Paper 1, Section II, D
Part II, 2019
(a) Explain, from a macroscopic and microscopic point of view, what is meant by an adiabatic change. A system has access to heat baths at temperatures and , with . Show that the most effective method for repeatedly converting heat to work, using this system, is by combining isothermal and adiabatic changes. Define the efficiency and calculate it in terms of and .
(b) A thermal system (of constant volume) undergoes a phase transition at temperature . The heat capacity of the system is measured to be
where are constants. A theoretical calculation of the entropy for leads to
How can the value of the theoretically-obtained constant be verified using macroscopically measurable quantities?