Ten kitchen objects go beside a bowl of water. Before each one goes in, everyone calls it: float or sink. Predictions are recorded and then tested one by one. A raw egg, a fresh grape, and a dense potato all behave differently from what common sense suggests — which is reliably the most interesting part.

What you need

large bowl or clean sink
10 objects from the kitchen

How to do it

1Say: "Before each thing goes in the water, guess: float or sink? Then we'll find out."
2Before each object goes in, everyone calls it out loud: float or sink.
3Test them one by one. Mark the correct predictions.
4At the end, ask which one surprised them most. Don't explain yet. Let them wonder.

Variations

Korb-Tür: If they're unsure: "What's your best guess? We're testing it either way."
Ausstieg: The last object goes in. Compare results to predictions. That's the full answer.

💡 Parent tip

A lemon floats. A lime sinks. Same size, similar shape — different density. If you have both: show this first. The difference between two nearly identical objects is the hook that opens the whole investigation.

What your child develops

Density intuition — float or sink depends on density, not size or weight, which challenges what children assume they know
Hypothesis testing — making a prediction before testing is the core scientific method
Calibration — updating beliefs when the result is unexpected is a skill that extends far beyond science