Temperature – Level 3 Applied Science BTEC Revision

Understanding Temperature

Temperature is a measure of the average kinetic energy of particles within a substance.
It’s a fundamental component of understanding how cryogenics and vacuum technology works because it influences the behaviours of gases and vapours to a great extent.
Changes in temperature can cause a change of state in substances, from solid to liquid (melting), liquid to gas (boiling) or solid to gas (sublimation).
We usually measure temperature using the units degrees Celsius (°C), kelvin (K), or degrees Fahrenheit (°F).

Raise in temperature generally increases the volume of a substance. This is due to the increase in kinetic energy causing particles to move more and take up extra space.
The temperature of a substance is directly related to its pressure — as temperature increases, so does pressure.
Pressure and volume also have a relationship with temperature, often expressed by Gay-Lussac’s Law: the pressure of a gas at constant volume is directly proportional to the temperature, usually written as P1/T1 = P2/T2.

Cryogenics is the study of how materials behave at very low temperatures, generally below -150 degrees Celsius.
Understanding temperature is crucial in cryogenics as reductions in temperature can change material properties, such as resistance to electricity and thermal capacity.
One of the main uses of cryogenics is in the production of liquified gases, such as helium and nitrogen.
A cryocooler is a device used to achieve low temperatures. It works by extracting heat from a system and expelling it to an area of higher temperature.

In vacuum technology, having control over temperature is crucial as it affects the rate of outgassing — the process where trapped gases are released from materials within the vacuum chamber.
A vacuum is a space where the pressure is significantly below atmospheric pressure, and this causes substances to boil at much lower temperatures than they usually would at standard pressure.
Temperature control is essential for maintaining the integrity of a vacuum system. For instance, high temperatures could cause components to fail, whilst low temperatures could cause unwanted condensation.