A r c h i v e d  I n f o r m a t i o n


We don't usually stop to wonder why a big cruise ship can float as well as a feather. This activity helps to explain.

What you'll need

1 solid wood building block
1 plastic cap from a bottle
2 pieces of aluminum foil (heavy duty if you have it)
1 chunk of clay

Grown-up alert!

1 pair of pliers
1 bathtub (or sink) filled with water
Your science journal

What to do

  1. Hold the wood block in one hand and the plastic cap in the other hand.

    Which one feels heavier?
    Do you think the wooden block will float, or will it sink?
    Will the plastic cap float, or sink?

  2. Put both of them on the water to test your predictions. What happens? Put both of them under the water. What happens now?

  3. Take a piece of aluminum foil and squeeze it into a solid ball with the pliers. Drop it in the water. Does it float or sink?

  4. Get another piece the same size and shape it into a little boat. Place it on top of the water. Does it float now?

  5. Try the same experiment with clay. Make a ball and drop it in the water. What happens?

  6. Shape the clay into a boat and put it on the water. Does it float now?
The clay and foil balls sink because they are squeezed into small shapes, and only a small amount of water is trying to hold up the weight. When you spread out the clay or foil, it floats because the weight is supported by a lot more water.

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