Changes in State: Melting and Freezing

Changes in State

• Sublimation is a process where a solid changes directly to a gas or vice versa, without going through the liquid phase.

Melting and Freezing

• A pure substance melts at a specific temperature, known as the melting point (m.p).
• The melting point is the same temperature at which a liquid freezes, known as the freezing point (f.p).
• The melting and freezing points of a substance are always the same temperature.
• For example, pure water melts and freezes at 0°C.

Changes of Physical State

• Large changes in temperature and pressure can cause a substance to change its physical state.
• The changes between solid, liquid, and gas states can occur by raising or lowering the temperature of the substance at atmospheric pressure.

Melting and Boiling Points

• The melting point (m.p) is the temperature at which a solid turns into a liquid.
• The boiling point (b.p) is the temperature at which a liquid turns into a gas.
• The melting point and freezing point have the same value, while the boiling point is a separate value for a substance.