Fourth-graders study the water cycle. Position a wide-mouth jar on its side. Add a layer of gravel and cover it with charcoal. Put cheesecloth over the charcoal and cover it with dirt. Plant nonflowering plants in the dirt. Water the plants and seal the lid tightly. Use scrap wood to make a wooden frame that will hold the jar, and place the jar in the frame. Set it in a sunny spot, and the entire water cycle will take place. Use pictures or drawings to show the results.
A excellent science fair activity for fourth-graders is a surface tension experiment using milk. Fill a saucer with milk. In the center of the bowl form a triangle with three drops of food coloring using the primary colors: red, yellow and blue. Leave a space between each color. In the center of the drops, add one drop of dish soap. Let it set. As the soap breaks the surface tension, the colors will mix together to form secondary colors.
Determine if sprouts can be grown using different types of liquid, including water. Use the same seeds, alfalfa or bean, for each section of the experiment. Determine how many types of liquid you want to use. Place one or two seeds on each paper towel. Fold the paper towel to form a square. Place the paper towels on different stacks of newspaper. Moisten each paper towel with a different liquid. Keep the paper towel moist for several days, checking to see if the seed has sprouted.
Find out which light bulb will cause the water to evaporate the fastest. Put one saucer of water in four identical boxes and set them away from the window. Pour equal amounts of water in each saucer. In three of the boxes, place lamps with different wattages. In the fourth box, the control box, do not add a light bulb. Leave the bowls, with the lights on, for two days. At the end of the set time, measure the water left in each bowl to determine which light bulb caused the greatest amount of evaporation.