The foamy peanuts that fall out of packing boxes are made of a synthetic plastic substance called styrene. These peanuts protect the items inside the box but are remarkably fragile to simple solutions of acetone. Pour some acetone into a glass bowl then drop a styrene peanut into the acetone. The acetone dissolves the peanut and makes the peanut appear to disappear. In fact, the peanut was made up mostly of air, and all that is left is the plastic material. Acetone is flammable so children should be supervised and must wear gloves during the experiment. Disposable foam cups also dissolve when the experimenter places them into a bowl and pours acetone into the cup.
Sugar and salt dissolve in water, but by varying the conditions and changing the experimental parameters, the rate at which they dissolve changes. The materials necessary are glass beakers, cold and hot water, powdered sugar, sugar cubes, sea salt and table salt. Place a sample of each of the sugar and salt types into eight different beakers. There will be two beakers for each sample. Add hot water to one beaker of each set and cold water to the other. Measure the amount of time it takes for the sugar or salt to dissolve. Another twist to this experiment is to set up a third duplicate set of materials and stir them continuously to see if they dissolve quicker than those that are not stirred.
Kids find out just how strong household bleach is by using it to dissolve hair. Obtain a clump of hair from the hair salon, or even snip it off a long-haired dog with permission from its owners. Bleach is a strong solvent and so adult supervision is necessary. Fill up a glass beaker 1/4 of the way up with bleach and place the hair into the solution. After 20 minutes the bleach will have dissolved the hair and left foam behind. As an alternative to hair, use a square of cotton.
One of the tastiest of dissolving experiments also uses one of the least hazardous of materials. Lay out three identical chocolate candies on a desk. Pop one into your mouth, but do not chew it or move it around in your mouth. Use a stopwatch to measure the time it takes to melt. Then place another of the candies in your mouth and move it around until it melts, measuring the time it takes. Finally, chew up the third piece of candy without swallowing to see if that makes it dissolve any quicker. Results will show whether or not small pieces of candy dissolve quicker than one large piece, and if moving the candy inside the mouth helps it dissolve.