The liquid boils and freezes at the same time

Cyclohexane is poured into a flask in a vacuum state. When the pressure in the flask decreases, the cyclohexane on the surface begins to freeze and the liquid beneath the boiling, creating a continuous liquid-solid state transition.

Close up of boiling liquid and freeze at the same time

Professor Martyn Poliakoff at the University of Nottingham, UK, explains: "When the vacuum pump operates, the pressure in the flask decreases until it reaches the pressure level at the boiling point of cyclohexane at room temperature (temperature Boiling of liquids depends on pressure, usually, when the pressure drops, the boiling temperature decreases).

The liquid starts to boil but the liquid evaporation needs energy, so the temperature near the surface decreases. Because cyclohexane has a high melting point, the liquid freezes. Then, because there is a layer of solid on the surface, the boiling process stops. Next, or because the heat from the liquid layer below, or because the solid layer is broken, the liquid continues to boil. "