## Molar Heat Capacity for Phase Change of Water

Alyssa Chan 3B
Posts: 16
Joined: Wed Sep 21, 2016 2:57 pm

### Molar Heat Capacity for Phase Change of Water

At constant pressure, why is Cp (s) > Cp (l) > Cp (g) for the phase change of water?

Tyler_Ash_3C
Posts: 25
Joined: Wed Sep 21, 2016 2:57 pm
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### Re: Molar Heat Capacity for Phase Change of Water

It takes more heat to raise 1.00 g of ice by 1.00 degree Celsius than it does to raise the temperature of 1.00 g liquid water by 1.00 degree Celsius. It also takes more heat to raise the temperature of liquid water than to raise the temperature of water vapor. The equation q=cm(change in temperature), relates heat to specific heat. However, this equation is not associated with a phase change. Phase changes are represented by the flat portions of a heating curve, and the heat added or removed does not cause a change in temperature, so this equation is not applicable to phase change situations. In other words, the specific heat can be different for a substance in different states matter. The actual reasoning behind this had to do with the strength of intermolecular and intramolecular forces in different states of matter, but we are not expected to fully understand this.