1.1 Solids, liquids and gases

2026 Syllabus Objectives

  1. Core: State the distinguishing properties of solids, liquids and gases
  2. Core: Describe the structures of solids, liquids and gases in terms of particle separation, arrangement and motion
  3. Core: Describe changes of state in terms of melting, boiling, evaporating, freezing and condensing
  4. Core: Describe the effects of temperature and pressure on the volume of a gas
  5. Supplement: Explain changes of state in terms of kinetic particle theory, including the interpretation of heating and cooling curves
  6. Supplement: Explain, in terms of kinetic particle theory, the effects of temperature and pressure on the volume of a gas

Matter and Its Nature

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Matter is anything that occupies space and has mass. It encompasses all substances and materials of which the universe is composed. Chemistry studies how matter behaves and changes under different conditions.

🔑 Key Definition: Matter consists of very small particles such as atoms, molecules, or ions. These particles are in constant motion and their arrangement determines the physical state of matter.

The Three States of Matter

Matter exists in three physical states depending on the conditions of temperature and pressure:

  • Solid
  • Liquid
  • Gas

Liquids and gases are collectively called fluids because they have the ability to flow.

Properties of Solids, Liquids and Gases

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Physical Properties Comparison

Physical StateVolumeDensityShapeFluidity
SolidHas a fixed volumeHighHas a definite shapeDoes not flow
LiquidHas a fixed volumeModerate to highNo definite shape - takes the shape of the containerGenerally flows easily
GasNo fixed volume - expands to fill the containerLowNo definite shape - takes the shape of the containerFlows easily

Detailed Description of Each State

Solids:

  • Have a fixed volume and fixed shape
  • Have high density due to closely packed particles
  • Particles are arranged in a regular pattern (lattice structure)
  • Particles vibrate in fixed positions but cannot change location
  • Cannot be compressed easily

Liquids:

  • Have a fixed volume but no fixed shape
  • Take the shape of their container
  • Have moderate to high density (generally less dense than solids, except water)
  • Particles are close together but arranged randomly
  • Particles can move and slide past each other, enabling flow
  • Cannot be compressed easily

Gases:

  • Have no fixed volume and no fixed shape
  • Expand to fill any container completely
  • Have very low density due to large spaces between particles
  • Particles are far apart and move randomly and quickly (approximately 500 m/s)
  • Particles collide with each other and with container walls, creating pressure
  • Can be easily compressed due to large intermolecular spaces

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