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States of Matter (Cambridge O Level Physics)

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Dan MG

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Dan MG

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Properties of Solids, Liquids & Gases

  • The three states of matter are solids, liquids and gases

A solid, a liquid and a gas

Shape and volume, IGCSE & GCSE Physics revision notes

The three states of matter in terms of shape and volume

 

Solids

  • Solids have a definite shape and a definite volume
    • Solids cannot flow and are incompressible

Liquids

  • Liquids have no definite shape but do have a definite volume
    • Liquids are able to flow to take the shape of a container but they are incompressible

Gases

  • Gases have no definite shape and no fixed volume
    • Gases can flow to take the shape of their container and are highly compressible

Changes of State

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
  • Changes of state are physical changes and so they are reversible

Melting & Freezing

  • Melting occurs when a solid turns into a liquid (e.g. ice to water)
  • Freezing occurs when a liquid turns into a solid

Boiling & Condensing

  • Boiling occurs when a liquid turns into a gas
    • This is also called evaporating
  • Condensing occurs when a gas turns into a liquid

Diagram of Changes of State

2-1-1-states-of-matter-changes-of-state-cie-igcse-23-rn

Melting and freezing are changes between solid and liquid states, boiling and condensing are changes between liquid and gas states

Examiner Tip

It is very useful to think about water when learning the changes of state, because we are all used to the idea that solid water (ice) melts to become liquid water (water!) and boils to become gaseous water (water vapour).

However do remember that all substances undergo the same changes between the three states, but at different temperatures. So while water will help you to remember the names, don't refer to water in your answers unless it has been specified.

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    Dan MG

    Author: Dan MG

    Expertise: Physics

    Dan graduated with a First-class Masters degree in Physics at Durham University, specialising in cell membrane biophysics. After being awarded an Institute of Physics Teacher Training Scholarship, Dan taught physics in secondary schools in the North of England before moving to SME. Here, he carries on his passion for writing enjoyable physics questions and helping young people to love physics.