Disappearing Cup

Science Concepts: Polarity, Solubility To see the difference between how polar and non-polar things dissolve.

Materials:

* A pie plate

*50 mL of water

* 50 mL of acetone (this can be replaced with finger nail polish remover)

* 3 Styrofoam cups

Directions: Procedure A - Bottom Falls Out

1. Give one cup to a person, and you hold the other one.

2. Give the person a cup full of acetone in a glass beaker or jar and you take the one full of water.

3. Both people pour the "water" into their styrofoam cups. Make sure that the cup with acetone is held over the pie plate to catch the remains.

4. Observe what happens.

5. Finish by putting the cup into the pie plate and watch it disappear.

Alternate Procedure B - Tower of cups

1. Start with two pie plates and put about a 1/2 inch of acetone in the bottom of one and the same amount of water in the second.

2. Have a race to see how can make the tallest tower of cups.

3. The cups in the acetone will slowly dissolve and shrink into the acetone, while the ones in the water will remain intact.

 

Introduction:

I decided to think of a prank for April fools day, and I found this to be the best idea.

Alternate Introduction: In the laboratory, one of the safety rules is to never drink in the lab. This will show you why this is a good idea. Here we have two colorless liquids that appear to be water. I think I will take a drink of this water. Pour the real water into the cup and take a drink. Next, I am still thirsty so I will try the next glass of water. This time, pour the acetone into the cup. The results show why you should not assume that something in the lab that looks like water, is water.

Explanation:

A Styrofoam cup is made of styrofoam. The styrofoam cup is a polymer, and a polymer is a long chain of monomers. 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.

When the acetone was poured into the cup, the cup dissolved. (Avoid saying that the cup melts, because this is not true). The reason for this happening is because the acetone and the Styrofoam cup share the same properties, they are both non- polar. Likes dissolves likes. Non-polar things have no charge, and polar things have positive and negative charges. The Styrofoam cup didn't dissolve with the water because, they have different properties, the water is polar, and the cup is non-polar. Acetone is actually what girls use to take off their nail polish.

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