CU 3.02Sink and Float
The child places objects in a tub of water and sorts them by whether they sink or float.
Presentation
- 1
Bring the tray to the table. Show the basket and the two small trays.
- 2
Take out the cork, hold it over the water, and lower it gently in.
- 3
Say: 'It stays on top. It floats.' Take it out, dry it, and place it on the float tray.
- 4
Lower the stone in. Say: 'It goes to the bottom. It sinks.' Take it out, dry it, and place it on the sink tray.
- 5
Test each remaining object one at a time, naming the result.
- 6
Invite the child to test the objects again.
- 7
Show how to dry the objects, wipe drips, and empty the water.
Extensions, easiest to hardest
- Predict first: place the object on the tray you think is correct, then test it
- Record results on a sink and float chart with pictures
- Change the shape of a ball of clay into a boat and see whether it floats
- Float an egg in salt water and compare it with fresh water; talk about why people float easily in the Great Salt Lake
Control of error
The water itself: the object stays on top or goes to the bottom.
Ready to move on when the child…
- Names sink or float for each object
- Makes a prediction and checks it
- Completes the work and cleanup independently
Guide note
Marbles and small keys are choking hazards for children who mouth objects; use larger items for them.