TinyStepper
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Sink or Float Bath Lab

Drop household items into the bath and predict together — will it sink or float? Simple science at bath time.

Activity details

2y–4y10 minslowindoorPlastic CupsSpongesSpoons (Metal)

Instructions

Get ready
  • Gather 5-6 household items of different weights and materials
  • Bring them to the bath in a small container
  1. Gather 5-6 household items of different weights and materials
  2. Bring them to the bath in a small container
  3. Hold up the first item: 'This is a sponge. Will it sink or float?'
  4. Let your toddler make a prediction — thumbs up for float, thumbs down for sink
  5. Drop it in together and watch: 'It floats! Were you right?'
  6. Try the next item — mix easy and surprising ones
  7. After testing everything, let your toddler experiment freely: pushing floaters down, stacking sinkers

Parent tip

Set out plastic cups and sponges before inviting your toddler in so the first minute feels smooth.

Toddler sitting back from a sensory tray looking calm and satisfied after focused play

What success looks like

Watch for focused exploration — fingers digging in, pouring back and forth, or sorting by feel. Even a few minutes of this builds concentration.

Gather a few household items — a sponge, a metal spoon, a rubber duck, a plastic cup — and bring them to the bath. Before dropping each one in, ask your toddler: 'What do you think — will it sink or float?' Drop it in and watch together. The surprise of a heavy-looking sponge floating or a small coin sinking sparks genuine curiosity. It's simple science in a space your toddler is already in, turning bath time from a chore into an experiment.

Why it helps

The NHS Best Start in Life programme identifies play as essential for cognitive development, supporting thinking, concentrating, problem-solving and decision-making. Prediction and observation are foundational scientific thinking skills. When toddlers guess and then check, they're practising hypothesis testing — the basis of all inquiry-based learning. The hands-on, sensory-rich environment of the bath makes abstract concepts like density and buoyancy concrete and memorable. It also extends bath time naturally, which is helpful when you need a few extra minutes.

Variations

  • Sort the items into two piles after testing: 'sinkers' and 'floaters.'
  • Try the same item in different forms — a flat piece of foil vs a scrunched ball.
  • Use bath toys your toddler already has and predict which will float.

Safety tips

  • Only use items that are too large to be a choking hazard.
  • Avoid glass, sharp metal, or anything that could break in water.
  • Supervise closely — never leave your toddler unattended in the bath, even briefly.

Want to try another?

Bath Time Colour Mixing Lab

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