Thermodynamics：練習題

In the first law of thermodynamics, the change in internal energy \(\Delta U\) is given by the equation \(\Delta U = q + W\). What do the symbols \(q\) and \(W\) represent in this convention?

The air in a bicycle pump is compressed so rapidly that no heat is transferred to or from the surroundings. During this compression, the pump becomes warm.
Which statement correctly explains this observation using the first law of thermodynamics?

An ideal gas is heated at constant volume. If \(400 \text{ J}\) of heat energy is transferred to the gas, what is the change in the internal energy of the gas and the work done on the gas?

Which statement best describes the internal energy of a system?

For an ideal gas, which component of the internal energy is assumed to be zero?

Define internal energy of a system in terms of its constituent molecules.

A gas absorbs thermal energy of value q and performs work of value W on its surroundings. Using the first law of thermodynamics, state the expression for the increase in internal energy \( \Delta U \) of the gas.

A gas expands from \( 2.0 \times 10^{-4}\text{ m}^3 \) to \( 6.0 \times 10^{-4}\text{ m}^3 \) at a constant pressure of \( 3.0 \times 10^5\text{ Pa} \). If the internal energy increases by \( 180\text{ J} \), calculate the thermal energy \( q \) transferred to the gas.

A sample of an ideal gas is contained in a cylinder. The gas expands from an initial volume of \(2.5 \times 10^{-4} \text{ m}^3\) to a final volume of \(6.5 \times 10^{-4} \text{ m}^3\) at a constant atmospheric pressure of \(1.0 \times 10^5 \text{ Pa}\).

Part (a)
Calculate the work done by the gas during this expansion.

Part (b)
State the value of the work done on the gas used in the first law of thermodynamics equation.

A gas is held in a vertical cylinder by a piston of mass \(m\), as shown in the diagram. When the gas is heated, the piston moves upwards at a constant speed.

Part (a)
Explain why the work done on the gas during this expansion is negative.

Part (b)
During the expansion, the gas absorbs 800 J of thermal energy and the internal energy increases by 550 J. Calculate the work done by the gas against the piston and the atmosphere.