Changes of State
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When a substance changes state, the number of molecules in that substance doesn’t change and so
neither does its mass.
The only thing that changes is its energy
In a solid:
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The molecules are very close together and arranged in a regular pattern
The molecules vibrate about fixed positions
• In a liquid:
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The molecules are still close together (no gaps) but are no longer arranged in a regular pattern
The molecules are able to slide past each other
• In a gas:
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The molecules are widely separated - about 10 times further apart in each direction
The molecules move about randomly at high speeds
There are five changes of state that can occur between solids, liquids and gases:
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Melting - When a solid turns into a liquid (e.g. ice to water)
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Boiling - When a liquid turns into a gas (evaporating)
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Condensing - When a gas turns into a liquid
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Freezing - When a liquid turns into a solid
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Subliming -When a solid turns into a gas
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