Float my boat...

What things float and what things sink is such a natural question for kids - even at very young ages. This presents a wonderful opportunity to practice being a scientist at bath time. Take a second and ask you kids to make a prediction about what floats and what sinks. Test your predictions and follow up with seeing if you were right.

During our Messy Fingers session yesterday, we made predictions about floaters and sinkers. We had a few surprises. A few objects floated at first on the surface of the water and then sank. They were held up by the surface tension of the water. Crayons were another surprise. I expected that since they are made of wax that they would float, but regular crayons sank. Fat crayons, even more surprisingly, neither sank or floated but hovered in the middle. One end floated more than the other. Cool.

We made boats out of tin foil and modeling clay. Our foil boats were modified by reshaping and adding floaties so they were strong enough to hold a ball of clay. This was quite a production. Both rectangular and canoe-shaped boats worked really well for this.

One mom wondered why I chose to use modeling clay rather than play dough to use in the water. I gave her some play dough to test out and it falls apart in the water (so it is washable!).

If you want to play with some other floating and sinking ideas, check out the ideas below:

Make a soap boat – cut a small boat from cardboard or foam. Leave a notch in the end. Float this in a pan of water. Does the boat float? Can you make it move? Put a tiny sliver of soap or a dot of liquid soap in the notch. What happens? Does this work in the tub? [This won’t work in the tub if you’ve used any soap. The boat floats on the surface tension of the water. Soap breaks up the tension.]

Flinkers – can you find an object that neither floats or sinks?

Fish – check out some fish. Either in your own aquarium or visit a local pet shop. How do they move? What shapes are they? Does their shape affect how they move? Can you move like the fish?

Jello - Make your own aquarium – make up some blue jello and as it solidifies, add some gummy sharks or fish. Make a prediction about how long it will take to solidify. Why don’t they float up to the top? Watch the jello as it solidifies. How long does it take?

For some other great boat activities, click here.