Bubble point and dew point temperature 2

[cherry123]

At bubble point the liquid starts to boil so there is no change of temperature, at the dew point the vapors starts to condense. But why is the bubble point temperature differs from the dew point temperature. When phase changes there is no change of temperature but why is there a difference between the dew point and bubble point temperature.

 

[JLSeagull]

Perhaps you are addressing water or another mono-component fluid. Mixed hydrocarbon streams have an initial boiling point and a final boiling point.