1. The problem statement, all variables and given/known data The temperature of 100 gm of water is to be raised from 24°C to 90°C by adding steam to it .Calculate the mass of the steam required for this purpose . 2. Relevant equations Latent heat of vaporisation of steam = 540 Cal/g 3. The attempt at a solution Let 'm' be the mass of steam added. Heat released by steam as it condenses into water = 540m Heat released by condensed water as it moves from 100°C to 90°C = mx1x10 = 10m Total heat released = 540m+10m= 550m Heat required by 100gm water to raise its temp from 24°C to 90°C = 100x1x66 Equating the two , 550m = 6600 m = 12gm Is it correct ?