Pepper Pie

[20 Minutes]

Water is one of the few substances which exist commonly in three forms on earth- solid, liquid and gas. Water molecules are attracted to each other. The attraction of one water molecule to another is called cohesion. The result of the attraction or cohesion is called surface tension. If you carefully lower a needle onto the surface of the water, it will float because the weight is being supported by the "skin" or cohesiveness of the water molecules. If the needle is dropped onto the surface, it will break the surface tension and sink to the bottom. Try this experiment to see what happens.

You'll need:

• 2 pie plates • warm water • cold water • black pepper • liquid dish detergent in a small jar • toothpick

What to do:

1. If possible, print out these directions. Read them through together before you begin.
2. Together, gather everything you'll need and always remember science safety.
3. With your child, fill one of the pie plates with warm water, the other with cold water.
4. Let your child sprinkle some pepper onto the water in each of the pie plates and observe what happens.
5. Ask your child to touch the tip of the toothpick to the liquid soap in the small jar.
6. At the edge of the pie plate, let your child slowly immerse the soapy toothpick into the pie plate filled with warm water.
7. Ask her to repeat steps 5-6 using the pie plate filled with cold water.
8. If you repeat this experiment, it is important to rinse the pie plates so that no soap residue remains.
9. Be sure there is a definite temperature difference in the two water supplies.

Useful information:

Liquid detergent can be used to break the surface tension of water. Soap is used in the cleaning process because it surrounds dirt particles and speeds up the wetting process, making the washing process easier than without soap.