* Endothermic reactions absorb heat from the surroundings. This means the products have a higher enthalpy (energy content) than the reactants.

* Stability is related to energy content. Molecules with lower energy content are generally more stable. Think of it like a ball rolling down a hill. It's more stable at the bottom of the hill because it has less potential energy.

Therefore, since endothermic products have higher energy than the reactants, they are less stable.

Example:

The melting of ice is an endothermic process:

H₂O (s) + heat → H₂O (l)

Liquid water (H₂O(l)) is less stable than solid ice (H₂O(s)) because it requires energy to break the strong bonds in the ice structure and form the less organized liquid structure.