The Naked Scientists

The Naked Scientists Forum

Author Topic: How much steam from 500 calories of heat added to 2 litres of water?  (Read 3069 times)


  • Guest
xam asked the Naked Scientists:
If five hundred kcal of heat is added to 2kg of water at 80°C, how much steam is produced?

What do you think?
« Last Edit: 15/10/2011 19:01:02 by _system »


Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
Is this a math and science homework problem?

Typically I start by converting everything to grams and calories.
1000 calories = 1 kCal.
1000 grams = 1 kg.

1 calorie will raise 1 gram of water 1°C.
However, it takes 79.72 calories to vaporize one gram of water at 100°C.

So, what you basically do is calculate the number of calories to raise the water from 80°C up to 100°C

Subtract that from your total amount of energy, and that gives you the energy left to vaporize the water.  If it is negative, then you would not get any steam, and you could calculate the final temperature.

Assuming you still have some energy left over, you simply divide the the remaining energy at 100°C by 79.72 calories/gram to get the number of grams of steam vaporized.

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
I'll give you a hint - less than half of it.

The Naked Scientists Forum


SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums