All matter is made up of atoms that form molecules. These molecules can either be polar or nonpolar. Polar molecules have a negative charge on one end and a positive charge on the other, but nonpolar molecules have no charge. Polar molecules tend to stick together. Nonpolar molecules stick together, too. You can illustrate these facts by doing the following experiments:
2 Tbsp. vegetable oil
Clear glass bowl
Glass jar with lid
Liquid dish detergent
Lesson One - Why Oil and Water Don't Mix
Fill bowl with water. Pour oil into paper cup and mix with a few drops of food coloring. Pour oil and food color mixture carefully into bowl and watch what happens after 10 minutes. The colored oil will settle on top of the water. As it settles, you will notice the coloring separate from the oil and forming streams of color as it sinks to the bottom of the bowl, finally mixing with the water. Your child should understand that oil and water do not mix because oil has nonpolar molecules and water has polar molecules.
Lesson Two - How Detergent Cleans
Have your child start again with just oil and water in a jar. Shake up vigorously, and then add a tablespoon of liquid detergent. The long detergent molecules are polar on one end and nonpolar on the other end. The nonpolar end grabs the oil while the polar end of the detergent molecule grabs the water, preventing the oil and water mixture from separating. Detergent is able to clean because it binds the dirt and oil with the water which all washes down the drain.
Your child will be learning scientific principles and concepts with these easy experiments, but you can encourage additional practice by washing the extra oily dishes on your kitchen counter too. Both science class and the dishes done in one easy step! What more could you ask for as a homeschooling parent?