Steam condenses into water when it cools.

蒸汽冷却时凝结为水。

Water vapour condenses to form clouds.

水蒸汽冷凝形成云。

Steam condenses into drops of water.

水蒸气凝成了小水滴。

Steam condenses to water when it touches a cold surface.

水蒸气触及冷的表面即凝结成水。

And, when atmospheric methane condenses, it makes fog.

当大气中的甲烷凝结就形成了雾。