1. STATES OF MATTER
Melting, Freezing, Evaporation & boiling, Condensation and
• Change from a solid to a lquid
• A substance melts at 0 ̊C
• The melting point of a substance is fixed in pure substances.
• Impure substances have a variable melting point.
• When heat is applied, the particles are pushed apart.
• The temperature remains at 0 until all of the solid substance is
• Example : When a ice turns to water.
• The change from a liquid to a solid.
• The temperature at which when a liquid freezes is called the “freezing
• For most substances, the “freezing point” is the same as the “melting
4. Evaporation & Boiling
• Evaporation is the process in which particles of a liquid leave the
surface of the liquid as a vapour.
• When a liquid is heated, the particles move faster and collide with
each other. When the particles acquire sufficient energy, they break
free of the surface and escape.
The rate of evaporation depends on:
• The nature of the liquid
• The temperature
• The amount of exposed surface
5. Evaporation & Boiling
• Boiling is the process by which a liquid is freely converted to a gas or
• When a substance is heated, the temperature rises until it reaches
the boiling point.
• When boiling has started, the temperature remains steady.
• Evaporation takes place at the surface, but boiling takes place
throughout the liquid.
• The change from a gas to a liquid.
• It can be accomplished by: cooling for some gases(e.g. water vapour)
or a combination of cooling an compression (e.g. propane).
• The particles lose energy and move closer together as the gas cools
therefore increasing the attraction between them.
• When a substance changes directly from a solid to a gas or gas to
liquid without going through the liquid state. (examples of substances
that sublime are iodine and ammonium chloride)
8. Rate of Diffusion
• Solids -> Very Slow
• Liquids -> Slow
• Gases -> Rapid
9. END OF PRESENTATION