Inner Space

Inner Space
Learning Objectives: Investigate the properties of molecules,
and discuss the use of models in science.
GRADE LEVEL
2–8
SCIENCE TOPICS
Atoms and Molecules
Techniques
PROCESS SKILLS
Predicting
Making Models
Explaining
GROUP SIZE
3–4
SNEAK PEAK inside …
ACTIVITY
Students completely fill cups with marbles or
water. Then they discover that there is still room
to add salt or sand between the marbles or
water molecules.
STUDENT SUPPLIES
see next page for more supplies
plastic cups
marbles
salt
sand
cafeteria trays, etc….
ADVANCE PREPARATION
see next page for more details
Fill water containers.
Prepare cups of marbles, sand, and salt.
etc….
OPTIONAL EXTRAS
DEMONSTRATION
Odors Aloft (p. A - 38)
EXTENSIONS
Inquiry Opportunity (p. A - 43)
Density of Saltwater and Plain Water (p. A - 43)
TIME REQUIRED
Advance Preparation
Set Up
Activity
Clean Up
5 minutes
10 minutes
20 minutes
10 minutes
Inner Space
Grades 2–8
A - 35
Chemistry in the K–8 Classroom
2007, OMSI
SUPPLIES
Item
Amount Needed
plastic cups, 8-oz. or smaller
5 per group
water
1 cup per group
pop-top squeeze bottles (e.g., water or sport drink)
16 oz. or larger
1 per group
marbles (or other small, spherical objects)
1 cup per group
large jar or margarine tub, 2- to 4-cup capacity
1 per 2–3 groups
salt
½ cup per group
sand
½ cup per group
plastic spoons
OR
measuring teaspoons
2 per group
cafeteria trays
1 per group
coffee filters
several for class to share
strainer
1 or more for class to share
bowl
1 or more for class to share
For Extension or Demonstration supplies, see the corresponding section.
ADVANCE PREPARATION
Supplies Preparation
Water:
Fill pop-top squeeze bottles with about 1 cup of water.
‰ Label bottles with “water.”
Marbles:
‰ Fill large jars or margarine tubs with marbles.
‰ If marbles are unavailable, buttons or large rounded rocks
could work.
‰ Spherical objects are best since they leave the most empty
space in the cup.
Sand:
‰ Fill plastic cups with about ½ cup of sand.
‰ Label cups with “sand.”
Salt:
‰ Fill plastic cups with about ½ cup of salt.
‰ Label cups with “salt.”
‰
Inner Space
Grades 2–8
A - 36
Chemistry in the K–8 Classroom
2007, OMSI
Notes and Hints
‰ It does not matter whether you use plastic spoons or
measuring spoons for this activity. However, to compare
results between groups, it is important that all plastic spoons
are the same size.
‰ Cafeteria trays help to contain spilled water in this activity.
SETUP
For each group
pop-top squeeze bottle with water
‰ ½ cup salt in a plastic cup
‰ ½ cup sand in a plastic cup
‰ 3 plastic cups
‰ 1–2 plastic spoons
‰ cafeteria tray
‰
At a central location (or with the teacher)
sponges and towels for clean up
‰ large containers of marbles
‰ coffee filters, strainer, and large bowl or tub.
‰
INTRODUCING THE ACTIVITY
Let the students
speculate before
offering answers to
any questions. The
answers at right are
provided for the
teacher.
Choose questions
that are
appropriate for
your classroom.
Depending on the background knowledge of your students, you
may wish to start with the demonstration and discuss the properties
of molecules.
What are the different states of matter?
Sold, liquid, gas.
How are molecules arranged in all of these states?
In a solid, molecules are packed together in a regular way. They
vibrate in place. In a liquid, molecules are close together, and they
move and jostle one another constantly. In a gas, molecules are
spread far apart and move at high speed.
Notice that in all states of matter, the molecules of a substance
stay together, but there are still spaces between molecules. In this
activity, students will study this inner space between molecules.
Inner Space
Grades 2–8
A - 37
Chemistry in the K–8 Classroom
2007, OMSI
For this activity, we will be filling a cup so that it is full of water. How
shall we decide when the cup is “full”?
Take suggestions from students. As a class, agree to a definition of
what a “full” cup of water looks like. It may be level with the top of
the cup, water added until it is bulging over, or somewhere in
between.
