JAMB - Chemistry (1995 - No. 7)
A liquid begins to boil when?
its vapour pressure is equal to the vapour pressure of its solid at the given temperature
molecules start escaping from its surface
its vapour pressure equals the atmosphere pressure
its volume is sightly increased
Paliwanag
The normal boiling point is the temperature at which the vapour pressure is equal to the standard sea-level atmospheric pressure.