Sink or swim: Materials that are denser than water sink, while materials that are lighter than water float. Assemble a variety of different objects (i.e. a lid from a plastic food container, a pebble, a sponge, a plastic toy, a piece of wood, and a piece of cutlery). Encourage your child to guess whether a particular object will sink or float and to find out for herself what actually happens.
The amazing bathtub hose: Fill a piece of thin plastic tubing with water. Place one end of the tubing in a glass of water and watch as the water is siphoned into the bathtub. Encourage your child to discover what will happen if the end of the hose is held up higher than the glass or if some air is allowed into the tube.
Something from nothing: Empty plastic bottles may appear to have nothing in them, but they are actually full of air. Give your child an empty bottle to hold under water. Ask him to find out what happens if the bottle is held upside down and if it is held upright. Encourage him to guess whether air would escape more quickly from a bottle with a narrower or a wider neck.
An underwater viewer: Make your child an underwater viewer out of an old juice can and a piece of extra-strong plastic wrap. Remove both ends from the can, and stretch the plastic wrap over the bottom. When your child pushes the can through the surface of the water, he will have a clear view of any objects sitting on the bottom of the tub.
Bathtub magic: Stuff a piece of toilet paper into the bottom of a tall glass. Turn the cup upside down and push it through the water until it rests on the bottom of the bathtub. Ask your child to guess whether the the toilet paper is wet or dry.
