Pumpkin Science: To Float or Not to Float? Activity

2.8 based on 14 ratings
Updated on Oct 11, 2012

In kindergarten, young scientists make lots of predictions. Not only is it a core science curriculum skill, but it can also be downright fun when it’s tied into seasonal adventures. And fall is as great a time as any to be a scientist. But this experiment can be done any time of the year. Here's a great activity about exploratory science that challenges your child to make predictions and discover relative size, density, and buoyancy with... pumpkins!

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 you local pumpkin patch or grocery store.
  3. Observe the pumpkins. Ask your child to make a some educated guesses about the size of the pumpkins: for instance, does he think his head is smaller, the same size, or larger than the pumpkin you are holding?
  4. Find different-sized pumpkins and have him make that comparison again. Then use the string you measured earlier to discover whether your child 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 he thinks it will float or sink. Why does he 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.

Erin Zlatunich, M.A. Curriculum and Instruction, is a kindergarten teacher in Millbrae, California. She is also the mother of two small children.

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