Polarity and Solubility: Breaking Bonds of Packing Peanuts (page 2)

Packing peanuts, which are used to cushion breakable items during shipment, may be made of either synthetic or natural materials. Cornstarch peanuts are natural polymers made of chains of glucose. They are held together by polar bonds, which form between particles with slight charges. Styrofoam peanuts are made from a synthetic material composed of long chains of styrene. Bonds in styrene are nonpolar because the particles are not charged.

Certain liquid solvents (chemicals that dissolve solutes) will break the bonds holding the peanuts together and cause them to dissolve. Following the ''like-dissolves-like'' rule, polar solvents dissolve polar substances, and nonpolar solvents dissolve nonpolar substances. In this activity you will determine the polarity of solvents used to dissolve Styrofoam and cornstarch packing peanuts.

Materials

Safety goggles

Four baby food jars (or other small glass jars) with lids

Nail polish remover (acetone)

Black wax pencil

Water

Several Styrofoam packing peanuts

Several cornstarch packing peanuts

Activity

1. Put on your safety goggles.
2. Use a wax pencil to label two jars as ''Cornstarch.'' Place two cornstarch peanuts in each of those jars.
3. Label the other two jars as ''Styrofoam'' and place two Styrofoam peanuts in each jar.
4. Pour two inches of water each into one of the ''cornstarch'' jars and one of the ''Styrofoam'' jars.
5. Pour two inches of nail polish remover into the remaining two jars. Replace the four lids.
6. Observe what happens in the four jars. You may need to swirl the liquid around in the jars to mix it with the peanuts.

Follow-Up Questions

1. Describe what happened in the four jars.
2. Using the ''like-dissolves-like'' rule, indicate the polarity of water and the polarity of acetone.

Answers

1. The water dissolved the cornstarch peanuts, but not the Styrofoam peanuts. The nail polish dissolved the Styrofoam, but not the cornstarch peanuts.
2. Water is polar, as is the cornstarch. Styrofoam is nonpolar, as is acetone.

Extension

WD-40 is a liquid lubricant made of nonpolar bonds. Do you think balloons are made of polar or nonpolar bonds? Blow up a balloon and spray some WD-40 on it and then answer that question.