You can make your own plastic "silly" putty by following a recipe from Wisconsin University. Mix, until completely dissolved, 1 tsp. of laundry Borax with 5 tbsp. water in a plastic cup. In a different cup, completely mix 1 tbsp. water with 1 tbsp. white glue. Pour 2 tsp. of the Borax mixture into the glue mixture. Stir until a soft lump forms. Knead the lump.
The experiment results in "gluep," a soft plastic. While the child plays with the material, illustrate different properties of plastics, including shape retention, shape formation and bounciness.
With an experiment from Exploratorium, soap and food coloring illustrate, through interesting and fun patterns, how different forces act on water.
Fill any clear-plastic bottle ¼ full with white liquid soap. Any size bottle will work for the experiment. Add two drops of red food coloring and fill the rest of the bottle with water. (Make sure that the water slowly pours into the bottle, to prevent suds.) After placing the cap on the bottle, turn the bottle gently a few times to mix the soap with the water. Swirl the bottle gently and look for color patterns in the mixture.
When playing with the bottle to create patterns, note the different movements the water makes with different movements of the bottle.
"Magically" inflating balloons with dry ice, using an experiment from Brian Wesley Rich's Science Website, can teach your children the effects of sublimation. (Sublimation is the chemical state change from a solid to a gas.)
Open the mouth of an uninflated balloon widely, so that a partner can drop a piece of dry ice in the balloon. Once the dry ice is inserted, tie off the balloon. Set the balloon in a sink full of water and stand back.
As the dry ice sublimates, the air pressure inside the balloon increases. The balloon begins to "magically" fill and float in the water; eventually it may pop. Encourage the child to answer the following questions: why does the balloon change size as the dry ice sublimates? Why does the balloon begin to float?
Always exercise caution when working with dry ice: never place dry ice in a closed bottle.
Dancing raisins experiments, like the one from Penn State University, illustrate the effects of gas on buoyancy. Fill a glass ¾ full with water. Mix in 1 tbsp .baking soda. After the water clarifies, add a small handful of raisins. Add vinegar in small amounts and watch the raisins' response.
As gas forms from the chemical reaction between baking soda and vinegar, it carries the raisins to the top of the glass. Not only does this experiment teach about chemical reactions and buoyancy, but it teaches children to think of solutions to problems (how do you move raisins without touching them?).