Chapter 8 #87

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Frances Relampagos 1J
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Joined: Fri Sep 25, 2015 3:00 am

Chapter 8 #87

Postby Frances Relampagos 1J » Sun Jan 31, 2016 9:31 pm

I'm really confused about calculating phase changes. On number 87, it's asking for how much heat is required to convert a block of ice into water vapor. In the solutions manual, it lists the steps of each different changes but I'm confused where they're getting the numbers such as temperature and which heat capacity to use. Can someone explain to me the overall procedure like how each step is done and why they used that certain heat capacity. Thanks!

Daniel Fu 2K
Posts: 10
Joined: Fri Sep 25, 2015 3:00 am

Re: Chapter 8 #87

Postby Daniel Fu 2K » Sun Jan 31, 2016 9:42 pm

So to explain how the get the values, in order to melt ice at -5.042 C to 150.35 C, you need to five equations to calculate this.
1. First you need to calculate the temperature of ice from -5.042 C to 0.0C using Ice's specific heat capacity, which is different from water.
2. Then you need to calculate Ice's phase change into water which does not change temperature. Look up the value for that.
3. Following that, you need to calculate the temperature change of water from 0.0 C to 100.0 C using liquid water's specific heat capacity.
4. Then you need to calculate water's phase change into gas which also does not change the temperature. Look up the specific value needed to undergo the phase change. This process is similar to step 2.
5. Last of all, calculate the temperature change of water vapor from 100.0 C to 150.35 C, and like the first and third step, use the specific heat of water vapor in that calculation.
Hope that helps.

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