How is distillation, heating until

How is distillation, heating until almost all the crude oil evaporate at the same time, when I go to pull the Spear of the substance. Each type of substance is steam condensation temperature range throughout the different boiling points. By its low boiling point is going to the area on the condensation of Spears at one another. Section I-of the substance with a higher boiling point, condensation is in the lower position, respectively.