Absolute zero

Definition

Absolute zero is the lowest possible temperature where all molecular motion ceases. It is 0 Kelvin, or -273.15 degrees Celsius.

5 Must Know Facts For Your Next Test

1. Absolute zero is the theoretical temperature at which a system's entropy would reach its minimum value.
2. At absolute zero, the thermal motion of particles in a substance would be minimal, but quantum mechanical effects still persist.
3. It is not possible to reach absolute zero exactly due to the Third Law of Thermodynamics.
4. Absolute zero serves as a reference point on the Kelvin temperature scale, which is an absolute thermodynamic scale.
5. $0$ K equals $-273.15^{\circ}$C and $-459.67^{\circ}$F.

Review Questions

• What happens to molecular motion at absolute zero?
• Why can't we reach absolute zero according to the Third Law of Thermodynamics?
• Convert $0$ K to Celsius and Fahrenheit.

Related terms

Kelvin:

A unit of measure for temperature based on an absolute scale where $0$ K is absolute zero.

Third Law of Thermodynamics:

States that as the temperature approaches absolute zero, the entropy of a system approaches a constant minimum.

Entropy:

A measure of disorder or randomness in a system; it tends to decrease as temperature lowers towards absolute zero.