Chemistry is Cool Project Skills: Following directions Life Skills: Learning to Learn, Critical thinking Academic Standards: SC.A.1.3 #5; SC.B.1.3 #2 Grade Level(s): 6‐8 Time: 60‐90 minutes Supplies Needed: Ice Cream in a Bag • 1 quart freezer bag • 1 gallon freezer bag • Measuring spoons and cups • Thermometer • ½‐3/4 cup rock salt Not Supplied • ½ cup milk • ½ cup half and half • ¼ cup sugar • ¼ tsp vanilla • 2 cups ice BACKGROUND Chemistry can be a very intimidating subject that is hard for some students to understand. This fun experiment helps demonstrate some basic principles of chemistry. Specifically, these activities help students understand that there is a difference between a physical change and a chemical change. The activities also help students understand that energy can never be created or destroyed, but is simply transferred from one form to another. INTRODUCTION Chemistry is the scientific study of matter, and how it works together with other matter and energy. Chemists are scientists that study what happens when they mix different substances together and how different substances change when they are heated or cooled. There are basically two types of chemical changes: • Physical changes‐ this occurs when you mix, heat, or cool substances to change their shape, form, volume, or density. • Chemical changes‐ when you mix, heat, or cool substances to create new substances with different characteristics. Today, we will be chemists and will conduct three different experiments in our laboratory. To make sure you do the experiments correctly, you will need to listen carefully and follow directions exactly! WHAT TO DO Ice Cream in A Bag­ Ice cream is really a chemical reaction that requires temperature change. Temperature change is nothing more than an exchange of energy. In this case, the salt actually lowers the temperature of the ice, causing the milk and cream to freeze. Here’s how: Add 1/4 cup sugar, 1/2 cup milk, 1/2 cup whipping cream, and 1/4 teaspoon vanilla to the quart bag. Seal the bag securely. Put 2 cups of ice into the gallon bag. Use a Equal Opportunity/Affirmative Action Institution
Supplies Needed: Borax Snowflakes • String • Wide mouth jar • White pipe cleaners • Borax • Pencil • Food coloring (optional) • Scissors • Boiling water (not supplied) Polymer Ball • Borax • Cornstarch • White glue (Elmer’s) • Measuring spoons • Craft stick • 2 plastic cups • Sharpie • Watch or timer • Metric ruler • Zip‐lock bags • Warm water (not supplied) Advance Preparation: • Read over the lesson plan and make sure you have all the supplies needed. thermometer to measure and record the temperature of the ice in the gallon bag. Add 1/2 to 3/4 cup rock salt to the bag of ice. Place the sealed quart bag inside the gallon bag of ice and salt. Seal the gallon bag securely. Gently rock the gallon bag from side to side. It's best to hold it by the top seal or to have gloves or a cloth between the bag and your hands because the bag will be cold. Continue to rock the bag for 10‐15 minutes or until the contents of the quart bag have solidified into ice cream. Open the gallon bag and use the thermometer to measure and record the temperature of the ice/salt mixture. Remove the quart bag, open it, and serve the contents into cups with spoons. Each bag makes about 4 servings. TIP‐ When you use ice to cool the ingredients for ice cream, the energy is absorbed from the ingredients and from the outside environment (like your hands, if you are holding the baggie of ice). When you add salt to the ice, it lowers the freezing point of the ice, so even more energy has to be absorbed from the environment in order for the ice to melt. Question‐ Did you create a physical or chemical change? Borax Snowflakes­Snowflakes are beautiful crystals, but very tiny. You can make a large snowflake that you can enjoy year round by making your own borax crystals. In this experiment, you will be using water and borax to make a completely different substance (crystals). Here’s how: Cut a pipe cleaner into three equal sections. Twist the sections together at their centers to form a six‐sided snowflake shape. Don't worry if an end isn't even, just trim to get the desired shape. The snowflake should fit inside the jar. Tie the string to the end of one of the snowflake arms. Tie the other end of the string to the pencil. Equal Opportunity/Affirmative Action Institution
You want the length to be such that the pencil hangs the snowflake into the jar. Fill the wide‐mouth jar with boiling water. Add borax one tablespoon at a time to the boiling water, stirring to dissolve after each addition. The amount used I s 3 tablespoons borax per cup of water. It’s okay if some un‐
dissolved borax settles to the bottom of the jar. If desired, you may tint the mixture with food color. Hang the pipe cleaner snowflake into the jar so that the pencil rests on top of the jar and the snowflake is completely covered with liquid and hangs freely (not touching the bottom of the jar). Allow the jar to sit in an undisturbed location overnight. Question‐ Did you create a physical or chemical change? Bouncing Polymer Ball­Balls have been toys practically forever, but the bouncing ball is a more recent innovation. Bouncing balls were originally made of natural rubber, but now they come in a variety of plastics and polymers. You can use chemistry to make your own bouncing ball. The bouncing ball in this activity is made from a polymer. Polymers are molecules made up of repeating chemical units. Glue contains the polymer polyvinyl acetate (PVA), which cross‐links to itself when it reacts with borax. Label one cup 'Borax Solution' and the other cup 'Ball Mixture'. Pour 2 tablespoons warm water and 1/2 teaspoon borax powder into the cup labeled 'Borax Solution'. Stir the mixture to dissolve the borax. Pour 1 tablespoon of glue into the cup labeled 'Ball Mixture'. Add 1/2 teaspoon of the borax solution you just made and 1 tablespoon of cornstarch. Do not stir. Allow the ingredients to interact on their own for 10‐15 seconds and then stir them together to fully mix. Once the mixture becomes impossible to stir, take it out of the cup and start molding the ball with your hands. The ball will start out sticky and messy, but will solidify as you knead it. Once the ball is less sticky, you can bounce it! You can store your plastic ball in a sealed ziploc bag when you are finished playing with it. Don't eat the materials used to make the ball or the ball itself. Wash your work area, utensils, and hands when you have completed this activity. Question‐ Did you create a physical or chemical change? TALK IT OVER Sharing‐ • Which experiment was your favorite? Why? • What surprised you most about these experiments? Equal Opportunity/Affirmative Action Institution
Processing‐ • What problems did you have with the experiments? • Why do you think it is important for you to know about chemistry? • What did you learn from these experiments that you didn’t know before? Generalizing‐ • How will learning about chemistry benefit you in the future? Applying‐ • How would you teach someone else about what you learned today? • Describe a time or situation when you might need to use what you learned today. • What would you do differently if you did these experiments again? ENHANCEMENT When you use the scientific method, you make observations before forming or testing a hypothesis. You've followed a procedure to make a bouncing ball. Now you can vary the procedure and use your observations to make predictions about the effects of the changes. Observations you can make and then compare as you change the composition of the ball include the diameter of the finished ball, how sticky it is, how long it takes to solidify into a ball, and how high it bounces. Experiment with the ratio between the amounts of glue, cornstarch, and borax. Adding more cornstarch will make a ball that stretches and bends. Using less borax will produce a 'gooier' ball. Adding more glue makes the ball more slimy. This activity is adapted from the American Chemical Society's Meg A. Mole's Bouncing Ball, a featured project for National Chemistry Week 2005. TRAINER TIP An icebreaker is a fun way to introduce a topic and excite the youth. Here are a couple of ideas: • Periodic Predicament‐ Make up 2 sets of cards‐ one set that has the symbols of elements printed on them, and the other set should have the matching elements spelled out as words. Mix the cards up, and give one to each youth. See how many youth can find their match. Equal Opportunity/Affirmative Action Institution