heat of a phase change

josephyim1L
Posts: 61
Joined: Fri Sep 28, 2018 12:15 am

heat of a phase change

what is the formula for finding the heat of a phase change?

305113590
Posts: 66
Joined: Fri Sep 28, 2018 12:28 am

Re: heat of a phase change

There are three places where temperature increases (solids, liquids, and gases). These places where temperature increases utilizes mC∆T where C is the specific heat capacity for water at a certain phase.
Then, there are places where temperature does not change and they are phase changes (melting and vaporization). This is where we utilize n∆H of fusion or vaporization.

Matthew Choi 2H
Posts: 59
Joined: Fri Sep 28, 2018 12:18 am

Re: heat of a phase change

For phase changes, keep in mind that the temperature of the substance in question does not change. You can see that if you look at a heating or cooling curve. Therefore, you can't use q=(m)(C)(delta T) because you would end up with 0 due to the net change in temperature being 0. Instead, you have to use the delta H of fusion or vaporization and calculate the amount of energy using the amount of substance you have.

Megan_Ervin_1F
Posts: 78
Joined: Fri Sep 28, 2018 12:18 am

Re: heat of a phase change

Phase changes occur when the temperature is constant on the flat lines of the heating curve and you use: mass X enthalpy

Xingzheng Sun 2K
Posts: 62
Joined: Fri Sep 28, 2018 12:29 am

Re: heat of a phase change

During the phase change, the heat is called latent heat. The formula is q=mL (L is latent heat capacity).

Jack DeLeon 1B
Posts: 30
Joined: Fri Sep 28, 2018 12:20 am

Re: heat of a phase change

Depending on what unit the question is asking for, you can use moles x delta H or mass x delta H.

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