Nana: Hey brat, you are suspiciously silent. What’s up?
Nina: Oh, nothing, I am just trying to boil and freeze water at the same time so that it can exist as water, vapour and ice all at once. Easy peasy!
Nana: Stop showing off. What are doing near that burner? I don’t want you blowing up the house.
Nina: It’s a science experiment, Nana. You see, everyone knows the boiling point of water is at 100c and the freezing point at 0c but what many don’t know is that the boiling point and freezing point also depend on pressure.
So, if you adjust the pressure, you can actually make the boiling point and the freezing point, the same.
Nana: You are making this up!
Nina: Of course not! The point at which water can exist as vapour, ice and in liquid form is called the triple point of water which is at 0.01c and at an absolute pressure of 4.58 mm Hg.
The interesting thing about the freezing point is that it doesn’t vary as much with pressure as the boiling point does. Water expands on freezing which means that you can melt ice at 0c, (the normal freezing point) by applying pressure to it. At a higher pressure, the freezing point will be lower, and if you lower the pressure, the freezing point will increase.
Nana: I cannot believe this!
Nina: You better do, because even the omniscient wikipedia declares it so here. More importantly, this is true of all liquids and each liquid can exist in all three states at their own triple point.
Nana: I am getting a headache. Is there a sublimation process for vanishing all the useless geeky facts from your head?
This post is a part of the #NinaAndNana series I co-host with Kanika G.