Triple point of a substance: What is it?

Hi all !! this is Suven Jagtiani writing this blog. I am a student studying in 9th grade.I was in my chemistry class and learnt this brilliant phenomenon of triple point. So I came up with this blog to explain the interesting concept of triple point of chemicals.

WHAT IS TRIPLE POINT?

Triple point is basically the temperature and the pressure at which a substance can exist in all the three states of matter.[What??]
You would be knowing that temperature can affect the state of matter of a substance.Even pressure has this ability to change the state of matter of a substance. So, triple point does not only depend upon the temperature but also on the pressure.

WHY DOES THE TRIPLE POINT EXIST?[I will take the example of water]

The triple point is there because that is where the three phases (solid, liquid and vapour) of a substance can coexist in thermal equilibrium with one another. At all other temperatures[with normal pressure] only two (or one) phases can co-exist together in thermal equilibrium.

[You might say that you can have ice in a beaker of water with the top of the beaker covered and eventually the ice and the water and the water vapour will all reach the same temperature. So here you have all three phases of water in thermal equilibrium with one another and so it must be the triple point. That is not so because there is also air present which applies pressure and upsets the equilibrium .]

Water exists in three distinct phases at something called the triple point. Zero degrees celsius is defined by the triple point of water which is 273.16K at 611.2 Pa. 
At this temperature water is in the process of changing from a solid state into the liquid phase or visa versa. Molecules in the liquid phase can loose a bit of energy and solidify whilst solid water (ice) can gain some energy and melt. This can be seen in melting ice where the solid ice exists for some time while the exposed surface melts. 
Molecules in a liquid don't all have the same energy. The energies of the molecules can vary from a finite minimum, which would mark the transition back to a solid phases, up to an infinite energy (although the probability of this occuring is infinitely small). The average energy of the molecules gives us the temperature of the liquid. Statistical thermodynamics can map out the energy distribution of the water molecules. At a certain energy molecules will have enough energy to evaporate, even if the water temperature is 0 degrees C. 

THIS IS A PHASE DIAGRAM

            THANK YOU FOR READING!!!