Evaporation

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Water molecules are sticky, so they tend to stick together to form a liquid. If the water is given some energy, by being heated or blown by the wind, some of the molecules near the surface can escape into the air. They form a gas (also known as water vapor).
If the free molecules meet ions in the air, they may condense (stick to the ion and to each other) to form droplets of liquid water floating in the air. These droplets stop light, and so can be seen as white clouds.