How much energy do we need to vapourize 1 liter of water?

[charlie95]

How much energy do we need to vapourize 1 liter of water?

How much energy do we need to vapourize 1 liter of water?

I know that to heat up 1liter of water by 1 degree, you need 1kcal(or 4,2kj/kgK).
So let us say that th water is 0 degree at start temperature, and that the boiling temperature is 100 degree.
So is the answear then: 4,2*100=420KJ ??

 

[Integral]

That gets the water to 100C but not vaporized. For that you need to add in waters heat of vaporization. (you can do a web search to find that number.)

 

[rock.freak667]

If you are starting as liquid water at 0 degrees C, then the total energy needed would be the energy to increase the temperature from 0 deg C to 100 deg C + the energy required to change the phase of the water from liquid to gas (latent heat)

Q= mcΔT + ml_v where l_v is the latent heat of vaporization of water.

 

[charlie95]

Thanks...
Q= mcΔT + mlv is just for steam at 100 degrees ? So if I want the steam to increase in temperature I need to add more energy right ??
But how is the equation if want the steam to be 200 degrees?

 

[charlie95]

If you are starting as liquid water at 0 degrees C, then the total energy needed would be the energy to increase the temperature from 0 deg C to 100 deg C + the energy required to change the phase of the water from liquid to gas (latent heat)

Q= mcΔT + ml_v where l_v is the latent heat of vaporization of water.

To get 1kg of water at 0 degrees to steam at 100degrees you need:
(1Kg*4,2KJ/KgK*100K)+(1Kg*2260KJ/Kg)=2680KJ, right?

 

[Chestermiller]

That's only if the water is vaporized at 100C. Of course, it can also be vaporized at all other temperature, up to the critical temperature, with different amounts of heat required.

 

[SteamKing]

To find out how much heat is required to raise the temperature of 100C steam to 200C, you'll have to find out the specific heat of steam.

A more practical approach is to use a steam table.