At the boiling point, a liquid changes to a gas throughout its volume, with bubbles of vapour forming within the liquid. The temperature remains constant during boiling because the energy supplied is used to break intermolecular bonds rather than increase kinetic energy.
The boiling point depends on the external pressure. Higher pressure raises the boiling point; lower pressure lowers it. Water boils at 100 C at standard atmospheric pressure.
Boiling differs from evaporation, which occurs only at the surface and at any temperature below the boiling point.
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