Sink or Float Science Experiment

A large clear container or plastic tub, half-filled with water

8-10 test objects: wooden block, rock, cork, coin, sponge, plastic lid, metal spoon, leaf, grape, rubber duck

A towel for underneath

Set up the water tub on a towel. Gather your test objects.

Hold up the first object: "Will this wooden block sink or float? What do you think?"

Let your toddler drop it in. Watch together: "It floats! It stays on top!"

Try the next object: "How about this coin? Sink or float?"

Continue through all objects. Separate sinkers and floaters on towels.

Review at the end: "Look at the floaters. What do you notice about them?"

Let your toddler re-test favorites. Repetition reinforces the concept.

A clear container lets your toddler watch sinkers go all the way to the bottom. Opaque tubs hide the action.

Don't explain density. At this age, the concept is simply: some things float, some don't. The "why" comes later.

Include some surprising items — a heavy orange floats, but a grape sinks. Surprises make the activity memorable.

Let your toddler add their own objects. Their choices tell you what they're curious about.

Try this in the bathtub for an easy cleanup option.