Supercooling and Superheating

Under equilibrium conditions, a liquid will freeze if cooled below its freezing point, or boil if heated above its melting point.
But if the system is not in equilibrium, it can remain in the liquid phase as it is supercooled below their freezing point, or superheated above its boiling point.

[@sevenup8048]

Wow. U make it really clear to understand the concept.

[@PhysicalChemistry]

I'm happy to hear it. That's my goal

[@cakefactoryy]

WOW Super easy to understand!

[@adrianmendez4545]

Thank you, you are so good explaining.

[@PhysicalChemistry]

You're welcome, I'm happy to hear that

[@차수민-b6o]

Does this mean that water can exist in a liquid state even at temperatures very close to absolute zero?

[@PhysicalChemistry]

No, there is a lower limit (sometimes called the spinodal temperature) below which water (or any substance) is not even temporarily stable as a liquid

[@JEE-zm3sh]

2:39 can u please explain why 'slight perturbation'? how to realise it with respect to the graph?

[@koussaybelhaj1280]

Doesn't the temperature stop increasing when the boiling point is reached, how can there be superheating then?

[@kothandaramanramanujamiitm9493]

great explanations

[@mahmoudelgharabawy1258]

how can these stones or boiling chips prevent this phenomenon of water explosion?

[@PhysicalChemistry]

In a smooth glass flask, there are not many sites that can serve as nucleation sites where gas bubbles can form. So it is easy to superheat the liquid.
The boiling chips have lots of little irregularities on their surface. These serve as good nucleation sites for the gas bubbles. So the liquid can boil more readily, and doesn't superheat.
You may notice that I have sort of dodged the question, and you may ask: Why do gas bubbles form more easily in one place than another? Or, phrasing it as a PChem question: why is the free energy cost for forming a gas bubble smaller on the surface of a boiling chip than it is on the glass, or in the middle of the liquid? It turns out that PChem can answer that question, too, in a fascinating way. I haven't recorded a video on that topic, but I hope to do so in the future as it is a fascinating topic. (Spoiler alert: see the Kelvin equation)

[@xaiver3612]

@@PhysicalChemistrydid you make a video about it yet???

[@PhysicalChemistry]

@@xaiver3612 no