Science
Starts With
a Question
Chemical
Reactions
Student Guide
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Science Starts With a Question is a collaboration between the Smithsonian Science Education Center and The
Dow Chemical Company.
About the Smithsonian Institution
The Smithsonian Institution was created by an Act of Congress in 1846 “for the increase and diffusion of
knowledge…” This independent federal establishment is the world’s largest museum and research complex
and is responsible for public and scholarly activities, exhibitions, and research projects nationwide and
overseas. Among the objectives of the Smithsonian is the application of its unique resources to enhance
elementary and secondary education.
About the Smithsonian Science Education Center
The Smithsonian Science Education Center (SSEC) is operated by the Smithsonian Institution to improve the
teaching of science in the nation’s schools. The SSEC disseminates information about exemplary teaching
resources, develops curriculum materials, and conducts outreach programs of leadership development and
technical assistance to help school districts implement inquiry-centered science programs. Its mission is
to transform the teaching and learning of science in a world of unprecedented scientific and technological
change.
Smithsonian Science Education Center staff involved in development of this publication
Katya Vines, PhD
Curriculum Developer
Brian Mandell, PhD
Curriculum Developer
Claudia Campbell, Jean Flanagan, Patti Marohn
Ashley Deese
Elizabeth Klemick Brannan
Taryn White
Editors
Designer
Proofreader
Production Specialist
Marjee Chmiel, PhD
Associate Director for Curriculum
and Communications
Amy D’Amico, PhD
Director of Professional Services
Eric Nastasi, Esq.
Lisa Rogers
Teng Chamchumrus
Senior Advancement Officer
Director of Finance
Interim Director
Teachers involved in development of this publication
David Brown
Science Teacher
Bullock Creek Middle School, Michigan
Scott Harrison
Science Teacher
Freeland Elementary School, Michigan
Science Starts With a Question: Chemical Reactions
i
About The Dow Chemical Company
Dow’s STEM mission is to build the workforce of tomorrow by empowering teachers, motivating student
achievement, developing careers, and collaborating with communities to transform STEM education into a
driver for innovation, manufacturing, and economic prosperity.
To live out this mission, Dow has created STEMtheGAP™— a growing and constantly evolving series of
initiatives to support and advance STEM education. While stakeholders, target audiences, and focuses may
vary, every initiative is designed to inspire conversation about STEM education, collaboration to develop
innovative solutions and, as a result, transformation that will enable our nation and the world to surmount
the challenges of the 21st century.
For more information on Dow’s STEMtheGAP™ initiatives, visit:
http://www.dow.com/company/citizenship/stem.htm
Dow staff involved in development of this publication
Patrick Heider, PhD
Chemical Engineer
Stephanie Hughes
Chemist
Tricia Wilson
Chemical Technologist
Cassie Fhaner, PhD
Chemist
Meagan Zabetian
Supply Chain Analyst
Jaime Curtis-Fisk, PhD
Chemist
®TM Trademark of the Dow Chemical Company (Dow) or an affiliated company of Dow.
©2015 Smithsonian Institution
Image Credits
Cupcake - Rubix_3/iStock/Thinkstock; Mars Gullies - NASA/JPL-Caltech/Arizona State University; Veggie Burger - bhofack2/iStock/
Thinkstock; Gymnast - Petr_Joura/iStock/Thinkstock; Burning Logs - VvoeVale/iStock/Thinkstock; Onion Rings - AndyVernum1/
iStock/Thinkstock; Bubble Tea - sitti_/iStock/Thinkstock; Wikipearls - (C) 2015, WikiFoods Inc.
The illustrations on the cover and chapter opening page are by Tim Bradford.
Science Starts With a Question: Chemical Reactions
ii
How to Use This Guide
Welcome to your Chemical Reactions Student Guide! This Guide contains three lessons
developed by the Smithsonian Science Education Center in partnership with The Dow
Chemical Company. As you work through the lessons, you will be doing the same things that
a real scientist does. You will see that anyone can be a scientist!
The following features in this Guide will help you become a better scientist:
Key Term
These explain new science words and terms.
Did You Know?
Interesting and fun facts relate to the activities you are carrying out.
? Question It
Research these questions to dig a little deeper.
Look It Up
Visit these websites for further reading.
Stay Safe
Science is fun but can also be dangerous. The advice in these boxes will help you stay safe.
