Here's why:
* Solid state: In a solid, particles are tightly packed and have strong intermolecular forces holding them together.
* Liquid state: In a liquid, particles have more freedom to move around, and the intermolecular forces are weaker.
* Energy input: To break the strong bonds in a solid and allow the particles to move more freely, energy must be added to the system. This energy is absorbed as heat.
Think of it like this: Imagine you have a block of ice (solid). You need to add heat (energy) to melt it into liquid water.
