Q4. A small cup of tea at 60 °C is placed in a large room at 25 °C. The room holds far more internal energy than the tea. In which direction does heat flow?
From the tea to the room, because the tea is at the higher temperature. The amount of energy each holds does not decide the direction.
Q5. A 60 W lamp runs for one hour and all the electrical energy ends up as heating. How much energy is this, in joules and, using 1 cal = 4.186 J, in kilocalories?
60 × 3600 = 2.16 × 10 J, which is 2.16 × 10/4186, about 51.6 kcal.
Q6. Body A is in thermal equilibrium with body C, and body B is also in thermal equilibrium with C. If A and B are placed in contact, will heat flow between them?
There is no net heat transfer. A and C are at the same temperature, and so are B and C, so A and B are at the same temperature as each other. (This is the zeroth law of thermodynamics, met in the next chapter.)