What statement is true regarding Avogadro's number?

Avogadro's number, which is approximately (6.022 \times 10^{23}), defines the number of constituent particles, typically atoms or molecules, contained in one mole of a substance. This fundamental constant allows chemists to relate macroscopic amounts of substances to the number of particles they contain, facilitating calculations in stoichiometry and other chemical processes.

In this context, the statement regarding the definition of a mole of any substance aligns perfectly with the role of Avogadro's number. It applies regardless of whether the substance is a solid, liquid, or gas, confirming its versatility across different chemical contexts.

The other statements do not accurately describe Avogadro's number. It is applicable to all types of matter, not just gases, and does not measure temperature or represent energy in a mole. Thus, defining a mole of any substance correctly highlights the significance and universality of Avogadro's number in chemistry.