Floating and Sinking – 2nd Class




Energy and forces

Strand unit



The child should be enabled to:

  • Investigate how forces act on objects.
  • Investigate floating and sinking with a range of materials and objects.
  • Make and test predictions about objects that will sink or float. Group objects that will sink or float.
  • Investigate how some objects may be made to float by hollowing them out


Questioning how things stay afloat. Why do some objects float and some sink?
Observing what happens as they investigate.
Experimenting with different objects
Recognising patterns in investigations.
Recording the information and communicating it to others

Designing and making

  • Exploring
  • Planning
  • Making
  • Evaluating

Integration with Maths

Measuring the amount water going into the basin, recognising 3-D shapes, fractions; cutting fruit into equal parts, using a tally to count predictions.

First we investigated making an object sink.

Our Predictions

9 children predicted the orange would sink.
14 children predicted the orange would float.

How could we make the orange sink? Some ideas we came up included

  • Adding more water to the basin.
  • Cutting the orange in half.
  • Peeling the orange.
  • Pushing down on the orange.

We investigated our ideas. We made predictions.


Adding more water – the orange stayed afloat.
Cutting the orange in half – still the orange floated.
Pushing down on the orange – it stayed at the bottom while we held it there but
floated back to the top when we let go.
Peeling the orange – It finally sank!

Next we investigated making an object float. We each made a sphere out of some plasticine. We made passengers from paperclips.

Our Predictions

15 children predicted the spherical boat would sink.
8 children predicted the spherical boat would float.

We explored how we might make the plasticine boat float. We experimented and tried out our ideas.

Some boats floated on the first try. Some boats needed some evaluating and adjusting. We had to make sure there were no leaks or the boat would sink.

We learned that the shape of a boat affects the weight (passengers/cargo) it can hold.The more water a boat displaces, the more it will float and the more weight it can take.


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