For any substance, why does the temperature remain constant during the change of state?Why is it needed?
Answers
There are 3 states of any substance. Solid, liquid & gas. The physical state of any substance can be converted to any of those physical states in order.(converting to plasma state is irrelevant in changing physical state). For this procedure either the object is cooled or heated(both are called supplying heat because providing negative heat is called cooling). So let's consider ice at -20 degree C. It will be heated up to O degree C. Now if the temperature of the substance is further increased it will change it's state. So to that sttravtive forces between molecules must be broken because attractive forces in solids are stronger than that of liquids. To break the bonds heat is absorbed by the moleclues. It is not observable that though heat is provided further more, temperature of the substance remains constant because the heat is used to break the bonds & not to increase the temperature of the substance. It is called latent heat of fusion. Same with converting liquids to gaseous state. At that point heat is absorbed to convert liquid molecules to gaseous molecules. It is called latent heat of vaporization.
Because with the increase of temperature, more number of particles get enough kinetic energy to go into the vapour state. Hence temperature remains constant during the change of state.