Hotplate
Demonstration #7
1 unopened bottle of clear soda
3 unopened plastic bottles of clear soda (16–20 oz., with label removed)
Ice water bath
Room temperature water bath
Hot water bath
Background Information for the Teacher
This learning activity consists of several teacher demonstrations. Following each
demonstration, there will be a teacher-led discussion that uses questioning
strategies to guide students to the appropriate conclusions.
As part of each demonstration/discussion, the teacher will:
•
demonstrate a phenomena,
•
have students carefully observe the phenomena and record their findings,
•
ask students how the kinetic theory (or atomic hypothesis) could possibly
explain the observed behavior,
•
provide an atomic-level picture that explains what is happening on the
macroscopic level, and
•
ask students to explain the macroscopic behavior in terms of the motion
and interactions of atoms and molecules.
Advance Preparation
You may wish to set up each demonstration on a separate tray to assist in
materials management. If more than one instructor is available, have each
instructor carry out the learning activity with a group of students.
Procedures
1. Read the following quote to students:
American physicist and educator Richard Feynman once said that if he had to
condense all of science into one paragraph, “The most important information
. . . is the atomic hypothesis . . . that all things are made of atoms—little
particles that move around in perpetual motion, attracting each other when
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Module 2: Properties and Patterns
they are a little distance apart, but repelling upon being squeezed into one
another.”
Ask students to relate the quote to things they have learned from this module.
[Possible student responses include the conservation of mass, the creation of
compounds from elements, the different types of bonding, and the behavior of
ionic compounds.]
Demonstration #1
2. Place the following items in separate 600 mL beakers: approximately 50
marbles, 250 mL of sugar, and 250 mL of water. Pour the contents of each
beaker into a separate empty 600 mL beaker, and ask students to observe
what happens.
Have students, as a class, discuss the similarities and differences between the
behaviors of the substances. Include the following points during the
discussion:
•
All three substances can be “poured” since they are made up of many
individual particles. The water is made up of water molecules, which are
too small to be seen but are still individual “things.”
•
All three substances take the shape of their containers.
•
Water is “soft,” the marbles are “hard,” and the sugar is somewhere in
between. Emphasize that an individual water molecule is actually very
hard, but since there are millions of tiny water molecules in a glass of
water, they tend to “flow” around objects. Thus, water seems less
substantial than the marbles or sugar. Remind students how painful it is
to “belly flop” into a swimming pool.
Next, carefully pour some of the water onto a flat surface. The water should
bead up. On a different flat surface, pour out some of the marbles. The
marbles should roll about randomly.
Have students discuss the similarities and differences between the behavior
of the water and the marbles.
[The water molecules seem to attract each other while the marbles do not.]
Ask students to relate their observations to the atomic hypothesis.
Specifically, ask them to explain the ways in which their observations of the
marbles, sugar, and water support the atomic theory. Guide students to the
following conclusions:
•
According to the atomic hypothesis, everything is composed of atoms
(and molecules), which 1) are constantly in motion, 2) attract each other
when far away, and 3) repel each other when very close. Water shows
this behavior since its molecules move about easily (flow), attract each
other (the “beading” behavior), and repel each other (two water jets will
not pass through each other undisturbed).
•
The marbles do not seem to attract each other. However, they do repel
each other, i.e., they are unable to pass through one another. Each marble
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Module 2: Properties and Patterns
is composed of millions of atoms. Because the atoms on the surface of
marbles repel each other, the marbles bounce when they collide.
Although the force of attraction between separate marbles is very weak,
the force of attraction between the atoms within a marble is very strong.
In fact, the intermolecular forces are so strong; they make the marble
seem hard as a rock.
•
Although sugar is composed of individual molecules, we cannot see the
molecules. When we look at sugar, we see a crystal—a regular collection
of molecules held together by intermolecular forces. When sugar
dissolves, the crystals break up into individual molecules. However,
since the individual molecules are too small to see, sugar seems to
disappear when dissolved in water.
Demonstration #2
3. Use the magnetic water molecules kit to demonstrate how water molecules
both attract and repel each other.
Emphasize to students that at cold temperatures, water molecules don’t move
very fast (they have low kinetic energy), so the intermolecular forces
“freeze” the water and form ice. When water molecules are moving faster,
liquid water forms because the intermolecular forces are unable to hold the
molecules in place. However, even in the liquid state, individual water
molecules still “stick” to each other, causing water droplets to bead up. At
high temperatures, when the water molecules are moving very fast (they have
high kinetic energy), the intermolecular forces are unable to keep the water
molecules together and the water changes into steam. Emphasize that all
three forms of water (ice, liquid water, and steam) are composed of identical
water molecules. The only difference is how successful the force of attraction
is at making the water molecules’ neighbors “stay put.”
Pose the following question: Why does steam cause a more severe burn than
boiling water?
[Because more energy is required to break intermolecular forces. Therefore,
the molecules are moving much faster than in boiling water. That energy
transfer causes more damage to tissue.]
