phase changes

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Malaya Du 2G
Posts: 8
Joined: Fri Sep 25, 2015 3:00 am

phase changes

Postby Malaya Du 2G » Sun Jan 17, 2016 10:32 pm

I don't understand why we have to calculate the heat for phase changes before we can calculate the rest of the problem. For example why is there a heat value attached to the change from ice to water instead of just going straight to the heat changes for the rest of the reaction?

Annie Qing 2F
Posts: 28
Joined: Fri Sep 25, 2015 3:00 am

Re: phase changes

Postby Annie Qing 2F » Sun Jan 17, 2016 10:51 pm

I'm not sure if this is exactly what you mean but
To change from ice to water (and then heat up the water), you have to calculate the heat required for both parts: changing the phase and then heating up the water.
So it's easy to do these in order. First we figure out how much energy we need to put into the ice to change it to water (which does not change the temperature at all) and then how much energy we need to put into the water to get it to how hot we want it.

Hope this helped!


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