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

1. Feb 12, 2013

### 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 ??

2. Feb 12, 2013

### Integral

Staff Emeritus
Re: How much energy do we need to vapourize 1 liter of water???

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.)

3. Feb 12, 2013

### rock.freak667

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

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 + mlv where lv is the latent heat of vaporization of water.

4. Feb 12, 2013

### charlie95

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

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 enery right ??
But how is the equation if want the steam to be 200 degrees???

Last edited: Feb 12, 2013
5. Feb 12, 2013

### charlie95

Re: How much energy do we need to vapourize 1 liter 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???

6. Feb 12, 2013

### Staff: Mentor

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

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.

7. Feb 13, 2013

### SteamKing

Staff Emeritus
Re: How much energy do we need to vapourize 1 liter of water???

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.