Water is free, making it an easy material for impromptu science experiments. Through a series of simple experiments, preschoolers can learn the various ways that water exists. First they can explore the idea of water as they know it, as a liquid. Liquid water goes in a cup. You can drink it, it can spill out of a container, it can make things wet.
When you put water in a freezer, however, you change it into ice. Ice still goes in a cup but it holds a solid shape of its own and will not spill the way liquid water does. If you heat water it becomes a gas, evaporates into the air, and has no shape at all. Children can learn how heat and cold affect water through these simple tasks.
A simple lesson in life science comes from a series of experiments with plants. Give preschoolers three of the same type of seed or plant. A bean sprout works well for this experiment since they can see the green shoots of the plant relatively soon. The students plant the bean sprouts in soil inside small styrofoam cups or plant pots and wait two weeks or so for a sprout to appear, then they can begin their science experiments.
Students place one plant in full sunlight, one in partial sunlight, and one in the dark. Over the next few weeks they track changes in the plants by measuring them and coloring pictures to represent the plant's overall shape and color to see the effect of sunlight on plants. For a similar idea, they can try to use two of the same plant but feed them differently or water them differently to see how water affects a plant.
Cooking is a science activity in and of itself. In order to cook you have to combine ingredients, change the properties of something by mixing it with something else, and sometimes add heat or cold in order to complete its preparation. Have kids practice with simple recipes to participate in science laboratory activities in the kitchen.
Have them mix up a batch of cookie dough and see how the flour, sugar, and other dry ingredients combine with the liquid ingredients and how heat turns sticky batter into a cookie or cake.
They can make their own ice cream and wait for the cold of the freezer to transform their liquid milk creations into a semisolid frozen treat.
Students love to sculpt with modeling compound, so making their own can become an experiment that has creative results. Students and teachers work together to mix the ingredients: flour, salt, cream of tartar, oil, and boiling water. Then students can use a variety of options for coloring the dough, from powdered drink mixes to natural substances like tea or beetroot or even just food coloring. Have them record their observations about the coloring process.
For a new spin on the idea, challenge students to predict the color the play dough will turn out to be if they mix together two primary colors or other color combinations. Have them use crayons to scribble out a sample color and the student whose guess most closely matches the actual result wins a prize.