Gases and Vapours

Understanding Gases and Vapours

  • Gases are one of the four fundamental states of matter with particles that have neither defined volume nor defined shape.
  • Vapours, on the other hand, are created when substances are heated and become gaseous but below their critical temperature.

Properties of Gases and Vapours

  • Gases and vapours expand infinitely. This means that when placed in a container, they will expand to fill all available spaces.
  • Their particles move freely and randomly, often colliding with each other and the walls of the container — these collisions cause pressure.
  • In gases and vapours, the space between particles is far greater than the size of the particles themselves.
  • They are compressible, and their density is usually less than that of liquids or solids.
  • Boyle’s Law states that the pressure of a given amount of gas ‌held at a constant temperature varies inversely with the volume: P1V1 = P2V2.

Applications in Cryogenics and Vacuum Technology

  • In cryogenics, gases play an essential role in cooling systems. For example, helium gas is used in super cooling because of its low boiling and melting points.
  • Vacuum systems often use gases and vapours to create a vacuum environment. This can be used for experimental purposes or in industries for tasks that require the absence of air or other gases.
  • Understanding the behaviour of gases and vapours under different temperatures and pressures is crucial for proper equipment and system design in cryogenics and vacuum technology.