Demonstration #3
4. Place the following items in separate test tubes: water, pancake syrup, and
corn syrup or molasses. Using a shallow slope, set up a downhill “liquid
race” (see diagram). Have students observe the results of the race.
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Have students working in groups create a table showing the results of their
observations. Also, have students use their fingers to compare the “feel” of
all three liquids, and then record their results in the table. (A sample table is
provided.)
Sample Table
Liquid Race
Observations
Water
Pancake
Syrup
Corn Syrup /
Molasses
Movement Speed
Moves fastest
Moves at medium
speed
Moves slowest
Texture
Feels like water
Feels “thicker”
than water
Feels very “thick”
Explain to students that “viscosity” is the word used by scientists to describe
how easily a liquid flows. Viscosity depends on the molecular forces
between individual molecules as well as the molecule’s shape and size.
Based on the test performed, ask the students to predict the size of the
molecules in the substances used. [The molecules of syrups (sugars) are
much larger than the water molecules.]
If you have the bottles of the products available, have the students check the
ingredients. They will find that the pancake syrup contains water whereas the
molasses does not.
Demonstration #4
5. Before conducting this demonstration, ask students to predict what will
happen to a fluid’s viscosity if its temperature increases. Students should
justify their answers based on the atomic theory and the motion of the
molecules.
[As the temperature increases, the molecules move faster. This makes it
harder for the intermolecular forces between the molecules to restrict the
motion of the molecules. Thus, increased temperature should make the
material less viscous.]
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6. Place corn syrup/molasses in three test tubes. Cool one test tube in an ice
bath and heat another test tube in a warm water bath. (Caution: Do not heat
the corn syrup/molasses directly over a flame or hotplate.) Keep the third test
tube at room temperature.
Run a new downhill race with the three test tubes. Have students working in
groups create a table to record their observations of the race. Also, have
students use their fingers to compare the “feel” of all three liquids, and then
record their results in the table. (A sample table is provided.)
Sample Table
Liquid Race
Observations
Cold
Corn Syrup /
Molasses
Room Temperature
Corn Syrup /
Molasses
Hot
Corn Syrup /
Molasses
Movement Speed
Moves slowest
Moves at medium
speed
Moves fastest
Texture
Feels very “thick”
Feels normal
Feels very “thin”
7. Relate the results from this demonstration to motor oils. Tell students that
motor oil’s viscosity helps it “stick” to moving parts in an automobile engine.
Ask students to explain why running an engine at high speed is more likely
to damage it than running it at low speed.
[At high speeds, an engine produces a lot of heat. This heat makes the engine
oil less viscous, so it doesn’t stick to the engine parts as well. This
“thinness” increases the likelihood of damage. Because small engines and
small cars run at cooler temperatures, they can use “light oil,” whereas
large and less well-designed cars tend to use “heavy oil.” Note: A diesel
engine uses diesel fuel as both a fuel and a lubricant. This is possible
because diesel fuel is more viscous than gasoline.
8. Reinforce the importance of viscosity by dropping a marble into a test tube
filled with water, a test tube filled with corn syrup/molasses, and a test tube
filled with pancake syrup. Have students discuss the differences in viscosity.
Demonstration #5
9. In this demonstration, the atomic theory is used to help students understand
what happens when two liquids are mixed.
Put 300 mL of colored water into a 600 mL beaker. Pour 100 mL of
vegetable oil into the same beaker. Two distinct layers will form.
Have students explain the observed behavior in terms of the atomic theory.
[The oil and water molecules are more attracted to their own type of
molecule: oil to oil and water to water.]
10. Tell students that the ability of two liquids to mix depends on the properties
of both substances. In all cases, the substance being dissolved is called the
solute, and the substance “doing the dissolving” is called the solvent.
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Students just observed an attempt to dissolve oil (the solute) into water (the
solvent). Next, students will see if the behavior of oil and water when
dissolved depends upon which substance is the solute and which is the
solvent.
11. Put 300 mL of vegetable oil into a 600 mL beaker. Pour 100 mL of colored
water into the beaker. After a few minutes, the water and vegetable oil will
separate. Ask students to describe what they observed.
Write the formulas for water and vegetable oil on the board:
H2 O
C30H56O6 (small lipid molecule)
Water
Vegetable Oil
Ask students to compare these two molecules for similarities and differences.
[Water is a small molecule; oil is a very large molecule. If you pour some oil
on a smooth surface, it doesn’t bead up. Therefore, it doesn’t behave like
water.]
12. Now, students will look at what happens when water and alcohol are mixed.
Write the formulas for water, ethane, and ethanol on the board:
H2 O
C2H6
C2H5 OH
Water
Ethane
Ethanol
Ask students to compare these molecules for similarities and differences.
[Students should notice that both substances are small molecules. Use the
magnetic water molecules kit to show why ethanol will dissolve, but ethane
(C2 H6) will not.]
13. Ask students to predict what will happen when ethanol and water are mixed.
Students should justify their predictions.
[Since water and ethanol both are polar molecules, they should mix well.
Note: This is a serious oversimplification of the actual behavior of liquids,
but it does give students the opportunity to discover the “like dissolves like”
rule through directed inquiry.]
