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Science

Sink or Float?

Overview

Children make predictions about which objects will sink or float, then test them in water and discuss what they find.

Learning Objective
Children predict and test whether objects sink or float, beginning to notice patterns in their results.

Resources needed

  • Container of water (bucket, bowl, or puddle)
  • A variety of small objects: stone, leaf, stick, bottle cap, cloth, seed

Lesson stages

0 / 7 done
  1. 1 Show the container of water and the objects.
  2. 2 Hold up each object and ask: will this sink or float? Children predict with thumbs up or down.
  3. 3 One child places the object in the water — observe what happens.
  4. 4 Record results in two groups: sinkers and floaters.
  5. 5 After all objects: look at the two groups — what do sinkers have in common? What about floaters?
  6. 6 Ask: can you make a sinker float? Try with a leaf folded into a boat shape.
  7. 7 Ask: does the size always predict? Try a large leaf vs a small stone.

Tap a step to mark it as done.

Variations

  • Try the same material in different amounts — does more weight always sink?
  • Make a simple boat from a leaf or bark and load it with stones.
  • Try salt water vs plain water for some objects.
More information

Teach: sink, float, predict, heavy, light, surface, water. The predict-test-observe cycle is the scientific method in its simplest form — name each step clearly.

Let children who are shy about predicting simply observe and describe first. Reduce the number of objects to five for younger children.

Can children make a prediction before testing? Can they notice that heavy objects tend to sink but identify at least one exception?

Use any available water source and natural objects. No specialist equipment needed at all.

Children initially predict that heavy objects always sink and light objects always float. The leaf-boat experiment — a heavy stone floating inside it — powerfully challenges this assumption.

Sink or float introduces prediction, testing, and pattern-finding in a concrete, engaging context. It also introduces the concept of density intuitively.

Activity details
Early Years Easy 20 minutes 5 minutes prep Small Group, Whole Class Indoor & Outdoor
Topics
Floating And Sinking Prediction Materials