There are so many fun and simple science experiements that could be done in a kindergarten class. I think the Magic Milk experienment is a really fun one to do with the class.
1. pour some milk into a bowl (make sure it's either Whole or 2% milk)
2. add a variety drops of food coloring on the milk
3. have a small bowl with dish soap
4. use a Q-tip and dip it in the dish soap
5. have the Q-tip touch the milk
See as the colors are dancing all over the surface of the milk. I remember doing this when I was young.