Science Starts With a Question: Chemical Reactions
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Science Starts with a Question
Key Term
Chemical
Reactions
Chemical reaction: What
happens when substances
mix to form new substances.
Central Question
Did You Know?
How can I tell if I have made something new?
Dow makes chemicals for
suntan lotion that makes
it easier for you to rub the
lotion into your skin. Some
chemicals are also water
resistant, which helps the
lotion stay on your skin!
Suntan lotion protects your
skin from the Sun’s harmful
rays.
Module Overview
What happens to paper when it burns? Where does the
light come from in a glow stick? In this module, you will
learn about what happens when two substances mix and
combine to form a new substance. You will draw a model
to explain what is going on when baking soda and calcium
chloride are mixed. Then you will use your model to explore
some unusual and fun chemical reactions with a scientist
from The Dow Chemical Company. In the last lesson, you will
refine your model and use it to test a prediction.
Lesson One: Model Development
Lesson Overview
In this lesson, you will find out what happens when baking
soda and calcium chloride mix and draw a model to explain
your observations. Then you will make a prediction based on
your model, which you will test in Lesson 3.
Science Starts With a Question: Chemical Reactions
1
Let’s Get Started
In a physical change, the substance is the same at the
beginning and at the end of the change even though it
might look different. A change in state, such as ice melting, is
a physical change.
1.
What is an example of a physical change?
2.
What happens to the particles in your example?
Reaction of Baking Soda and Calcium Chloride
You will find out what happens when you mix baking soda
and calcium chloride. Carefully observe what happens when
you mix the two compounds. You will work in groups of four
to complete this activity.
? Question It
One use of calcium
chloride is to keep canned
vegetables firm. What other
food and drink is calcium
chloride added to?
Science Starts With a Question: Chemical Reactions
2
Materials
For each student
Safety goggles
Disposable gloves
For each group of four students
2 Beakers (50 mL)
1 Graduated cylinder (25 mL)
1 Thermometer
1 Spatula
Pen or labels
For groups to share
Calcium chloride
Baking soda
Distilled water
Stay Safe
Remember the following laboratory rules for working with
chemicals:
r Dress appropriately for the laboratory. Wear long sleeves and
shoes that completely cover your feet.
r Wear your safety goggles at all times when working with
chemicals.
r Never touch a chemical with your hands unless your teacher or
ambassador tells you it is safe to do so. Use a spatula to handle
chemicals.
r Be careful when touching anything that may be hot or cold.
r If you spill a chemical or break any glass, tell your teacher or
ambassador immediately.
r If you get a chemical on your hand, wash your hands
immediately with soap and water.
r Never taste chemicals.
r When smelling in the laboratory, ”waft” the smell toward you
using your hand.
Science Starts With a Question: Chemical Reactions
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Procedure
Did You Know?
Stay Safe
Thermometers are glass and break easily.
1.
Add a spatula of calcium chloride to one beaker
followed by 25 mL of water. Stir until most of the
calcium chloride dissolves. Label this beaker ”calcium
chloride.”
2.
Add a spatula of baking soda to the second beaker
followed by 25 mL of water. Stir until most of the
baking soda dissolves. Label this beaker ”baking soda.”
3.
Write down the appearance of the two liquids in
question 1 of What Is Going On. These are your starting
materials.
4.
Put the thermometer in the beaker containing calcium
chloride. Wait until the liquid stops moving and take
the temperature.
5.
Slowly add the baking soda to the calcium chloride
and observe what happens.
6.
Write down your observations in question 2 of What Is
Going On.
7.
At the end of the activity, follow your teacher’s
instructions to dispose of the chemicals.
The chemical name for
baking soda is sodium
bicarbonate. Because
sodium bicarbonate occurs
naturally and is non-toxic,
it has a wide range of uses.
The Egyptians used sodium
bicarbonate to make soap.
Science Starts With a Question: Chemical Reactions
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What Is Going On?
1.
What do the starting materials look like? List all the
physical properties of your starting materials.
2.
What do you observe when you mix the two liquids?
Include what happened to the temperature.
3.
What do you think happened to the particles in baking
soda and calcium chloride after they mixed? Draw a
model in the space below. You may include arrows,
images, or any other symbols you think might help
people understand your model.
Science Starts With a Question: Chemical Reactions
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4.