For this activity, we will be counting full spoonfuls of sand and salt.
How shall we measure a “full” spoonful?
Take suggestions from students. As a class, agree to a definition of
what a “full” spoonful looks like. It may be leveled off using a
pencil, or it may be as much as you can pile on, or somewhere in
between.
It is very important that the class agree to a definition of “full” for
both the water in the cup and the sand and salt in the spoon. This
assists in comparing results. Also, and perhaps more importantly,
scientists have standard measures they use, and defining measures
as a class is good scientific practice.
TEACHER DEMONSTRATION
Odors Aloft
As an introduction to the properties of molecules, prepare a
balloon for students to observe using the sense of smell.
This is a small part of the full activity Odors Aloft.
Supplies
‰ 2–3 balloons
‰ peppermint extract (Note: Any extract will work, but
peppermint seems to work best. It is a very recognizable
smell and diffuses through the balloon very quickly.)
‰ straw (for inserting extract into balloon)
How to Insert Extract (Figure 1)
1. Collect some peppermint extract (less than 1 tsp.) with a
straw. Use your finger on the top of the straw to trap the
liquid in the bottom.
2. Insert the straw into the mouth of the balloon.
3. Release the contents into the balloon.
4. Remove the straw.
5. Blow up the balloon and tie it closed. Be careful not to let
the balloon deflate until it is tied closed.
Inner Space
Grades 2–8
A - 38
Chemistry in the K–8 Classroom
2007, OMSI
Figure 1. Steps
to insert extract into a balloon.
Demonstration
‰ In front of the students, insert peppermint extract into a
balloon. (See pictures and instructions above.)
‰ Inflate the balloon and tie it.
‰ Repeat with another 1 or 2 balloons.
‰ Discuss the following with the students:
• Where is the peppermint extract? (It is inside the balloon.)
• Is there a way for it to get out of the balloon? (No, the
balloon holds it inside. Yes, there are small holes in the
balloon surface that we can’t see.)
• How could we find out if any peppermint extract is
escaping? (We would be able to smell it!)
‰ Pass the balloons around the class and invite students to
smell them. Students should be able to smell peppermint
extract through the balloon.
Explanation
We smell odors when the molecules of a substance reach our
nose. Even though the balloon is solid, the molecules in the
peppermint extract were able to pass through the balloon to
our nose. This is because when molecules are together to make
a material, there is still space between the molecules that allow
smaller molecules to pass through.
Inner Space
Grades 2–8
A - 39
Chemistry in the K–8 Classroom
2007, OMSI
CLASSROOM ACTIVITY
Have students follow the Scientific Procedure on page A - 45, working in groups of 3–4.
Below are suggestions to help the teacher facilitate the activity.
NOTES
This handout is
on p. A - 45.
Running Suggestions
‰
‰
‰
‰
Inner Space
Grades 2–8
Students should record their observations as the procedure
prompts them. If a question comes before a step, students
should record their answer BEFORE doing the step.
As described in Introducing the Activity, the class needs to
decide what “full” means when filling their cups with water.
Does full mean level on the top or bulging over so no more
will fit? This activity will work both ways but works best if
students choose full to mean bulging over. Students tend to
fill their cups about the same amount when they all try to
“overfill” them to bulging. Also, very full cups of water fill
more quickly with salt and sand.
Water will spill in this activity. Tell students to do their
experiments on the cafeteria tray.
Tell students to put their sand water and saltwater cups in a
secure place before they add water. Adding so much water
makes the cups impossible to move without spilling.
A - 40
Chemistry in the K–8 Classroom
2007, OMSI
Ongoing Assessment
‰
‰
How do your results compare to your predictions?
Do you think the same thing will happen if you repeat the
experiment? Try it and see.
Safety and Disposal
‰
‰
Students should pour sand water through a coffee filter or
paper towel and strainer to separate the sand. Once the
sand is collected, it can be reused.
Salt water can go down the sink.
Caution: Do not pour sand down the sink. It may clog the drain.
CLASSROOM DISCUSSION
Ask for student
observations and
explanations. Let
the students guide
the discussion and
present their
hypotheses before
discussing
explanations.
Choose questions
that are
appropriate for your
classroom.
Did the experiment turn out as you predicted?
