Changes in state

When a solid item is heated the forces of attraction between the particles become weaker

as a result the particles move more quickly

• The particles gain more kinetic energy
• the solid item melts
• the particles move from their fixed positions
• as a result the solid changes into a liquid
• this process is known as melting
• if the liquid is heated further the particles move faster and apart from each other
• the liquid turns into a gas
• That is the liquid vapourises
• if heat is removed and the gas is allowed to cool it condenses
• the particles move closer together and move more slowly and thus the gas turns into a liquid
• if the liquid is cooled further it solidifies
• that is it turns into a solid
• the particles in a solid have less kinetic energy
• they thus move less because the forces of attraction between them is stronger
• solidifaction-is when a liquid turns into a solid
• vapourisation-when a liquid turns into a gas
• condensation-is when a gas turns into a liquid
• melting-is when a solid turns into a liquid

sublimation

Dry ice subliming. Image credit MediaWiki

• when some solids are heated they do not melt
• instead they turn into a vapour immediately without turning into liquid first
• for example when gray iodine crystals are heated they turn into a purple vapour
• this is known as sublimation
• sublimation-is when a solid turns directly into a vapour

To access more topics go to the Combined Science Notes page.