How to Engineer Your Own Bouncy Ball

How to Engineer your own Bouncy Ball

Name: Date:

Purpose: How to engineer a bouncy ball using readily available household items. In this lab we will see how Borax can be used to cross-link the polymers in glue to form a rubbery like material capable of bouncing. Also we will see how vinegar can be used to neutralize the solvent used in liquid latex rubber molding material leaving behind only latex rubber (an excellent bouncy material!).

Question: When you add borax to Elmer’s glue it will solidify into a rubbery like substance. Why do you think this occurs?

Hypothesis:

State your hypothesis for the above question and explain your reasoning:

Materials Needed:

1  Elmer’s white glue-all

2  Borax powder

3  Epsom Salt

4  Digital scale

5  Liquid latex

6  Vinegar

7  Graduated cylinder

8  4 small disposable plastic cups

9  4 plastic stirring rods or wooden stick

10  Food coloring

11  Sealable plastic bags

12  Paper towels

13  Meter stick

Procedure:

Making Ball # 1 – Soft Ball

1  Use a graduated cylinder to measure 20 ml of water and pour into a cup

2  Use the scale to weigh 0.5 g of Borax powder and add to the water in the cup. Stir to dissolve the Borax into the water

3  Measure 10 mL (1 tbsp) of glue into another plastic cup

4  Slowly add the Borax water solution to the glue while stirring

5  Continue stirring the mixture until it clumps and sticks to the stirring stick

6  Remove the clump from the stick. Hold it under running water and mold into a ball

7  Pat the ball dry and try to bounce it on the table top

8  Squeeze the ball then stretch it

9  Hold under water again and mold into a ball. Try to make it as round as possible.

10  Label a zip lock bag as ball #1 and store your ball for the activities

Making Ball # 2 – Hard Ball

1  Measure 10 mL of glue into a plastic cup

2  Use the scale to weigh 5 grams of Epsom salt and add to the glue

3  Stir vigorously until the mixture clumps and sticks to the wooden stick.

4  Remove the clump of polymer from the stick. Hold it under running water and shape into a ball

5  Pat the ball dry and bounce it on the table top.

6  Label a zip lock bag as ball # 2 and store your ball for the activities.

Making Ball # 3 – Medium Ball

1  Measure 10 mL of glue into a plastic cup

2  Use the scale to weight out 5 grams of Borax powder and slowly add to the glue while stirring

3  Stir vigorously until the mixture clups and sticks to the wooden stick

4  Remove the clump of polymer from the stick. Hold it under running water and shape into a ball.

5  Pat the ball dry and bounce it on the table top.

6  Label a zip lock bag as ball #3 and store your ball for the activities.

Making Bal # 4 – A truly rubber ball

1  Measure approximately 15 mL of liquid latex rubber into a plastic cup

2  Use a graduated cylinder to measure 15 mL of water and add to the liquid latex in the plastic cup

3  Stir the water and latex mixture until thoroughly mixed

4  Use a graduated cylinder to measure 15 mL of vinegar and use a dropper to slowly add the vinegar to the liquid latex/water mixture while your partner stirs continuously

5  When the mixture thickens remove it from the cup and hold under water and shape into a ball

6  Pat the ball dry and bounce it on the table top

7  Label a zip lock bag as ball # 4 and store your ball for the activities

Data & Activities:

Ball # 1 Description: State what it looks like, how it feels and how it bounces

Ball # 2 Description: State what it looks like, how it feels and how it bounces

Ball # 3 Description: State what it looks like, how it feels and how it bounces

Ball # 4 Description: State what it looks like, how it feels and how it bounces

Check the rebound heights of each ball you just made by dropping from 50 cm and recording the data in the table below.

Table 1: Rebound Heights for the 4 balls from 50 cm

Ball Dropped (#) / 1 / 2 / 3 / 4
Rebound Height in Centimeters / Trial 1
Trial 2
Trial 3
Sum
Average

Graph your results for each Ball in the following graphs. Generate a bar graph indicating rebound height fr each ball you created in the procedures above.

Conclusion:

1  What did you do in this lab? (Re-state the purpose/problem being investigated, how you tested your hypothesis and what you used to gather data)

2  What happened when you added the Borax to the glue?

3  What happened when you added the Epsom salt to the glue?

4  What happened when you added the vinegar to the liquid latex/water mixture?

5  Which ball bounced the highest and what are the main factors that determine why it bounces higher than the others?

6  Is the material the ball is made from important? Why?