We have been doing some experiments with water, following a nice book that we borrowed from our library: Experimente – Velbi entdeckt das Wasser (experiments about water).
The first one requires a mirror. You put it for some time in the freezer and after you take it out, you breathe on it. The water vapor in your breath condensates on the cold surface of the mirror, so that you can observe water drops on it. No wonder we need to drink all day long: we are constantly loosing water!
A second experiment consists in checking if several items like clothespins and paper clips can float on water. You then try it again, but putting on the water surface one of the layers of a tissue handkerchief. You will see that the lighter items do float now, because they feel a stronger “skin” of the water. It can be a nice moment to explain how some insects can walk on water or how much strength dragonflies need to break this skin in order to lay their eggs inside the water.