Drying is an ancient method of keeping food from spoiling. Cut apples into slices one-quarter inch thick. Put them into a bath of two cups of lemon juice. Place slices onto paper towels to absorb excess liquid. Line the apple slices on a cookie sheet and put these into the oven at 150 degrees for about 5-12 hours. The apples are drying, not cooking. After two hours, turn the apples around. Test for doneness when the apple slice is pliable, but without liquid. Discuss how the apple changed. Cool, then store them in plastic bags for snacking.
The food inside corn kernels is to feed baby corn plants, but people like to eat it popped. Popcorn kernels may look dry; however, they contain water. When heated, the pressure inside the kernel increases and the water of the kernel turns to steam, and this force causes the seed coat to explode. Experiment by adding dry kernels to a pot with about a tablespoon of cooking oil. Cover the pot and place on the stove on low and listen for the kernels popping. When the popping stops for about two seconds, take the pot off the heat. Discuss how the hard kernels changed to a fluffy puffed snack.
Add a small amount of raisins to a glass of freshly opened soda (clear soda like lemon-lime is best). The carbon dioxide bubbles will cling to the raisins, allowing them to wiggle and dance as they rise to the top of the liquid. When the bubbles burst, the raisins will sink to the bottom again and collect new bubbles, causing them to rise once more. It's an experiment that will make children giggle.
Place two cups of heavy cream into a plastic container with a lid. Add a glass marble, which you have previously washed and dried, and cover with the lid. Turn on some music and let the child shake, shake, shake the container. In about 15 minutes, the butter should separate from the thin white liquid (buttermilk). Take out the marble and excess liquid and chill the butter. Discuss how movement caused the liquid to turn into a solid. Taste it on a cracker -- it will be sweet. Add salt if desired.