Have you ever helped with cooking and gotten oil on your hands? It’s hard to get off! Rinsing with water does not work; you need to use soap. The reason is the molecules that oil and water are made of. Everything in our world is made of molecules, tiny parts we can’t see. But not all molecules are the same! Because of the way the parts of the molecules stick together, some molecules, called polar molecules, are like magnets, while others are not. Polar molecules interact with each other, like how a magnet will stick to your refrigerator. But just like a magnet won’t stick to a piece of wood, polar molecules won’t interact with nonpolar molecules. This is the secret to oil and water! Water is a polar molecule, while oil is not. They don’t interact, so water won’t rinse the oil off your hands. You can explore what kind of molecules different liquids are made of by seeing how they interact with other things. In this sweet experiment, we are exploring how 3 colorless liquids interact with candy-coated chocolates.
Materials: Candy-coated chocolates (like M&Ms), 3 clear cups, water, oil (colorless like baby oil is best) and isopropyl alcohol, 70%.
Directions: Pour equal amounts of water, oil, and alcohol in each of the 3 cups. Make a prediction about what will happen to the M&M in each liquid, then place a candy in each cup. For the best results, use the same color candy in all 3 cups. Swirl the cups and make observations. What color is the water? What happened to the candy coating?
How It Works: The candy coating on chocolates like M&Ms is made of sugar and food coloring. The sugar is made of a polar molecule, just like water, so the sugar and water interact. This causes the sugar and food color to dissolve, or melt, into the water. The alcohol is less polar than water, so it dissolves some of the candy coating, but more slowly and not as well. The oil is made of a different kind of molecule that does not interact with the sugar in the candy coating, so nothing happens.
Want more? Research it! How do molecule types impact what can get in and out of cells?