Evaporation requires the removal of heat?

  • #1

Main Question or Discussion Point

I'm missing out on something here.

I'm studying how the cooling tower works and it says that the "water evaporates and removes heat". The thing is, shouldn't the heat be added to the water for it to evaporate and thus increasing the heat? If we want water to evaporate, we boil it with fire, which is once again heat addition.

Care to clarify this for me?
 

Answers and Replies

  • #2
87
4
Water needs heat to evaporate, but the heat does not increase temperature of water: the heat is used to free the water molecules. It is called the latent heat. Water gets this latent heat from the sorrounding material, so the sorroundings get cooler.
 
  • #3
1,254
105
We boil it so that the water is hotter than the air and then it evaporates quickly. If we don't boil it then it will be room temperature, and it will still evaporate. This is because water has many molecules in it and some are more energetic than others. The "hotter" (more energetic) molecules and bits of water have enough momentum to escape the liquid and go into the atmosphere. This leaves the liquid cooler because the hot molecules have escaped. This should jive with your personal experience. If we boil water it cools down as it evaporates, the hot water is leaving. If you sweat you cool down because the hot water molecules on your body leave and what is left are colder molecules.
 
  • #4
Thanks to both of you but the answer I was looking for was answered by mpv_plate. Appreciated!
 

Related Threads on Evaporation requires the removal of heat?

  • Last Post
Replies
4
Views
1K
Replies
0
Views
6K
  • Last Post
Replies
2
Views
1K
Replies
2
Views
20K
  • Last Post
Replies
2
Views
5K
Replies
10
Views
4K
  • Last Post
Replies
2
Views
709
Replies
3
Views
911
Replies
2
Views
691
Top