Absolute zero
2 marks · EasyExplain why scientists use the Kelvin scale, rather than the Celsius scale, when working with gas laws.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
Also accept: Kelvin scale starts at absolute zero, where particles have zero energy, so calculations involving temperature changes in gas laws are directly proportional and prevent negative values.; In gas laws, the pressure and volume are directly proportional to the Kelvin temperature, not Celsius; using Kelvin gives correct proportionality.
Common mistakes: Because it is easier.; Because Kelvin is a bigger number.
Show mark scheme and worked solution
Marking points
B1 · 1 mark · Mentions that the Kelvin scale starts at absolute zero, linked to zero particle/kinetic energy.
B2 · 1 mark · Explains that the Kelvin scale makes temperature directly proportional in gas law equations, avoiding negative or zero values in calculations.
Worked solution
Scientists use the Kelvin scale because it starts at absolute zero, where particles have no kinetic energy. This means that temperature in Kelvin is directly proportional to the kinetic energy of particles and to the pressure and volume in the gas laws. Using Celsius could give negative or zero values, which do not work correctly in gas law formulas.