Pumpkin investigation: a 40-minute sink or float science activity, K–2

1. Set the pumpkin in the middle of the rug. Ask: "What do you notice? What do you wonder?" Record a few ideas: color, bumps, stem, lines.
2. Count the lines together. Ask: "Some people say more lines means more seeds. How could a scientist find out?" Keep that question for another day.
3. Measure around the middle. One student wraps yarn around the widest part, another cuts it. Lay the yarn on the floor and ask: "Is it longer than your arm?" Then measure the yarn in cubes.
4. Weigh it. Put the pumpkin on one side of a pan balance and add blocks until it levels. Ask: "How many blocks does our pumpkin weigh?"
5. Predict. Thumbs up for float, thumbs down for sink. Tell a partner why. Tally the votes on the board.
6. Test it. Lower the pumpkin into the water. Most pumpkins float. Ask: "It is heavy, so why does it float?" Guide them to the idea that a pumpkin is hollow, with air inside, and that helps it float.
7. Compare. Test a rock and an apple too, and sort them into floats and sinks.

Fun fact to share: a pumpkin is a fruit, because it grows from a flower and holds seeds, and it is about 90 percent water.

Not celebrating Halloween? Nothing here is about Halloween. Call it a fall pumpkin investigation, or use any squash or a melon.

Differentiation: for younger students, skip the cubes and compare the yarn to their own bodies. For 2nd grade, students measure the yarn in inches and record it. For English learners, post the words float, sink, heavy, light and around with a quick sketch beside each. For students with sensory or motor needs, offer a turn holding the yarn or pressing the balance instead of touching the wet pumpkin, and keep towels close.

Quick check: hold up a small pumpkin and ask, "Will it float or sink? Why do you think so?"

If you try it, tell us how many of your students predicted the pumpkin would sink.