Bakers use baking soda to make cakes and other
baked goods rise and become nice and ”cakey”! Based
on your model, why do you think baking soda causes a
cake to rise?
5.
Based on your model, why do you think that you
dissolved calcium chloride and baking soda in water
first?
6.
In Lesson 3, your teacher will repeat this activity using
a flask with a narrow neck instead of a beaker for
calcium chloride. First, your teacher will put all the
materials on an electronic balance along with a
balloon. Then he or she will add the baking soda
to the flask containing calcium chloride and quickly
add the balloon to the top of the flask. What do you
think will happen to the reading on the electronic
balance? Will it go up, go down, or stay the same?
Explain your reason for your prediction.
Science Starts With a Question: Chemical Reactions
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Review
1.
Key Term
List three signs of a chemical reaction based on your
observations during today’s activity.
Precipitate: A solid that
separates from a liquid
during a chemical reaction.
Science Starts With a Question: Chemical Reactions
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Lesson 2: Model Investigation
Lesson Overview
In this lesson, you will explore the model you developed in
Lesson 1. First, a Dow STEM ambassador will carry out several
short demonstrations. Then you will carry out a series of
activities working in pairs. You will use what you have learned
about chemical reactions to decide whether a chemical
reaction has taken place. Be careful though, because some of
the activities may not be all they seem!
Note
STEM stands for Science, Technology, Engineering, and Math.
There are questions at the end of this lesson about your
ambassador, so make sure you get to know him/her as he/she
helps you with your activities.
Let’s Get Started
Your teacher will introduce the ambassador.
1.
Write down the ambassador’s name.
2.
List all the things that you think a scientist does during
an average working day.
Science Starts With a Question: Chemical Reactions
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Fog Maker
Key Term
The ambassador will drop some dry ice—solid carbon
dioxide—into a graduated cylinder of warm water.
Sublimation: When a solid
heats and changes straight
to a gas.
Stay Safe
Dry ice has a temperature of –78.5°C (–109.3°F) and can cause
frostbite if it touches bare skin. Always wear thick gloves when
holding or touching dry ice.
What Is Going On?
1.
What do the starting materials look like? What do you
observe when they mix? Use your observations to
decide whether a physical change or chemical reaction
has taken place.
Appearance of
starting materials
Observations when
starting materials
were mixed
Physical change or
chemical reaction?
Evidence
Science Starts With a Question: Chemical Reactions
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Crime Scene Investigation
Did You Know?
The ambassador or teacher may dim the lights in the room.
The ambassador will pour luminol—the chemical found in
glow sticks—and household bleach into a funnel at the top of
a spiral tube.
What Is Going On?
1.
What do the starting materials look like? What do you
observe when they mix? Use your observations to
decide whether a physical change or chemical reaction
has taken place.
Appearance of
starting materials
Observations when
starting materials
were mixed
Physical change or
chemical reaction?
Forensic scientists use
luminol to find traces of
blood. If blood is present,
it reacts with the luminol,
which causes the luminol to
glow. However, using bleach
to clean up the blood can
also cause the same reaction.
Evidence
Key Terms
Chemiluminescence: A
chemical reaction that gives
Look It Up
The Smithsonian Ocean Portal has lots of information and pictures of
interesting bioluminescent organisms that live deep in the ocean. Visit
http://www.ssec.si.edu/Dow/Chemical to explore the Ocean Portal.
off light.
Bioluminescence: A
chemical reaction that
gives off light inside a living
organism.
Science Starts With a Question: Chemical Reactions 10
Invisible Shelf
The ambassador will put some dry ice into an empty
aquarium. After a few minutes, he or she will ask a student to
blow bubbles in the aquarium.
What Is Going On?
1.
What do the starting materials look like? What do you
observe when they mix? Use your observations to
decide whether a physical change or chemical reaction
has taken place.
Appearance of
starting materials
Observations when
starting materials
were mixed
Physical change or
chemical reaction?
Evidence
Did You Know?
NASA scientists originally thought that all gullies on Mars were caused
by water. After a series of experiments, scientists now think that
the new gullies are actually caused by dry ice flowing downhill and
subliming as it travels. In one experiment on Earth, they sent sledges
down sand dunes on large blocks of dry ice!
Science Starts With a Question: Chemical Reactions 11
Blue Bottle
? Question It
Note
This activity uses a
compound called
methylene blue, which is
an example of an indicator.
