Sink or Float
The easiest science lesson to do with little children is the sink or float lesson. It’s a very visual lesson and once completed, you can leave the water play out for the children to experiment for themselves.
It opens a discussion about suitable materials for boats, children can make predictions and easily see the results of their predictions.
I have done this lesson with children as young as 2 years old. They enjoy the instant nature of the experiments and are able to see which objects sink or float instantly.
picture from myteacherpages.com
I wouldn’t expect children to be writing anything down about this experiment. When I do this experiment, I write a lot of notes about what they children have said, or video their predictions, and take photos of their independent play.