In a physics laboratory, liquid nitrogen is kept in an open vessel at its boiling point of 77 K. Due to heat transfer from the room, the liquid nitrogen boils slowly, converting into nitrogen gas at a constant temperature of 77 K.
Which of the following correctly describes the changes in the average kinetic energy and the total potential energy of the nitrogen molecules during this vaporisation process?
Both the average kinetic energy and the potential energy of the molecules increase.
The average kinetic energy of the molecules increases, while their potential energy remains constant.
The average kinetic energy of the molecules remains constant, while their potential energy decreases.
The average kinetic energy of the molecules remains constant, while their potential energy increases.
56 exam-style questions on OCR A A Level Physics Thermal physics, covering Temperature, Solid, liquid and gas, Thermal properties of materials, and Ideal gases. Each one has a worked solution and a mark scheme showing where the marks go.