8.41

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Gabriela Carrillo 1B
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Joined: Fri Sep 29, 2017 7:04 am

8.41

Postby Gabriela Carrillo 1B » Sun Jan 21, 2018 6:39 pm

Why can't you set (400g)(4.184 J/Cg)(T-45) equal to (50g)(4.184 J/Cg)(T-0)? Why do we set it equal to the change in state instead?

Ozhen Atoyan 1F
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Joined: Thu Jul 27, 2017 3:01 am
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Re: 8.41

Postby Ozhen Atoyan 1F » Sun Jan 21, 2018 7:01 pm

You have to set it equal to the change, because it asks for the final temperature of the system, so you need to take in account all the types of heat. Therefore, for the ice, you need the heat of the ice melting (q=mCsdeltaT) + heat of the ice at 0 degrees Celsius (q=ndeltaHf). Next, you need the heat of the water, which can be calculated by q=mCsdeltaT. Then you set the total heat of ice and heat of water equal to each other. However, one of them has to be negative because no heat is lost. Thus, q=-q.


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