how the water present in ponds got emptied in summer, without getting the temp of 100 degre centigrade. plaese explain the phenomenon.

Capuchin

Not all the molecules in a volume have the same energy, temperature is a measure of the average energy of particles. Some particles will have energy greater than the energy needed to escape the surface of the water and evaporate, because the particle's energies are distributed about the average.

In summer, more energy is given to the water molecules by the sun, so more molecules are able to escape in this way.



Here is a picture of molecules in a room, they dont all have the same energy, some are fast and some are slow. The temperature of the gas in this box is a measure of the average energy. If we imagined this is a liquid, and that the top of the box is the surface of the liquid. If a molecule hit the surface with a high enough energy, it would be able to escape and evaporate, even if the temperature is below 100.

The red molecules are just so that it's easier to follow them with your eye.

Hope this helps!

Capuchin

...how could i make it clearer? What do you disagree with in my answer?

Capuchin

Okay let me see if this helps:



This shows the distribution of energies of the particles at a certain temperature. The "activation energy" (in this case) is the energy needed for a particle to escape the surface of the water. (it's not called the activation energy, but the same principle applies to chemical reactions which is where i swiped this picture from)

The peak of the curve (the mode) is close to (slightly before) the mean, this is the energy that a particle of the average energy has. This is indicative of the temperature, you can see that it is below the activation energy.

You can also see that some particles are above the "activation energy". This distribution shows that at a temperature below the evaporation point, some particles still have enough energy to escape.

I hope that helped a little more.