P6 Molecules and matter

boiling point

Temperature at which a pure substance boils or condenses

density

Mass per unit volume of a substance

freezing point

The temperature at which a pure substance freezes

internal energy

Energy of the particles of a substance due to their individual motion and positions

latent heat

Energy transferred to or from a substance when it changes its state

melting point

Temperature at which a pure substance melts or freezes (solidifies)

physical change

A change in which no new substances are produced

pressure

Force per unit cross-sectional area for a force acting on a surface at right angles to the surface. The unit of pressure is the pascal (Pa) or newton per square metre (N/m2)

specific latent heat of fusion Lf

Energy needed to melt 1 kg of a substance with no change of temperature

specific latent heat of vaporisation Lv

Energy needed to boil away 1 kg of a substance with no change of temperature