CIE IGCSE Physics

Revision Notes

2.1.2 Molecular Matter

Arrangement & Motion of Molecules

Solids liquids gases, IGCSE & GCSE Physics revision notes

Diagram showing the arrangement and motion of different states of matter 

  • In a solid:
    • The molecules are very close together and arranged in a regular pattern
    • The molecules vibrate about fixed positions
  • In a liquid:
    • 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:
    • The molecules are widely separated – about 10 times further apart in each direction
    • The molecules move about randomly at high speeds

 

Extended Only

The Forces & Distances between Molecules

  • In a solid:
    • The molecules are held in place by strong intermolecular bonds
    • These bonds prevent the molecules from moving, giving the solid its rigid shape and fixed volume
  • In a liquid:
    • The molecules have enough energy that they are able to break the bonds between them
    • The bonds are still there, but they no longer hold the molecules in place
    • As a result, the molecules can move around (by sliding past each other) allowing the liquid to flow
  • In a gas:
    • The molecules are now moving around randomly at high speeds
    • The molecules have broken the bonds between them: They are widely separated with no long-range forces binding them together
    • As a result the molecules are able to move freely and so the gas can flow freely
    • Because of the large spaces between the molecules (along with the absence of long-range forces) the gas can easily be compressed and is also able to expand

 

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Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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