What do we mean when we refer to the term 'absolute zero'?

Absolute zero is defined as the theoretical point at which all molecular motion ideally ceases. This occurs at 0 Kelvin, which is equivalent to -273.15 degrees Celsius. At this temperature, the kinetic energy of particles reaches its minimum, meaning that the particles would be in their lowest energy state.

This concept is fundamental in the study of thermodynamics and statistical mechanics, as it establishes a baseline for the behavior of substances in relation to temperature. While it may not be physically achievable in practice, understanding absolute zero helps explain phenomena such as thermal energy and the behavior of gases at very low temperatures.

The other options describe different aspects related to temperature and states of matter but do not accurately capture the essence of absolute zero. For instance, the temperature where gases become liquids pertains to the concept of condensation, not absolute zero. Similarly, while the lowest temperature ever recorded may be extremely close to absolute zero, it does not represent the theoretical concept of absolute zero itself. Lastly, stating that all substances are solid at absolute zero is misleading, as some materials may form other states or structures even at such low temperatures.