Kelly Brechin

The Great Peanut Race

SCIENCE CONCEPT: Polarity, Solubility - Certain chemicals weaken the bonds in a polymer. "Likes dissolve Likes".

MATERIALS:

two - 600 mL beakers

30 mL of water

30 mL of acetone

Styrofoam packing peanuts

Starch based packing peanuts

DIRECTIONS:

1. Place a few starch based packing peanuts in a beaker of water. Dunk the peanuts under the water a couple of times.Have the students notice that the packing peanuts are now slowly dissolving.

2. Fill one 600 mL beaker with 30 mL of water and fill the other 600 mL beaker with 30 mL of acetone.

3.   Choose two students from the audience to come up and help you .

4. Have the students try to fill up their beaker with the Styrofoam packing peanuts. One student should have the beaker that contains the acetone and the other student should have the beaker containing the water.

5. Have the class observe what happened to the packing peanuts that were added to each beaker. The packing peanuts should still be present in the beaker containing water. The packing peanuts should have dissolved in the beaker containing the acetone.

INTRODUCTION: Do you guys like to play games? Well, today I have a game for two of you to play. Can I have two volunteers from the audience to help me out? The object of the game is quite simple. All you need to do is fill your beaker with the most amount of packing peanuts. The person with the most amount of peanuts in their beaker after 30 seconds wins.

EXPLANATION: The packing peanuts that you were using were actually made of Styrofoam. The styrofoam packing peanut is a polymer, and a polymer is a long chain of monomers molecules called styrene. The long chain polymers are held together rather loosely by non-polar bond interactions between the chains. In addition, the polymer is made as a foam so there are lots of air spaces between groups of polymers. Styrofoam is a non-polar substance, which means it has no charge to it.

In one of the beakers, I put 30 mL of water, and in the other beaker, I put 30 mL of acetone. Acetone is also a non-polar substance. Acetone is actually what girls use to take off their nail polish. Since both the Styrofoam and the acetone were non-polar, the Styrofoam peanuts dissolved because LIKE DISSOLVES LIKE. Water, on the other hand, is polar which means it has a charge. Since water is polar and the peanuts were non-polar, the peanuts are not able dissolve.

In the last beaker, I placed a few starch based packing peanuts into some water. The packing peanuts began to dissolve, but much slower than the Styrofoam packing peanuts did in the acetone. The starch based packing peanuts are made up of long polymer chains of glucose. The starch peanuts are polar and so is water, which is why the peanuts began to dissolve. Like dissolves like. So the starch based packing peanuts are considered to be biodegradable, which means they will degrade or dissolve if left outside as litter. The styrofoam will not dissolve.

Safety: No particular cautions are needed.

Disposal: It is probably easiest to pour off the extra liquid acetone down the drain. The gooey solid is mostly easily disposed by wiping it up with a dry paper towel. This can be put in the trash.

Reference: Public Domain