Resource Title:

Bounce

Description:

The properties of a material make it just right for some purposes. In this activity, you will explore the special properties of latex rubber and discover how this valuable material can be used and reused.

Target Grade Level:

Grades K-4

Discipline or Course (Audience):

Science

Time Frame:

One to two 45-90 minute sessions without extensions

Suggested Grouping:

3-4 students

Educator Prep:

National, state, and local standards ask students to develop an understanding of the properties of matter. The unique properties of organic polymers make them essential for many products. One valuable polymer is rubber. In chemical terms it is an elastomer (an elastic hydrocarbon polymer) and a thermoplastic (changing its flexibility depending on the temperature.) Natural latex rubber is extracted from rubber trees grown in tropical zones. The tree lives for about 32 years, using a great deal of water and nutrients. To make natural rubber more durable and less sensitive to temperature changes, it is vulcanized—a process invented by Charles Goodyear in 1839, which changes the sulfur bonds between its long molecules and improves its resistance and elasticity in lower temperatures. Carbon black is often added to improve its strength in tires.

Rubber is also an ideal material for sports balls like racquetballs. The standard ball has a diameter of 2.25 inches. Rubber is almost always the material of choice. In the activity, students discover that the elasticity of a racquetball changes with temperature. They examine the requirements of a good running track (resilience and elasticity) and compare them to those of a good automobile tire to develop an understanding that chemical engineers design materials with the ideal properties for certain purposes.

Figure 1: Recycled Tire Merry-Go-Round

Make Observations: Teacher Directions

Divide teams into groups of 3-4 students. Pass out a piece of a racquetball. Have students make observations and list at least 5 traits (have them consider texture, smell, weight or mass, color, size, and what happens when pulled or twisted?
Discuss the word elasticity (the ability of an object or material to resume its normal shape after being stretched or compressed; stretchiness). Have students conduct activity.
Depending on grade level and abilities, you may include a more extensive exploration of density, and have students actually calculate it (using displacement method in water to calculate volume, and a scale for mass, where d=m/v). At the most basic level, floating vs. sinking in water is a good way to get a general idea of density (objects more dense than water will sink; objects less dense than water will float). This portion of the activity is a quick and good way of getting kids into “observation mode” and measuring qualities of a material that a scientist might also do if he/she were learning more about its behavior and properties. 

Warm Up: Teacher Directions

The warm-up portion of the activity should have students thinking about procedure and methods. This is a good time to challenge them to think about how many times (trials) they should do their test and why. How can they repeat it the same way each time? This is also a good time to discuss with students the importance of dropping balls from a certain height, same height each time. Throwing the balls down will: lead to safety issues (hitting someone or something); be hard to measure (because it will go too high or off at a different angle); and make it difficult to control the force with which they throw the ball down every time which could lead to errors. This gives students a chance to think about experimental design and science practices. Discuss and review as a whole class. Eventually, students will follow the guidelines provided in the lab as one example of how to control the variables and plan a safe experiment. Depending on age and ability, you might also allow students to follow their own procedures as long as they are safe and workable.

Test the Bounce: Teacher Directions

Provide guidance as needed during the experiment. Review how to calculate an average as necessary. For younger audiences, you may need to skip this.

Preparation Directions:

• Gather materials.
• Replicate Supporting Material - Student Data Sheet: Bounce (one per student).
• Prepare to project the photo of the recycled-tire Merry-Go-Round.
• Cut one racquetball open to show students the hollow core. Use part of this ball to cut smaller pieces for teams to make observations with and test density. A whole ball can also be used for observations, but pieces are necessary for testing density.
• Verify that latex is permitted in your classroom (check for latex allergies and with administration).

Remote Learning Adaptations:

This activity can be conducted online as a demonstration.

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