Experiment 1 — Float or Sink?

Topic: Physics · Classes 4–5 · Materials around us: floating and sinking

Aim: Make the lump of clay float on water. (Clay sinks — so you will have to think!)

Daily: Ships made of thousands of tonnes of steel float across the ocean, while a steel spoon sinks in your kitchen sink. Fishermen in Kerala and Odisha shape their boats wide and hollow for exactly this reason.

Question: A lump of clay sinks. If you flatten the same clay into a boat shape, what will happen?

Exp: The material has not changed, but the shape has. A boat shape displaces much more water, and that is what decides floating.

Question: A steel ship floats but a steel nail sinks. Why?

Exp: The hollow hull displaces a huge weight of water.

Question: An egg floats in very salty water because…

Exp: Salt increases the density of the water so it can support the egg.

Question: In a fair test of floating, what must stay the same?

Exp: Change only the object; keep everything else identical.

Question: Which floats because it contains trapped air?

Exp: The trapped air makes it very light for its size.