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ChemicalReactions

Student Guide

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Science Starts With a Question

Science Starts With a Question: Chemical Reactions i

Science Starts With a Question is a collaboration between the Smithsonian Science Education Center and The Dow Chemical Company.

About the Smithsonian InstitutionThe 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 CenterThe 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 Editors

Ashley Deese Designer

Elizabeth Klemick Brannan Proofreader

Taryn White Production Specialist

Marjee Chmiel, PhD Associate Director for Curriculum and Communications

Amy D’Amico, PhD Director of Professional Services

Eric Nastasi, Esq. Senior Advancement Officer

Lisa Rogers Director of Finance

Teng Chamchumrus Interim Director Teachers involved in development of this publication

David Brown Science TeacherBullock Creek Middle School, Michigan

Scott Harrison Science TeacherFreeland Elementary School, Michigan

Science Starts With a Question: Chemical Reactions ii

About The Dow Chemical CompanyDow’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 publicationPatrick 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 iii

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

Did You Know?

Question It?

Stay Safe

Look It Up

These explain new science words and terms.

Science is fun but can also be dangerous. The advice in these boxes will help you stay safe.

Interesting and fun facts relate to the activities you are carrying out.

Research these questions to dig a little deeper.

Visit these websites for further reading.

Science Starts With a Question: Chemical Reactions 1

Science Starts with a Question

Chemical ReactionsCentral QuestionHow can I tell if I have made something new?

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 DevelopmentLesson 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.

Chemical reaction: What happens when substances mix to form new substances.

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.

Did You Know?

Key Term


Question It?One use of calcium chloride is to keep canned vegetables firm. What other food and drink is calcium chloride added to?

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.


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:

Dress appropriately for the laboratory. Wear long sleeves and shoes that completely cover your feet. Wear your safety goggles at all times when working with chemicals.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.Be careful when touching anything that may be hot or cold.If you spill a chemical or break any glass, tell your teacher or ambassador immediately.If you get a chemical on your hand, wash your hands immediately with soap and water.Never taste chemicals.When smelling in the laboratory, ”waft” the smell toward you using your hand.


Procedure

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.

Stay SafeThermometers are glass and break easily.

Did You Know?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.


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.


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.


Review

1. 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.

Key Term


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!

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.

NoteSTEM stands for Science, Technology, Engineering, and Math.


Fog Maker

The ambassador will drop some dry ice—solid carbon dioxide—into a graduated cylinder of warm water.

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

Stay SafeDry 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.

Sublimation: When a solid heats and changes straight to a gas.

Key Term


Chemiluminescence: A chemical reaction that gives off light.Bioluminescence: A chemical reaction that gives off light inside a living organism.

Crime Scene Investigation

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?




were mixed


Evidence

Did You Know?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.

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.

Look It Up

Key Terms


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?




were mixed


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!


Blue Bottle

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.

NoteYou will complete the rest of the lesson working in pairs. The materials for all the activities are at each workstation.

Question It?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!


What Is Going On?




were mixed


Evidence

Magic Jell-O

Materials

For each student

Safety goggles

Disposable gloves


1 Stoppered test tube containing a thick liquid

1 Ice bath


Procedure


2. One student should hold the test tube labeled ”Magic Jell-O” in one hand for 1–2 minutes to warm it.


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.

What Is Going On?




were mixed


Evidence

Question It?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!


Crushed Ice

Materials

For each student

Safety goggles

Disposable gloves

1 Dynarex Instant Cold Pack

Procedure


2. Squeeze the instant cold pack firmly but gently until you feel something break inside the pack.


4. Your ambassador will let you know what to do with the used cold packs.

Stay SafeLet the teacher or ambassador know immediately if the instant cold pack bursts.

Did You Know?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.


What Is Going On?




were mixed


Evidence

Water Snakes

Materials

For each student

Safety goggles

Disposable gloves


1 Beaker containing 125 mL calcium chloride solution

1 Beaker containing 25 mL sodium alginate solution

1 Plastic pipette


Procedure


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.


6. Your ambassador will let you know the disposal procedure at the end of the activity.

Stay SafeNever touch any chemicals unless your teacher tells you it is safe to do so.


What Is Going On?




were mixed


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?


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.


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.

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?

Closed system: A sealed container where nothing can enter or leave.

Key Term


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.

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?

Reactant: A substance that takes part in a chemical reaction.

Product: A substance that is produced by a chemical reaction.

Key Term


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.

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 fruit-flavored balls form. If you ever go to a fancy restaurant, you

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?


might see these on the menu. You might also see them in a Taiwanese drink called bubble tea.

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.

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.

Look It Up

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