Making lead float

This task is about what makes something float.

Question

Roll of lead
A lump of lead placed in water sinks.
But the same lump of lead rolled out to make a piece of lead foil floats when made into a boat shape.
 
This is because ...

    •  the lead foil is thinner and therefore lighter.

    • air is trapped in the rolled-out lead which makes it buoyant.

    • the boat shape displaces a greater mass of water than the lump of lead.

    • the water's surface tension can support the mass of the thin lead.

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