Here's why:

* Endothermic reactions absorb heat from their surroundings. This is because the products have more energy than the reactants.

* When ice melts, it absorbs energy from its surroundings to break the strong hydrogen bonds holding the water molecules in a rigid, crystalline structure. This energy input is what allows the molecules to move more freely and transition into the liquid state.

In contrast, the reverse process (liquid water freezing into ice) is exothermic. This is because energy is released as the water molecules form those strong hydrogen bonds.