Why does fresh water evaporate faster then salt-water?

Saltwater evaporation facts?

• Saltwater evaporation ideas for facts and keywords to include on poster? My son is doing a project on tap water and salt water evaporation. Topic is which of the two will evaporate faster. My question is on his poster for the presentation what are some important key words and facts that would make this presentation a bit more interesting? The experiment was came easy for him (6th grade). I want him to explore the topic and make some good points in his presentation. I've done some research but there is much to cover. I'm just looking for some ideas.His poster is a little blah he said and he's read all materials provided. He asked me for some ideas anything cool to improve it.

• Answer:

  Vaporization is the main topic. Molecules of water will gain enough thermal energy to break free from the liquid water surface and dissolve into the air above it. Words to look up: 1. Vaporization 2. Heat of vaporization 3. Knudsen layer <-- This is an interesting layer that is only a few molecules in depth (a distance so short you measure it in nanometers or angstroms) on the boundary of liquid water and the air where individual water molecules can gain enough kinetic energy to change from liquid to gaseous phase. 4. Kinetic theory of gasses. It's a little heavy for sixth grade, but parts are fairly easily described. The idea of energy from the sun being absorbed as heat by the water causing evaporation might be a useful tool for describing evaporation. Fresh water and salt water both have this layer.