14. Test student predictions by adding 100 mL of colored water to 300 mL of
alcohol, and 100 mL of alcohol to 300 mL of colored water. Make sure
students understand the “like dissolves like” generalization.
Demonstration #6
Note: During this demonstration make sure to use the words solute (sugar or salt)
and solvent (water). Students tend to have a hard time with these terms, so it is
important to model their use and to have the students use the terms as they
explain the phenomena they observe.
15. In this demonstration, students will look at how solids dissolve in liquids.
Show students two beakers: one full of salt and one full of sugar. Write the
formulas for sugar and salt on the board.
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Integrating High School Science
Module 2: Properties and Patterns
C12H22O11
NaCl
Sugar
Salt
Ask students what types of bonds are present in sugar and salt. [Sugar is
covalent, and salt is ionic.]
How do they use the periodic table to help determine the bond type? [Sugar
is comprised of non-metallic elements; salt is comprised of a metallic and a
non-metallic element.]
Predict which solute will dissolve better in water (the solvent) and to justify
their predictions.
[Student answers will vary. Encourage students to justify their predictions
based upon the kinetic theory (atoms in motion), “like dissolves like,” or the
behavior of ionic compounds.]
16. Have two pairs of students assist you with the following demonstration.
Assign each pair the responsibility of dissolving one of the solutes in 300 mL
of water in the following manner: One student adds 1 spoonful of the solute
every five seconds; the other student stirs the solute/solvent mixture. Have
the class observe and record what happens.
[Both salt and sugar will dissolve in water, but the amount of sugar dissolved
is much greater. In fact, as you add more and more sugar, you will
eventually get a syrupy mess.]
17. Use the magnetic water molecules kit to show students how water molecules
+
can surround and hydrate the dissociated Na and Cl ions. Write the
+
equation for the disassociation of salt on the board (NaCl ⇒ Na + Cl ).
Emphasize to students that because it takes many water molecules to dissolve
a single salt ion, the solubility of salt is limited.
Ask students if there is anything that we can do (based on the atomic theory)
to get more salt to dissolve in water.
[Heating the water causes its water molecules to move faster. These rapidly
moving molecules are more effective in suspending the Na+ and Cl- ions.
Because each ion must be surrounded, very little salt goes into solution
compared to the sugar, even with heating.]
Verify the effect of heat on solubility by heating 300 mL of water to near
boiling and dissolving as much salt as possible in the water.
18. Explain to students that when solids dissolve in water, the water molecules
must be able to “get at” the solid, surround it, and suspend the solute
molecules. Ask students, “Based on this understanding, would you expect
granulated sugar or a sugar cube to dissolve more rapidly?”
[Student answers will vary. Record student predictions and test. The
granulated sugar should dissolve faster.]
Ask students why some “fast acting” medicines come in powdered form
rather than tablet form.
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Integrating High School Science
Module 2: Properties and Patterns
[The smaller particle size in the powdered medicine helps it dissolve faster.
Note: This concept will be revisited in the next module.]
Demonstration #7
19. Open a clear bottle of soda. Ask students to observe what happens and record
their observations.
[Bubbles appear and rise to the surface.]
Tell students that the bubbles are carbon dioxide that was dissolved in water.
Ask students what changed to limit the solubility of the carbon dioxide gas.
[The pressure decreased.]
20. Remind students that there are gases dissolved in our blood. Ask students
which gases? [oxygen, carbon dioxide] The air we breathe is about 21%
oxygen, so the gas in scuba tank is also a mixture of oxygen, nitrogen,
hydrogen, and an inert gas like neon. Ask students, “What would happen to a
deep-sea diver who suddenly surfaced?”
[The presence of gas bubbles in the blood stream results in a painful and
possibly fatal disease called “the bends.” Since the pressure decreases, the
solubility of the gases decreases and bubbles form in the bloodstream.]
21. Ask students to use the atomic theory to predict what will happen when a
bottle of soda is heated.
[As the temperature increases, the carbon dioxide molecules in the soda
move faster and are able to “break away” from the attractive forces of the
soda “molecules.” Therefore, the solubility of a gas decreases as the
temperature increases.]
Demonstrate this concept by submerging a bottle of soda in an ice water
bath, a room temperature water bath, and a very hot water bath. After a few
minutes, CAREFULLY open all the bottles. The bottle of soda in the hot
bath should visibly release more carbon dioxide.
Performance Assessment
22. Assign each of the following topics to a different student group.
•
The viscosity of a fluid decreases as the temperature increases.
•
Water and oil do not mix.
•
Sugar dissolves in water better than salt dissolves in water.
•
Increased pressure increases gas solubility.
•
High temperature increases the solubility of solids.
Have each group create a poster to explain their assigned phenomena. The
poster must include:
•
a drawing that shows the interactions between atoms and molecules
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Integrating High School Science
•
a graph of the relationship being explained
•
a real-world example of the phenomena
Module 2: Properties and Patterns
23. Have each group present their poster to the class and answer any teacher or
student questions.
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