Sculpt a two foot hallowed out volcano with sand or dirt. Use a spray bottle with water to help you mold it. Form ridges and paths on the volcano for lava to travel down. Place a plastic cup on the inside of the volcano. Add baking soda and 4 drops of red food coloring to the cup. When you are ready to make the volcano erupt, add 1/4 cup of vinegar to the cup and watch the explosion. Make sure to place the volcano in a spot where it won't create a huge mess. Have the kindergartners draw a volcano on a poster board with some information about how they work.
Explore your back yard or a park for materials to make a bird nest. Tell the kindergartners to pretend they are birds and ask them to make their own bird nest. You can gather grass, sticks, leaves and anything else you can find. Look at any bird nests you encounter for ideas. Bring all the materials back and place them on a newspaper. Have the kindergartners pretend they are bird and use just two fingers to build the house, simulating a bird's beak. Weave the materials together best as possible to form a sturdy bird nest. Have the children draw a picture of the nest, a bird family and the materials used on a poster board.
Grab two packs of Mentos, a 2L bottle of Diet Coke and 2 to 3 other 2L bottles of other carbonated sodas. Stand up the bottle of Diet Coke in an open field and open the top. Protect your eyes, quickly drop 2 to 4 Mentos into the bottle and run at least 20 feet away. Make sure no one is standing close to the bottle. The Mentos and carbonated soda react to violently shoot foam out of the bottle and into the air. See which soda brands have the strongest reaction and how it affects the reaction to use less or more Mentos.
Soak a cup of sunflower seeds in water overnight. Fill a gardening tray with dirt, spread the seeds around and place a damp paper towel over them. Water the seeds whenever the paper towel dries out. Once sprouts push through, remove the paper towel and move the tray in front of a window with sunlight. After a week, pull out one of the plants and show the kindergartners the leaves, stems and roots. Have the children draw the different parts of the plant on a poster board.