What example involves a phase change in which heat energy is released by the substance

Spontaneous phase changes that leads to an increase in the stability of a substance would release energy. For example, converting a gas to its liquid state such as cooling water vapor below its boiling point releases energy. Cooling allows water molecules to establish intermolecular hydrogen bonds to produce a liquid while releasing energy. The formation of bonds between water molecules is so exothermic that a steam scald can be significantly more serious to treat than a hot water scald.

because u need two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei to form isotopes.

so since they all have the same shape? i mean maybe because m& m and reeses are both chocolates