What are indicators used for
in chemistry? HINT: ask your
ambassador!
You will complete the rest of the lesson working in
pairs. The materials for all the activities are at each
workstation.
Materials
For each student
Safety goggles
Disposable gloves
For each pair of students
1 Measuring tube with a screw top filled with a liquid (labeled
‘Blue Bottle’)
Procedure
1.
Write down the appearance of the starting materials in
the table in question 1 of What Is Going On.
2.
Shake the tube for at least 10 seconds.
3.
After shaking, let the tube rest on the table or bench for
a minute or so.
4.
Write down your observations in the table in question 1
of What Is Going On.
5.
Your ambassador will let you know what to do with the
tube at the end of the activity.
Science Starts With a Question: Chemical Reactions 12
What Is Going On?
1.
What do the starting materials look like? What do you
observe when they mix? Use your observations to
decide whether a physical change or chemical reaction
has taken place.
Appearance of
starting materials
Observations when
starting materials
were mixed
Physical change or
chemical reaction?
Evidence
Magic Jell-O
Materials
For each student
Safety goggles
Disposable gloves
For each pair of students
1 Stoppered test tube containing a thick liquid
1 Ice bath
Science Starts With a Question: Chemical Reactions 13
Procedure
? Question It
1.
Write down the appearance of the starting materials in
the table in question 1 of What Is Going On.
2.
One student should hold the test tube labeled ”Magic
Jell-O” in one hand for 1–2 minutes to warm it.
3.
Write down your observations in the table in question 1
of What Is Going On.
4.
After observing what happens, cool the test tube in the
ice bath for 1–2 minutes.
5.
Your ambassador will let you know what to do with the
test tube at the end of the activity.
The liquid in the test
tube is a compound Dow
produces called Methocel.
It is an ingredient in veggie
burgers. Why do you think
this is? What are other uses
for Methocel? HINT: ask your
ambassador!
What Is Going On?
1.
What do the starting materials look like? What do you
observe when they mix? Use your observations to
decide whether a physical change or chemical reaction
has taken place.
Appearance of
starting materials
Observations when
starting materials
were mixed
Physical change or
chemical reaction?
Evidence
Science Starts With a Question: Chemical Reactions 14
Crushed Ice
Did You Know?
Materials
Athletes use ice packs to
reduce swelling and prevent
serious injury. They are most
effective when used in the
first 48 hours after an injury
occurs.
For each student
Safety goggles
Disposable gloves
1 Dynarex Instant Cold Pack
Procedure
Stay Safe
Let the teacher or ambassador know immediately if the instant cold
pack bursts.
1.
Write down the appearance of the starting materials in
the table in question 1 of What Is Going On.
2.
Squeeze the instant cold pack firmly but gently until
you feel something break inside the pack.
3.
Write down your observations in the table in question 1
of What Is Going On.
4.
Your ambassador will let you know what to do with the
used cold packs.
Science Starts With a Question: Chemical Reactions 15
What Is Going On?
1.
What do the starting materials look like? What do you
observe when they mix? Use your observations to
decide whether a physical change or chemical reaction
has taken place.
Appearance of
starting materials
Observations when
starting materials
were mixed
Physical change or
chemical reaction?
Evidence
Water Snakes
Materials
For each student
Safety goggles
Disposable gloves
For each pair of students
1 Beaker containing 125 mL calcium chloride solution
1 Beaker containing 25 mL sodium alginate solution
1 Plastic pipette
Science Starts With a Question: Chemical Reactions 16
Procedure
Stay Safe
Never touch any chemicals unless your teacher tells you it is safe to
do so.
1.
Write down the appearance of the starting materials in
the table in question 1 of What Is Going On.
2.
Using the pipette, suck up a small amount of the
sodium alginate and slowly add it to the calcium
chloride.
3.
Try adding the sodium alginate more quickly to the
calcium chloride.
4.
Put your hands into the calcium chloride beaker and
take out what has been made.
5.
Write down your observations in the table in question 1
of What Is Going On.
6.
Your ambassador will let you know the disposal
procedure at the end of the activity.
Science Starts With a Question: Chemical Reactions 17
What Is Going On?
1.
What do the starting materials look like? What do you
observe when they mix? Use your observations to
decide whether a physical change or chemical reaction
has taken place.
