GCSE Physics (AQA)

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Gases

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Particle model of matter Changes of state and the particle model

Gases

3:50 Density and States of Matter
Spec 4.3.1.1
  • Gas is a state of matter where atoms or molecules move freely with large distances between them.
  • In the gas state, molecules are not in contact, unlike solid and liquid states.
  • Gas molecules move independently and spread out around a container.
  • Large distances between gas molecules are due to weak intermolecular forces.
  • Bonds between gas molecules are almost non-existent, allowing them to move freely.
  • Gas molecules are in constant random motion due to kinetic energy.
  • At absolute zero, gas molecules theoretically stop moving.
  • Random motion means molecules move in random directions and speeds.
  • Molecules can travel in any direction in three dimensions and change speeds and directions upon collision.
  • Gas expands to fill any container, matching the shape of the space they occupy.
  • Gas molecules spread out to fill a container, moving away from each other.
  • Gases can move upward as they are less affected by gravity.
  • Gas can be compressed by bringing molecules closer together due to the empty space between them.
  • Compression reduces the volume of the container but not the number of gas molecules.
  • Compressing a gas changes its properties, but further details are learned elsewhere.
  • Understanding gas motion and container size is important for exams.

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