Here's why:

* Heat Energy: The sun's rays provide heat energy to the surface of water (or other liquids).

* Increased Molecular Motion: This heat energy causes the water molecules to move faster and vibrate more vigorously.

* Breaking Bonds: As the molecules move faster, they overcome the attractive forces holding them together in liquid form.

* Escape as Vapor: Some of these energetic molecules escape from the liquid surface and enter the air as water vapor.

Let me know if you'd like to learn more about the process of evaporation!