Pumpkin Science: To Float or Not to Float?

What You Need:

  • Piece of string about the length of your arm
  • 3 different sized pumpkins
  • Scissors
  • Bath tub of water or large bucket filled with water

What You Do:

  1. Use the string to measure the size of your child’s head, then cut it.
  2. Go to your local pumpkin patch or grocery store.
  3. Observe the pumpkins. Ask your child to make some educated guesses about the size of the pumpkins. For instance, does your child think their head is smaller, the same size, or larger than the pumpkin you are holding?
  4. Find different-sized pumpkins and have your child make that comparison again. Then use the string you measured earlier to discover whether they're is correct.
  5. Select your favorite three pumpkins, and bring them home.
  6. Fill your bathtub with water. For this next part, you will be placing the pumpkins in the water, one at a time, to see if they float.
  7. Take one of your pumpkins, and ask your child if they think it will float or sink. Why do they think that? Place the pumpkin in the water and talk about the results.
  8. Repeat Step 7 for each pumpkin, making sure to allow your child to predict what will happen and to discuss the results afterwards.
  9. Discuss with your child why the pumpkins floated regardless of size. (The answer? Pumpkins are hollow objects, and there is enough air trapped in the center of the pumpkin that it floats.)
  10. To extend the activity, get a jack o' lantern to experiment on. Ask your child to predict what would happen if you immersed the jack o' lantern into the water. Now lower the jack o' lantern into the water. What happened? Why did the jack 'o lantern sink? (The answer? The open cuts in the pumpkin let water into the open cavity, which sunk the pumpkin.)

What’s Going On?

For kindergarten students, relative size, density and buoyancy are all huge concepts. It may seem obvious to us, for example, whether a pumpkin is bigger or smaller than someone’s head, or why a pumpkin might float, but for a kindergartener, it can be a revelation. The more fun you can have with all this the better, because without even realizing it, kids are practicing the crucial science skills of measurement, prediction, experimentation, and reasoning.

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