Sink or Float Science Experiment
Drop household objects into a tub of water and predict whether they'll sink or float. Your toddler's first real science experiment with a splash of fun.
What You'll Need
- 1Large clear container or plastic tub
- 2Water
- 38-10 test objects (wooden block, rock, cork, coin, sponge, plastic lid, metal spoon, leaf, grape, rubber duck)
- 4Towel
What You'll Need
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
How to Play
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.
Why It Works
Sink or float is the perfect first science experiment because it follows the scientific method in a toddler-friendly way: predict ("what do you think will happen?"), test (drop it in), and observe (watch the result). Your toddler is learning that the world has rules — and they can discover those rules through experimentation.
Tips
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.
Frequently Asked Questions
How long does this activity take?
This activity takes about 20 min, with 5 min of preparation time beforehand.
What materials do I need?
You'll need: large clear container or plastic tub, water, 8-10 test objects (wooden block, rock, cork, coin, sponge, plastic lid, metal spoon, leaf, grape, rubber duck), towel.
What age is this activity for?
This activity is designed for 2-3 years. You can adapt it for younger or older children by adjusting the complexity.
Can this be done indoors or outdoors?
This activity works great both indoors and outdoors, giving you flexibility based on the weather or your space.
How difficult is this activity?
This is an easy activity that requires minimal setup and supervision. Great for busy days or when you need something quick.
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