How does steam condense?

Answer 1

Water becomes steam when it is given enough energy to overcome its molecular bonds with its neighbouring molecules. This is called the latent energy, think of it like a group of people holding hands, they are restricted in their movement by the group and all have to stay roughly together. Now the latent energy is the energy required for someone to come along and break up all 'hand holding' so that the people are allowed to move around independently of the group. This allows the single people to move wherever they like and they generally spread out 'diffuse' into the allowed space. This is what happens when you give enough energy to water, the molecules spread out and become steam. Now for steam to condense it is the exact opposite, the latent energy, needs to be removed from the group of people, this energy is generally removed by exposure to a cold enviroment, if you think of it like the group of people again, imagine they where outside and it suddenly got very cold, they would all begin to huddle up again and become the same group of people that they where when they started. This is how and why steam condenses when it meets a cold surface, ie a mirror or your windscreen.

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