Thermodynamics

State what is meant by the internal energy of a system.

Explain why the internal energy of an ideal gas is directly proportional to the thermodynamic temperature of the gas.

A sample of an ideal gas at thermodynamic temperature $T$ has internal energy $U$.

The gas is compressed so that its temperature increases to $3T$.
During this compression, work $W$ is done on the gas.

The gas is then cooled at constant volume so that its temperature decreases to $2T$.

Complete Table 4.1 to show, in terms of some or all of $W$, $T$ and $U$, the work done on the gas, the thermal energy supplied to the gas and the increase in internal energy of the gas for each of the two processes.

Table 4.1

State what is meant by the internal energy of a system.

Explain why the internal energy of an ideal gas is directly proportional to the thermodynamic temperature of the gas.

A sample of an ideal gas at thermodynamic temperature $T$ has internal energy $U$.

The gas is compressed so that its temperature increases to $3T$.
During this compression, work $W$ is done on the gas.

The gas is then cooled at constant volume so that its temperature decreases to $2T$.

Complete Table 4.1 to show, in terms of some or all of $W$, $T$ and $U$, the work done on the gas, the thermal energy supplied to the gas and the increase in internal energy of the gas for each of the two processes.

Table 4.1

State two ways in which the first law of thermodynamics describes that the internal energy of a system may be changed.

1 ______

2 ______

Use the first law of thermodynamics to explain why a bicycle pump gets hot when it is used to pump up a tyre quickly.

With reference to molecular energies, explain why the temperature of water remains at $100\ ^{\circ}\text{C}$ when it vaporises in a kettle, even though it is being heated.

State the first law of thermodynamics.

Use Fig. 4.1 and Fig. 4.2 to determine the general expression for the internal energy $U$ of the gas when it has pressure $p$ and volume $V$.

$U$ = ______

An ideal gas at thermodynamic temperature $T$ contains $N$ molecules.

Use your answer in (b)(i) and the equation of state for an ideal gas to deduce an expression for $U$ in terms of $N$ and $T$. Identify any other symbols you use.

$U$ = ______

change AB

$W$ = ______

change CD.

$W$ = ______

Use your answers in (c) and the first law of thermodynamics to determine an expression, in terms of $X$ and $Y$, for the net thermal energy $Q$ supplied to the gas during one full cycle ABCDA. Explain your reasoning.

$Q$ = ______

State two ways in which the first law of thermodynamics describes that the internal energy of a system may be changed.

1 ______

2 ______

Use the first law of thermodynamics to explain why a bicycle pump gets hot when it is used to pump up a tyre quickly.

With reference to molecular energies, explain why the temperature of water remains at $100\ ^{\circ}\text{C}$ when it vaporises in a kettle, even though it is being heated.

State what is meant by the internal energy of a system.

a gas is heated at constant volume so that its temperature increases

a wire is stretched within its elastic limit at constant temperature.

State the first law of thermodynamics. Identify the meaning of any symbols that you use.

Complete Table 3.1 for the changes A to B and B to C by placing two ticks (✓) in each row.

Table 3.1

Use the first law of thermodynamics to describe and explain the energy transfers associated with one complete cycle ABCDA.

State what is meant by the internal energy of a system.

of a spring when it is stretched at constant temperature within its elastic limit

of a sample of water when it evaporates from a rain puddle on a hot day.

State what is meant by the internal energy of a system.

By reference to intermolecular forces, explain why the change in internal energy of an ideal gas is equal to the change in total kinetic energy of its molecules.

State and explain the change, if any, in the internal energy of a solid metal ball as it falls under gravity in a vacuum.

a lump of solid lead as it melts at constant temperature

some gas in a toy balloon when the balloon bursts and no thermal energy enters or leaves the gas.