Summary

In this activity, students explore the chemical reaction between borax and glue, creating a polymer ball. The properties of the polymer ball will be analyzed and compared to a store-bought bouncy ball.

Grade Level

Elementary school

Objectives

By the end of this lesson, students should be able to

• Describe what a chemical reaction is.
• Identify how a reaction can be used to make a new product.
• Understand the basic concept of a polymer.
• Compare properties of different substances.

Chemistry Topics

This lesson supports students’ understanding of

• Molecules
• Polymers
• Chemical reactions

Time

Teacher Preparation: 30-45 minutes

Lesson: 30 minutes

Materials

• Borax (you can buy this in the local grocery store, or online)
• Warm water
• Corn starch
• Glue (clear glue makes the ball transparent and white glue makes the ball opaque)
• Two small cups
• Measuring spoons (1 tbsp., ½ tsp.)
• Craft sticks or spoons for stirring
• Food coloring (optional)
• Pipe cleaners (optional)
• Store-bought bouncy balls

Safety

• Always wear safety goggles when handling chemicals.
• Remind the students not to consume any of the material.
• Remind students to be careful when bouncing the balls.
• Students should wash their hands thoroughly before leaving the lab.
• When students complete the experiment, instruct them how to clean up their materials and dispose of any chemicals.

Teacher Notes

• This works best when students work in small groups. If you can arrange for parent helpers for each group, the activity runs more smoothly.
• Depending on the age group, you could premeasure materials for groups so the measurements are accurate.
• Depending on the age of the students, you could complete steps 1-3 for them in advance.
• Before doing the experiment, to demonstrate what a polymer is, use pipe cleaners to show how monomers join to make a long, flexible chain.
• Vocabulary words are listed, but wait until the end of the lesson to discuss them so that students have a chance to hear and use the words during the activity.
• What chemistry is happening? The glue and borax react chemically, creating a polymer, which is a flexible chain of molecules. These molecules are what gives the substance its stretchiness and allows the ball to bounce.
• When the polymer balls have been created make sure each student gets a chance to roll the ball in their hands.
• The balls that are created from this activity are not exactly like the bouncy balls that you purchase from the store. The balls purchased from the store are rubber, which is made from a different compound than the polymer ball that the students create. Students can compare the ball they make to balls purchased from the store.

• Extension Suggestions based on the grade level of students:
  • Students compare and contrast the physical properties of the homemade polymer ball and the store-bought rubber bouncy ball. These properties could include stickiness, ability to retain its original shape, bounciness, stretchiness, etc.
  • Students design their own experiment to compare a physical property of their homemade polymer ball with the property of the store-bought bouncy ball. For example: create a test to determine which ball bounces higher. This would help students learn both experimental design and the scientific method.
  • Students design an experiment testing a property of only the homemade polymer ball. Some examples: change the height from which the polymer ball is dropped, to see how high it bounces each time. Cool the polymer ball to see if the temperature of the polymer ball affects the height of the bounce.
  • Note: during any extension experiments do not heat the homemade polymer, it will be dangerous when it is heated, acting like HOT glue, which could potentially burn skin.

• Vocabulary list:
  • Chemical reaction
  • Physical Change
  • Molecule
  • Polymer

• Procedures for making the polymer:

1. Label one cup Borax Solution and another cup Ball Mixture.
2. Pour 1/2 cup of warm water and 1 teaspoon of the borax powder into the Borax Solution cup. Stir the mixture to dissolve the borax.
3. Pour 1 tablespoon of glue into the Ball Mixture cup. If students would like to add food coloring, three drops should be added to this cup.
   This is where students get involved, if you chose to complete steps 1-3.
4. Add 1/2 teaspoon of the borax solution and 1 tablespoon of cornstarch to the glue in the Ball Mixture cup. DO NOT STIR!
5. After 10-15 seconds, stir the substances together.
6. It will eventually become impossible to stir. At that point, take the substance out of the cup and mold the ball with your hands. The ball will start out sticky and messy and will solidify as students knead it. When the ball is less sticky, students should roll it between their hands until it is smooth and round.
7. Students should compare how their ball bounces compared to a store bought ball.

Possible Discussion questions:

• How did liquids turn into a substance that bounces? Does your ball look like the one from the store? Do the two balls bounce the same? What does that mean about the two balls?
• Answers: The liquids underwent a chemical reaction, which formed a new substance, a polymer. The molecules in the polymer are closer together than they were in the liquid form, so we see that the polymer is more like a solid.
• The polymer ball and the store bought ball are made of different molecules, so they look and bounce differently.

Cross-Disciplinary Extensions

Connect to Math:

When connecting this activity to math, students will first make predictions of how high the ball will bounce and graph those predictions. Students can create the ball, and graph the bouncing data. Using DOK (Depth Of Knowledge) the students can COMPARE the results.

Connect to Reading:

• The Bouncing Ball, by Deborah Kelly & illustrated by Georgia Perry
• The Bouncy Ball (A Lesson Learned Book, Book 2), by Hilda Cuervo & illustrated by Alex Acayen

Connect to Writing:

Students can use the genre of opinion writing to express their thoughts and/or feelings of which ball is better: a homemade bouncy ball compared to a store bought bouncy ball.