B.4 Thermodynamics questions for IB Physics

What can cross the boundary of a closed system and of an isolated system?

In a car repair workshop, a car and the platform it rests on have a total mass of 1500 kg. They are raised at a slow, constant speed through a height of 1.8 m by a vertical piston of cross-sectional area $0.090{\text{m}}^2$. Compressed air below the piston is kept at a constant pressure of $2.80\times {10}^5\text{ Pa}$. The atmosphere above the piston is at a pressure of $1.0\times {10}^5\text{ Pa}$.

The outlet of a bicycle pump is blocked and the air inside is compressed. During the compression, 300 J of work is done on the air and 120 J of thermal energy is transferred from the air to the surroundings. What is the change in the internal energy of the air?

A cool box with polystyrene walls contains 2.5 kg of ice at 0 °C. The walls have a total area of $0.80{\text{m}}^2$ and a thickness of 3.0 cm. The thermal conductivity of polystyrene is $0.033{\text{W m}}^{-1}{\text{K}}^{-1}$. The temperature of the outer surface of the walls is 30 °C and the temperature of the inner surface is 0 °C. The specific latent heat of fusion of ice is $3.34\times {10}^5{\text{J kg}}^{-1}$.

A gas in a cylinder is heated slowly. A freely moving piston keeps the pressure of the gas constant at $1.5\times {10}^5\text{ Pa}$ while its volume increases from $2.0{\text{dm}}^3$ to $5.0{\text{dm}}^3$. What is the work done by the gas?

An ocean thermal energy conversion (OTEC) plant uses warm surface sea water at 27 °C as its hot reservoir and cold water pumped from a depth of 1000 m, at 5 °C, as its cold reservoir. The plant produces a useful electrical power output of 1.0 MW. The specific heat capacity of sea water is $4.0{\text{kJ kg}}^{-1}{\text{K}}^{-1}$.