1. Evaporation: This is the process where liquid water changes into water vapor at the surface of the water. It happens when the water molecules gain enough energy (usually from heat) to break free from the liquid and become gas. Think of a puddle drying up on a sunny day.

2. Boiling: This is when water changes to vapor when it reaches its boiling point (100°C or 212°F at standard atmospheric pressure). At this point, water molecules have enough energy to rapidly change state from liquid to gas. Think of water bubbling in a pot on the stove.