Float or Sink?

Level: K - 1

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The clay and foil balls sink because they are squeezed into small shapes and only a small amount ofwater is trying to hold up the weight.When the clay or foil is spread out, it floats because the weight is supported by a lot more water.

What You Need

• 1 block of solid wood
• 1 plastic bottle cap
• 2 pieces of heavy-duty aluminum foil
• 1 piece of modeling clay
• Sink filled with water

What to Do

• Tell your child to hold the wood block in one hand and the plastic cap in the other hand. Ask him to answer the following questions:

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

• Have your child test his predictions by carefully placing the block of wood and the cap on the water. What happens? Next, have him put both under the water. What happens now?

• Give him a piece of aluminum foil and tell him to squeeze it tightly into solid ball then drop it in the water. Does it float or sink? Give him another piece of foil. Help him to shape it into a little boat, then have him carefully place it on top of the water. Does the foil float now?

• Help him to try the same experiment with the clay. Have him make ball and drop it in the water. What happens? Then have him shape the clay into a boat and put it on the water. Does it float now?

Source: U.S. Department of Education, Office of Communications and Outreach, "Helping Your Child Learn Science," Washington, D.C., 2005

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