How Small are Atoms?
This experiment can be performed with only a pair of scissors and a strip of paper. Cut a sheet of colored paper into 11-inch long strips, providing one strip for each student doing the project. Give each student a pair of scissors. Instruct students to cut the paper strip in half, then cut those halves into halves. Have them keep cutting the strip pieces into halves as many times as possible. (Make sure they always cut in the same direction; when the strips become much wider than they are long, they can trim off the excess, but those cuts don't count as cutting it in half.) By the eighth cut, the paper pieces would be about 1 millimeter wide each; by the tenth, the pieces would be about 0.23 millimeters wide. Students won't be able to cut the paper smaller than this. Tell them that to make the pieces as small as an atom, they would need to cut each one in half 31 times.
By building models of molecules with soft candy, kids can get a visual idea of what these invisible components look like. Gather a box of toothpicks, a bag of gumdrops and a bowl. Separate the gumdrops based on color, then assign an atom to each color of gumdrop. Yellow candies may signify hydrogen, for instance, while red candies depict oxygen. Make a few simple molecules, such as carbon dioxide, or CO2. This molecule uses one carbon atom and two oxygen atoms. Stick the correct color of gumdrops on the ends of toothpicks to assemble the molecule. This can be done with any molecule you want, and afterward, the molecules can be eaten.