Question

Please calculate the amount of energy it will take to change 10.0 Grams of Water from -3 C to changing it all to vapor at sea level. Show all your work for credit.

heat of fusion of water = 334 J/g

heat of vaporization of water = 2257 J/g

specific heat of ice = 2.09 J/g·°C

specific heat of water = 4.18 J/g·°C

Answer 1

It looks like we have to use the energy formula twice, one from ice to liquid, and liquid to vaporization..what do you think?

Answer 2

oh...yeah! if I knew how to do that...my teacher isnt very good at explaining..

Answer 3

Actually, not 100% sure. There doesn't seem to be a change in temperature in your given info so I'm not sure whether we need to figure out a tfinal or what not.

@aaronq @matt101

Answer 4

Yes as @dtan5457 says, we need to do this in several steps. You'll need to calculate the amount of heat required for each of the following:

1. Warming the ice from -3 C to 0 C (using specific heat of ice)
2. Converting the ice to water (using heat of fusion of water)
3. Warming the water from 0 C to 100 C (using specific heat of water)
4. Converting the water to vapour (using the heat of vaporization of water)

Add all 4 numbers together to get the TOTAL heat required!

Answer 5

Small side note - the fact that we're at sea level is only important because that way we know the freezing and boiling points of water are at 0 C and 100 C respectively.

Answer 6

Quick question @matt101
When we convert the ice to water (heat of fusion), we just multiply 334 j/g by 10, right?

Answer 7

So 2 of the steps, we use the energy formula and the other 2 we multiply accordingly to the fusion/vaporization .?

Answer 8

WOW...that's all i have to say haha...this is tough

Answer 9

Yup! The goal is to get energy, so just by looking at units you can tell that multiplying J/g by g leaves you with J, just as multiplying J/g C (specific heat) by g and C leaves you with J.

Heats of fusion/vaporization/etc are typically given in J/g or something similar, without temperature, because these values are referring to a PHASE change during which the temperature remains constant. That means the only thing that affects the amount of heat required for the phase change to occur is how much of the stuff you actually have.

Answer 10

now im just confused :(

Answer 11

Oh, well this does make a lot more sense now.

Answer 12

maybe cause you guys are smart :/

Answer 13

@sophadof
Look back at matt's steps, he lays them out pretty clearly and do them one by one, shouldn't be too bad.

Answer 14

This question is more of keeping track that you got every step done, while the steps only take a few seconds to do , lol.

Answer 15

haha

Answer 16

I will try my best ? :/

Answer 17

go for it

Answer 18

I literally..do not understand

Answer 19

There are two things you need to know

in matt's steps, when you need the specific heat of something

you always use the energy formula which

energy=mass x specific heat x change in temperature

when you just use fusion/vaporization, you just multiply the given amount by the mass, (in this case 10 grams)

Answer 20

thank you!!!!!!!!!!!!!!!(:

Answer 21

can I let you know when im done? @dtan5457

Answer 22

Just post your answer here and someone will have a look!