Answers will vary. Most students will be surprised at how many
spoonfuls of salt will fit into the a full cup of water.
How many spoonfuls of sand were you able to add to your cup of
water? How many spoonfuls of salt were you able to add?
Collect information from the students.
Where did the salt go? Why did more salt fit in the water than sand?
Even though the cup appeared “full,” there was still space
between the molecules of water. Both the salt and sand fit in
between these spaces, but the salt fit better because it dissolved in
the water. The salt molecules break up into parts, which fit easily
into the spaces between the water molecules. The sand could not
dissolve, so it could not fit as well into those spaces.
For more information about how salt dissolves in water, see the
Explanation section of Salting Out.
If the marbles represented water molecules, where was the salt fitting?
The salt fit between the water molecules, just like it would fit
between the marbles.
Inner Space
Grades 2–8
A - 41
Chemistry in the K–8 Classroom
2007, OMSI
Are marbles a good representation of molecules? Why or why not?
Yes. Marbles fit together in certain patterns just like molecules fit
together in certain patterns. There is space between marbles just
like there is space between molecules.
No. Marbles leave a lot of space between them and molecules
don’t leave as much space. Marbles are spherical and not all
molecules are spherical. Also, molecules move, and marbles don’t.
EXPLANATION
By adding salt to an already full cup of water, students discovered that it is
possible to fit salt molecules between the molecules of water. This inner space
allowed an already full cup of water to fit more material.
Properties of Matter
All matter is made up of atoms. Atoms bond together to make molecules. Inside
and between molecules and atoms are empty spaces. Molecules are farthest
apart in a gas, but, even in a liquid state, molecules have plenty of space
between them.
Fitting into the Inner Space
Table salt, also called sodium chloride (NaCl), is made up of equal parts of two
small atoms called sodium (Na) and chlorine (Cl). In water, the sodium and
chlorine atoms separate from each other and become surrounded by water
molecules. In this process, the salt dissolves in the water.
The salt fills the spaces between the water molecules. This allows more matter to
fit in the cup even though it is already full of water. This means that when we
compare a full cup of water to a full cup of saltwater, the saltwater will have
more matter in it, and it will weigh more. Because saltwater has more matter in
the same volume when compared to plain water, saltwater is more dense than
plain water.
For a more detailed discussion of density, read the explanation section of Big
Things Come in Little Packages.
Sand, or silica (silicon dioxide), cannot break up to fit into the spaces between
water molecules. Sand does not dissolve in water. For this reason, students cannot
add as many spoonfuls of sand to their full water cups as they can add salt.
Surface Tension of Water
Water molecules have a strong attractive force to one another. This attractive
force, known as surface tension, allows the water to bulge on the top of the cup
before spilling over.
Inner Space
Grades 2–8
A - 42
Chemistry in the K–8 Classroom
2007, OMSI
EXTENSIONS
Extension A: Inquiry Opportunity
Repeat the experiment and substitute different ingredients for the ones used in
the main activity.
‰ Instead of water, try vinegar, rubbing alcohol, or vegetable oil
‰ Instead of salt, try sugar, Epsom salt, or powdered milk
‰ Try changing the temperature of the liquid used in the experiment
CAUTION: Rubbing alcohol (70% isopropyl alcohol) is flammable and poisonous.
Keep away from heat and open flames.
Extension B: Density of Saltwater and Plain Water
Students measure and compare the densities of saltwater and plain water.
Extra Supplies
‰ scale or balance
‰ measuring cups
Extra Instructions
‰ Add salt to ½ cup of water and mix until no more salt will dissolve in the water.
‰ Measure ¼ cup of the saltwater and pour it into a plastic cup.
‰ Weigh the container with the salt water in it. Record the weight of the
container with saltwater.
‰ Empty and dry the plastic cup. Save it for the next step.
‰ Measure ¼ cup of plain water and pour it in the plastic cup.
‰ Weigh the cup with the plain water in it. Record the weight of the
container with plain water.
‰ Which weighs more, the cup with saltwater or the cup with plain water? Why?
Explanation
Even though both the saltwater and the plain water take up the same
amount of space, the saltwater weighs more. This is because the saltwater
has salt dissolved in the water, filling up some of the space between the
water molecules. When two substances take up the same space, but have
different weights, the one that weighs more is more dense.