Appearance of
starting materials
Observations when
starting materials
were mixed
Physical change or
chemical reaction?
Evidence
Review
Let’s see how well you got to know the ambassador!
1.
What is the ambassador’s job title?
2.
What did you do today that is similar to what the
ambassador does?
Science Starts With a Question: Chemical Reactions 18
Lesson 3: Model Evaluation
Lesson Overview
In this lesson, you will review and refine your model from
Lesson 1. You will also test your prediction from Lesson 1 and
reflect on your understanding of chemical reactions.
Let’s Get Started
1.
Look back are the model you drew in Lesson 1
(question 3 of What Is Going On). Are you still happy
with this model? Redraw your model with any changes
below.
2.
Look back at your prediction from Lesson 1 (question 6
of What Is Going On). Are you still happy with your
prediction? Use your new model to make any revisions
to your prediction below. Explain what made you
change your mind.
Science Starts With a Question: Chemical Reactions 19
Reaction of Baking Soda and Calcium Chloride
in a Closed System
Your teacher will repeat the baking soda and calcium chloride
reaction. This time, your teacher will carry out the reaction in
a flask with a balloon on top. This is an example of a closed
system. Then your teacher will put the flask on an electronic
balance.
Key Term
Closed system: A sealed
container where nothing
can enter or leave.
What Is Going On?
1.
What is the mass before and after the liquids were
mixed?
Before:
After:
2.
Was your prediction correct? If not, explain what you
have learned about how the total mass changes during
a chemical reaction.
3.
What law explains the change in mass (if any) in this
activity?
Science Starts With a Question: Chemical Reactions 20
4.
Three wooden logs with a total mass of 15 kg were
burned in a fireplace. After burning for an hour they
were left to cool and then reweighed. The total mass of
the logs after burning was 8 kg. What happened to the
rest of the logs? Explain your answer using what you
have learned from this module. Use the terms reactant
and product in your explanation.
Key Term
Reactant: A substance that
takes part in a chemical
reaction.
Product: A substance that
is produced by a chemical
reaction.
Reflection
1.
Imagine you are a scientist working at Dow. How would
you explain to a non-scientist how to tell whether a
chemical reaction has taken place?
Science Starts With a Question: Chemical Reactions 21
Extending Your Knowledge
Edible Plastic?
You should never eat anything in the laboratory. However,
throughout this module you used several compounds you
probably eat all the time without even realizing it! Of course,
before anything is allowed in food or drink it undergoes
extensive testing to make sure it is safe to eat. In Magic
Snakes, you used a substance called sodium alginate. This
occurs naturally in giant kelp, or brown seaweed. Sodium
alginate is used widely to thicken food and help food last
longer.
One use of sodium alginate is in onion rings. Did you know
that onion rings are not actually whole onion rings? They
are chopped onions mixed with sodium alginate and made
into ring shapes. A preparer sprays the rings with calcium
chloride, and within seconds a skin forms, which holds the
ring together.
? Question It
What other foods contain
sodium alginate? Look
at the ingredient list of
food at home and in the
supermarket. What other
uses of sodium alginate can
you imagine?
Coating frozen food with a sodium alginate/calcium chloride
mixture also helps reduce the loss of moisture during
freezing. This preserves food longer in the freezer.
Sodium alginate has also been used to make fake caviar (fish
eggs) from fruit juice. The fruit juice is mixed with a small
amount of sodium alginate and then dropped into a bowl
filled with cold calcium chloride. In a few seconds, small fruitflavored balls form. If you ever go to a fancy restaurant, you
Science Starts With a Question: Chemical Reactions 22
might see these on the menu. You might also see them in a
Taiwanese drink called bubble tea.
Look It Up
A project is underway to
create an edible water bottle
made from sodium alginate.
However, scientists still need
to figure out how to close
the bottle! Visit http://www.
ssec.si.edu/Dow/Chemical to
read about this innovation.
One of the biggest problems with plastic is that it isn’t
recyclable. This means that it has to be thrown away in a
landfill site after use. Could sodium alginate help solve this
problem? A company called WikiFoods, Inc., has developed
a protective skin made of sodium alginate for foods such as
ice cream, yogurt, and even cheese. They call these coatings
Wikipearls. However, at the moment, Wikipearls are still sold
in a plastic wrapping.
Science Starts With a Question: Chemical Reactions 23