Gather together a large dishpan and different sized containers (cups, plastic bowls, tupperware).  Using a child's pool, your kitchen sink, or a bathtub, have your child explore how water fills containers. See how many containers of water can fill a larger one.  Or try the reverse:  start with a large container of water and talk about how that water can fill lots of little containers.  Ask, "What do you think will happen if you put your hand in a full bowl of water?  Why does that happen?"  Try putting a sponge in the full container, instead of your hand.  Squeeze the sponge to see how much water comes out.  Try to find different shaped containers (Round, square, rectangular) that hold the same amount of water.

Other Ideas:

• Add a drop or two of food coloring to the water and watch it change colors.  Ask your child to choose a color he/she likes, and ask what two colors need to be mixed to make that color.  See if it works.
• Sink and float game:  Take different items from around the house and have your child guess "What do you think will happen to this when we put it in the water?"  Talk about sinking and floating.  Try a rock, a sponge, a spoon, a straw, an empty water jug, a full water jug.
• At the end, you can add liquid dishwashing soap to the water to make bubbles.

Related Books:

• In a Small, Small Pond by Denise Fleming
• Splash by Ann Jonas
• Who Sank the Boat? by Pamela Allen
• Hundirse y Flotar by Maria Gordon