For a more detailed examination of the comparative densities of liquids, try the
activity Density Rainbow.
Inner Space
Grades 2–8
A - 43
Chemistry in the K–8 Classroom
2007, OMSI
CROSS-CURRICULAR CONNECTIONS
BIOLOGY
Importance of Salt
Discuss how saltwater is necessary for many living things. For example,
human blood is about 1% salt, and the ocean environment is about 3.5%
salt. If the salt content is too high, most living things cannot survive. That is
why salt is used to preserve food and prevent growth of microorganisms
on, e.g., bacon, pickles, etc.
PHYSICS
Surface Tension
Discuss the surface tension that allowed the glass to fill “beyond full”—to
bulge over the top of the glass.
RESOURCES
Web – http://www.middleschoolscience.com/suface.htm
The general website features many science lesson plans. This lesson plan (under Chemistry)
explores the surface tension of water by counting how many drops of water will fit on a penny. The
website address really does have “surface” misspelled.
VOCABULARY
atoms:
a very, very small particle that makes up all matter
dense:
describes how tightly packed molecules are in a substance
dissolve:
when the molecules of a substance separate and become
completely surrounded by the molecules of another
substance
molecules:
a group of at least two atoms held together in a definite
arrangement
silica:
silicon dioxide; forms the mineral quartz, which is the main
ingredient in sand
surface tension:
an elastic-like force in liquids caused by the molecules at the
surface being attracted to one another
Inner Space
Grades 2–8
A - 44
Chemistry in the K–8 Classroom
2007, OMSI
Inner Space
SCIENTIFIC PROCEDURE
1. Label three cups “marbles,” “saltwater,” and “sand water.”
2. Completely fill the cup labeled “marbles” with marbles.
• How do you know the cup is full?
• Do you think you could add sand to this cup? Where would the sand
go if you added it?
3. Add sand to the cup full of marbles.
• How many spoonfuls of sand can you add to the marbles?
• Where did the sand go?
4. Completely fill the cups labeled “saltwater” and “sand water” with water.
• How do you know the cups are full?
• How are these cups full of water similar to the cup full of marbles?
5. In the next step, you will add sand to the “sand water” cup until the water
overflows.
• Predict: How many spoonfuls of sand do you think you can add?
6. Carefully add 1 spoonful of sand to the “sand water” cup. Count
and add more spoonfuls of sand.
• How many spoonfuls of sand could you add to the water?
• Where did the sand go?
7. In the next step, you will add salt to the “saltwater” cup until the water overflows.
• Predict: How many spoonfuls of sand do you think you can add?
8. Now add one tablespoon of salt to the “saltwater” cup. Count
and add more spoonfuls of salt.
• How many spoonfuls of salt could you add to the water?
• Where did the salt go?
9. Clean up your area.
• Follow your teacher’s directions.
SUPPLY WORKSHEET
This worksheet is available online at www.omsi.edu/k8chemistry.
Inner Space
Recommended group size: 3–4
Number of Students:
Supplies
Number of Groups:
Amount Needed
plastic cups, 8-oz. or smaller
5 per group
water
pop-top squeeze bottles (e.g.,
water or sport drink) 16 oz.
marbles (or other small, spherical
objects)
large jar or margarine tub, 2- to 4cup capacity
salt
2 cups per group
sand
plastic spoons
OR
measuring teaspoons
cafeteria trays
coffee filters, strainer, and bowl (or
plastic tub)
½ cup per group
Supplies
on Hand
Supplies
Needed
1 per group
1 cup per group
1 per 2–3 groups
½ cup per group
2 per group
1 per group
1 set for class
Extension A
alternate liquids: vinegar, alcohol,
or vegetable oil
alternate solids: sugar, Epsom salt,
or powdered milk
hot water or cold water
2 cups each liquid per
group
½ cup each solid per group
2 cups each temperature
per group
Extension B
scale or balance
1 or more for class to share
measuring cups
1 set per group
Teacher Demonstration
Odors Aloft
balloons
2–3 per class
peppermint extract
2–3 tsp. per class
straw
1 per class
Inner Space
Grades 2–8
A - 47
Teacher Resource Guide
2007, OMSI
Inner Space
Grades 2–8
A - 48
Teacher Resource Guide
2007, OMSI