Different phases of Formation of steam
Consider formation of steam from ice at -200 C
i)Solid phase- When the heat is added in ice which is at -20 0C, the temperature of ice increases to 00C as shown in figure by process A-B.in this stage solid phase exists.
ii) Solid+ Liquid phase- The point B is called is saturation point when heat is further added this heat cannot increase the temperature but ice is converted into water that means phase transformation takes place, thus in-between region B-C, solid and liquid phase exists.
iii) Liquid phase- From point further heat is added up to 1000 C, in this region no phase change takes place, there is only liquid phase present.
iv) Liquid+ Vapour phase- Point is saturation point; further addition of heat will not increase the temperature but liquid phase change into vapors phase. In this region liquid and vapour is present.
v) Vapour phase- Point is called as saturation point, further adding heat increase the temperature of steam which is called as superheating and in this region only vapour is present.