I did fractional distillation to separate two solvents in my chem lab last week and I was just wondering if someone could check my thinking. So for the first little while after the distillation began, no solvent collected in the receiving flask because the temperature was still making its way up to the more volatile component's boiling point. When the temperature steadied out (at the more volatile component's boiling point) and became more or less constant, the receiving flask started collecting solvent. When the temperature began to increase rapidly, I replaced the receiving flask with an empty flask to collect the second component. Soon the temperature steadied out and became relatively constant, and the flask began to collect the second solvent. I was wondering why we see this steady, constant temperature, followed by a sharp increase, and then another period of constant temperature. Is it because during these periods of constant temperature, the components are in the process of changing from a liquid to a vapour, and temperature remains constant during a phase change? Thanks!