Solids, Liquids & Gases (Edexcel GCSE Physics)

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Solids, Liquids & Gases

  • Matter can exist in one of three different states: solid, liquid, or gas

Solids

  • In a solid:
    • The particles are closely packed
    • The particles vibrate about fixed positions

  • Solids have:
    • A definite shape (they are rigid)
    • A definite volume

Liquids

  • In a liquid:
    • The particles are closely packed
    • The particles can flow over one another

  • Liquids have:
    • No definite shape – they are able to flow and will take the shape of a container
    • A definite volume

Gases

  • In a gas:
    • The particles are far apart
    • The particles move randomly

  • Gases have:
    • No definite shape – they will take the shape of their container
    • No fixed volume – if placed in an evacuated container they will expand to fill the container

  • Gases are highly compressible, this is because:
    • There are large gaps between the particles
    • It is easier to push the particles closer together than in solids or liquids

Shape and volume, IGCSE & GCSE Physics revision notes

Diagram showing the three states of matter in terms of shape and volume

Solid, Liquid, Gas Summary Table

Differences in Density

Solids & Liquids

  • In solids and liquids, the molecules are tightly packed together
    • The difference is, in a liquid, the molecules have enough energy to push past each other

  • As a result of this, the density of solids and liquids are roughly the same

solid-liquid-density, IGCSE & GCSE Physics revision notes

The molecules in solids and liquids are tightly packed, giving them a high density

Gases

  • In a gas, the molecules are widely separated
    • As a result of this, gases have significantly lower densities than solids or liquids

  • At room temperature, the distance between molecules in a gas is roughly ten times (in each direction) the distance between molecules in a solid or liquid
  • As a result, the density of a gas is typically around one-thousandth (1/1000) of the density of a solid or liquid, for example:
    • The density of water is 1000 kg/m3
    • The density of air at sea level and room temperature is 1.3 kg/m3

Gas Density, downloadable IGCSE & GCSE Physics revision notes

The molecules in a gas are widely spaced, giving it a much lower density

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Ashika

Author: Ashika

Expertise: Physics Project Lead

Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.