A physics teacher puts her cup of coffee on a table in a classroom. The coffee has a mass of 250 g and a temperature of 85 °C. The classroom is at a temperature of 20 °C. The teacher forgets her coffee because a student asks her an interesting question about thermodynamics. The coffee starts to cool down. Calculate
(1) the thermal energy lost by the coffee as it cooled to a temperature of 30 °C (the specific heat capacity of the coffee can be taken to be 4.2 kJ kg−1∘C ; you may ignore the cup itself).
(2) the average temperature of the coffee during its cooling.
(3) the change in entropy of the coffee as a result of cooling.
(4) the change in entropy of the classroom (assume that the temperature of the classroom does not change).
(5) the net change in entropy of the universe as a result of the coffee cooling.