Does evaporation raise or lower temperature of water?

Answer 1

The kinetic energy of atoms (and molecules) in a system (in our case a liquid) follows a normal distribution - this is the bell shaped curve that you maybe familiar with in generating grades. It represents the number of atoms at a certain energy level: the maximum population being in the center.

This distribution is maintained as atoms are constantly trading off energy through collisions. All collisions result in the exact same total energy but the individual energies of the involved particles can vary. One atom can have its velocity elevated while the velocity of the other is depressed.

If then a certain atom has its velocity (energy) elevated into the extreme high end of the distribution tail then it has enough energy to evaporate and does so.

Now the total energy of the liquid/gas system remains the same however the energy of the isolated liquid system has gone down, energy has been removed from it. The liquid then willreadjust the distribution of the energies (velocities) of its individual atoms to reacquire the normal distribution. (NOTE: in statistical thermodynamics we say 'will' not 'must' as the quantum mechanics are allowed to. We can only say what the system as a whole will do not what individual atoms do.)

Redistributing energies to fit the normal distribution then, when there has been a net energy loss, requires the system to depress the value of the population of its maximum value - in other words the whole of the bell-curve shifts to the left - towards lower temperatures.

Answer 2

No. Increasing the temperature of a liquid increases its rate of evaporation. As the temperature increases the particles become more energetic and are able to leave the solution to form vapor more easily.

Answer 3

Quick answer: At the surface of the liquid, the most energetic (hottest) liquid molecules are the ones that make the phase change to a gas.

So simply - only the hottest (most energetic) molecules leave the liquid, which then leaves behind the colder molecules (less energetic). In this way, the *average* temperature of the liquid cools.

Answer 4

It is the hot molecules that escape first.

Remember that Temperature is the average velocity of the molecules. Some are fast, and some are slower.

The faster ones are able to break free, and the averagetemperature thus drops.

(read that carefully)

And this will continue till all the molecules with sufficient energy have broken free.

Answer 5

Evaporation lowers the temperature of water. When the more energetic water molecules with higher kinetic energy escape from the liquid surface into the air, only the less energetic water molecules with lower kinetic energy are left in the liquid. The liquid will cool as a result of the loss of energy through evaporation.