Gases and Vapours – Level 3 Applied Science BTEC Revision

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.

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.

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.