Answer
A - Solid, B - Liquid, C - Vapor
(a) A is solid phase. As we raise temperature from A, solid ice reaches the melting point and gets converted to liquid water. Upon further raising the temperature, liquid starts to boil and gets converted to steam. Any further increase in temperature just raises the temperature of steam.
(b) C is vapor phase. Starting at C, if we lower temperature at constant pressure, vapor directly gets converted to solid ice.
(c) B is liquid phase. Starting at B, if we lower the pressure at constant temperature, the liquid water starts boiling and forms vapor.
Work Step by Step
A - Solid, B - Liquid, C - Vapor
(a) A is solid phase. As we raise temperature from A, solid ice reaches the melting point and gets converted to liquid water. Upon further raising the temperature, liquid starts to boil and gets converted to steam. Any further increase in temperature just raises the temperature of steam.
(b) C is vapor phase. Starting at C, if we lower temperature at constant pressure, vapor directly gets converted to solid ice.
(c) B is liquid phase. Starting at B, if we lower the pressure at constant temperature, the liquid water starts boiling and forms vapor.
