Float or Sink Test
Drop small household objects one by one into a bowl of water. Predict first: will it float or sink? Test and sort into two groups based on what happens.
- Age3 to 6 years
- Time15 to 30 minutes
- EnergyModerate
- CostFree
- WhereIndoors
- Prep5 min
Gather a handful of small household objects and test them one by one in a bowl of cool water: predicting before each drop, then sorting into floaters and sinkers. Practices prediction and observation through simple hands-on testing.
How to do it
- Fill a large bowl halfway with cool water and set it on a tray or in the sink to catch drips. Gather 8-12 small household objects (spoon, small toy, coin, leaf, cork, small stone, eraser: all at least 3cm for under-4s).
- Before dropping each object, ask "what do you think: will it float or sink?" Listen to their prediction without hinting.
- Drop the object in together and watch. Name what happens: "It's floating: it's staying on top" or "It sank: it went to the bottom."
- Sort the tested objects into two groups on a dry surface nearby: floaters in one pile, sinkers in another.
- After testing everything, look at both groups: "What do the floaters have in common? What about the sinkers?" Accept whatever observations they offer.
What you need
- Large bowl
- Water
- Small household objects
- Tray or towel
- Plates for sorting
Signs it is working
Your child makes a prediction before each test, even if they're often wrong. They notice the result and name it ("it floated!") without prompting. They begin to make a pattern ("I think all the heavy ones sink"), even if the pattern is incomplete or incorrect
If it is not quite clicking
Your child skips predicting and just wants to drop things in: Slow down by holding the object up and asking "what do you think?" before releasing: wait for an answer before dropping. They're frustrated that predictions are wrong: Reframe: "A wrong prediction is the most interesting one: it means there's a surprise!" The sorting into groups doesn't hold their interest: Drop the sorting and just test and observe. Some objects fall in a grey zone (a plastic lid that half-floats): Celebrate the ambiguity: "This one is tricky: what do you think is happening?"
Make it yours
Younger (3y): Focus on just floating vs sinking with 4-5 very obvious objects; skip the sorting step. Older (5-6y), predicting: Ask them to predict the whole set before testing any; tally correct vs wrong predictions. Older (5-6y), extension: Try folding aluminium foil into a boat shape and loading it with small pebbles to see when it sinks. Sibling version: Each person predicts independently and compares predictions before testing
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