Worked example 1
An apple is quite heavy. Why does it float?
- Apples contain lots of air pockets.
- So their density is less than water's.
- Less dense than water → floats.
Answer: Its density is lower than water's because of trapped air.
Science · Foundation
Float or sink? A simple density experiment at home
Whether an object floats depends on density — how much mass is packed into its size — compared with water. This experiment teaches predicting, testing and explaining.
- 1Learn it
- 2See it worked
- 3Try it online
- 4Print it
- 5Check your answer
Before you start
Who it's for and what to know first
None. Needs a bowl of water, a towel and small objects (coin, apple, cork, plastic toy, pebble, dry pasta). An adult should supervise near water.
Learn it
How it works
- Predict first: write ‘float’ or ‘sink’ for each object before testing.
- Fair test: use the same bowl and water for every object and place each gently on the surface.
- Objects less dense than water float (cork, apple). Objects more dense sink (coin, pebble).
- Shape matters: a ball of foil sinks but the same foil shaped as a boat can float, because it pushes aside more water.
- Safety: never leave young children alone with water, and wipe up spills.
Try it online · print it · check it
Practice questions
Tips
Common mistakes
- Saying ‘heavy things sink’. A large ship is heavy but floats — it is about density and shape.
- Changing more than one thing at once (object and liquid), so you cannot tell what caused the result.
Last reviewed: 25 September 2026