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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: kelluminati on June 08, 2020, 08:40:05 PM

Title: Freezing and Melting Points
Post by: kelluminati on June 08, 2020, 08:40:05 PM

Hi there!
I understand how and why the freezing point and melting point of a substance can be the same. However, I'm stuck on understanding if...
1. SOME or ALL particles lose enough energy to go from the liquid state to solid?
2. SOME or ALL particles gain enough energy to go from the solid state to liquid?
Thanks in advance!

Title: Re: Freezing and Melting Points
Post by: Borek on June 09, 2020, 03:20:12 AM

Hint: imagine having a mixture of ice and water. If the mixture is stable (nothing melts or freezes) what is its temperature? What happens when you add a bit of heat? Will the temperature change? What happens when you add a lot of heat?

Title: Re: Freezing and Melting Points
Post by: Enthalpy on June 10, 2020, 04:58:14 AM

The freezing or melting point is measured when both the solid and the liquid are present. Necessarily, a part of the matter has enough energy to be liquid, the other part has not.

The proportion of liquid versus solid depends on how much heat is in the matter, but the melting temperature is constant. So the fraction of the matter with enough energy to be liquid does not result from a statistical distribution computed from the temperature.