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The answer:

Final form : Liquid+vapour

Final temperature: 100°C

I have no idea how to do this!

Plz help!

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- Thread starter Lennonlim123
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- #1

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The answer:

Final form : Liquid+vapour

Final temperature: 100°C

I have no idea how to do this!

Plz help!

- #2

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Start by understanding the physical situation. Even without looking at the answer, do you see that you are heating water, maybe until some or all of it evaporates?

Do you know how to figure out how much water heats from adding a given amount of energy?

- #3

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But how to apply it here?

Wait, I forgot.

The latent heat of vapourise is 2x10^6

The heat capacity of water is 4200

Heat capacity of vapour is 2100

- #4

Andrew Mason

Science Advisor

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Generally, you have to follow the rules and tell us what you have tried first. I will assume you don't know where to start. To get a start, answer these questions:

How much energy does the heater add to the water in 25 min.? (hint: you are given the amount of energy is added to the water each second).

How much energy does it take to raise a kg of water one degree C.? How much energy does it take to raise .2kg one degree C?

How much energy does it take to raise .2 kg of water to the boiling point?

How much energy does it take to vaporize one kg of water at that boiling point? How much for .2 kg of water?

(Note: assume the tank is at atmospheric pressure).

AM

- #5

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I usually see that written as Q=mc∆TI only know Q=mctheta

It says that the the amount of heat (Q) added to a body equals the product of the mass (m), the heat capacity (c) and the change of temperature (∆T)

That lets you see where Andrew Mason's first leading question comes in:

How much energy does the heater add to the water in 25 min.? (hint: you are given the amount of energy is added to the water each second).

The answer to that will give you the value to substitute for Q (assuming all the heat goes into the water and stays there until the water boils).

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