Ideal Gas Law:

Yes, we can boil water without external heat !!!

First of all we know about What is Boiling? and How it's boil?
              If we ask a few people how water boils, they answer that when we heat up to 100°C, the water starts to boil. But not only that, but water also can be boiled at room temperature, but that process is a little more extensive.

How does water boil?


               Let assume there is water in a vessel, now that water is in a liquid state because the molecules in the water are compressed, but a few water molecules will try to escape from this compressed water molecular bond, the pressure exerted by water molecules trying to escape and this pressure is called vapour pressure.
               But air pressure above water means that Atmospheric pressure is higher than the Vapour pressure, so water molecules cannot easily escape. The higher this atmospheric pressure, the more equal it is to 1kg per square centimetre of our body; we will specify its measurement as One Bar.
               This is how, when we heat water at 100°C, the water molecules in it begin to move so that the water molecules will start to evaporate. When the water molecules evaporate more, then Vapour pressure also increases, and when the Vapour pressure is higher than Atmospheric pressure, the water starts boiling.

Now we Boil Water without External Heat:

---Water boils without External Heat---

              Let assume we keep the water in a vacuum chamber, and now we suck the air out in that vacuum chamber using a vacuum pump, then the number of molecules decreases in the vacuum chamber. 
              When the Atmospheric pressure is lesser than Vapour pressure, then the water molecules try to escape to increase Atmospheric pressure when it evaporates from the water, then the water will boil at room temperature without external heat that we are given, but it not heated up.
              Now, we know from this that the Atmospheric pressure around the water is low then also the Temperature of the water is low.
               (i.e): Pressure is directly proportional to the Temperature.

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