Florists create interesting and unusual flowers by changing their colors or creating multiple colors by using food coloring and water. Prekindergarten teachers can replicate this procedure as well as teach children about absorption by getting the children involved in coloring their own flowers and watching the colors change.
Use a white flower, such as a carnation, and a celery stalk that still has leaves. Cut the end of the stems. Fill two cups with water; add a few drops of two different food coloring, one in each cup. Place the flower in one cup and the celery stalk in the other. Before the end of class, the carnation begins to absorb the food coloring until it reaches the flower or leaves. When the children return the following morning, the flower will have the same color as the food coloring. Once the process is complete, cut a slit into the celery stalk. The children will see the food coloring in the holes of the stem showing them plants not only get their water from the air, but from the ground as well.
Creating volcanic eruptions in school is a common experiment because it's fun, easy and a learning experience. It's a good idea to do this experiment outdoors as it is messy.
Find a small plastic bottle, such as a 20-ounce soda bottle with a loose-fitting cap or a cork and fill the bottle halfway with common white vinegar. Color the vinegar with a little red food coloring to make the lava look real. Use clay or modeling compound and build a mountain around the bottle for a realistic effect. Use 1 tablespoon of baking soda and wrap it in tissue paper. Secure the ends of the paper with pieces of string. Quickly drop the baking soda in the bottle and just set the cap on the bottle. Almost instantly, the volcano will explode sending the cap high into the air.
Many elementary school science fairs have this interesting substance, which is a liquid and a solid in one and perfect fun for preschoolers.
In a large container, such as a plastic bowl, fill with 1/2 cup water and 1 cup of corn flour. Use a wooden spoon and stir. To show the children how this object is a liquid, stir slowly and tip the bowl to let it drip. After dripping the slime, stir quickly, which allows it to harden; have the children punch it to show the liquid is now a solid.
Stirring the mixture quickly allows the molecules of the corn flour to harden because the water can't get through it quickly. Stirring slowly, water can slide over the corn flour easier making it a liquid. This slime acts the same way as quicksand because quicksand is just regular sand that's so saturated with water that it reduces any friction between the sand particles.
This is a great experiment because you can actually play with it. Use two containers, one smaller than the other. In the larger container, fill the bottom with PVA glue, or school glue, but not Elmer's glue. Place two or three drops of water in the container and mix. Add two or three drops of food coloring and stir again. Add a little borax or powdered laundry detergent and mix. Place this mixture into the smaller container and you will have some silicone polymer to play with.