Teach your preschoolers about air. Use this experiment to allow them to see that air is matter that takes up space. Give each preschooler a small bowl of water with 10 drops of dish soap in it. Let them use a straw to create bubbles. Then provide the children with pans of bubble solution and several different types of bubble wands. Let the children blow the bubbles to see what shape each wand makes. Teach them how to catch the bubbles with the wands and form bubble clusters.
Teach preschoolers about evaporation with this simple science experiment on a sunny day. Give each child a small bucket of water and a 2- to 4-inch paintbrush. Assign a section of sidewalk to each child. Let each child paint a picture on the sidewalk with the paintbrush and water. Then sit in the grass and watch the pictures disappear as the water evaporates. Talk with the preschoolers about where the water went and why it went there.
Dancing Raisins is an easy experiment for little ones that will demonstrate either buoyancy or density as gas bubbles attach to the raisin at the bottom and burst when they reach the surface. Prepare the following items for each child: one 16-ounce, clear, plastic cup half-full of water; a plastic bag containing 1 teaspoon of baking soda; a stir stick; a small plastic glass full of vinegar; and six or seven raisins. Place a black line on the large glass to show where the cup would be three-fourths full. Tell the children to pour the baking soda in the 16-ounce cup and stir it with the stir stick until the soda dissolves. Add the raisins. Have the children slowly add the vinegar and watch the fun as the raisins start to dance.
Create a simple volcano with a yogurt cup and clay. Give each child one empty yogurt cup, sitting upright on a Styrofoam plate. Use play clay and press it against the sides of the yogurt cup to create a volcano. Put a tablespoon of baking soda in each cup. Give each child a small cup half-full of vinegar that is colored with red food coloring. Tell the children to pour the vinegar into the yogurt cup. The chemical reaction will cause the mixture to pour over the side of the cup.