Question 1

What is the difference between an isothermal and an adiabatic process?

Accepted Answer

An isothermal process keeps temperature constant, while an adiabatic process allows no heat transfer between the system and surroundings. For an ideal gas, an isothermal process has delta U = 0, whereas adiabatic compression increases internal energy, temperature and pressure.

Question 2

Why does an ideal gas have zero change in internal energy during an isothermal process?

Accepted Answer

For an ideal gas, internal energy depends only on temperature. Since temperature remains constant during an isothermal process, delta U is zero. Under the chemistry sign convention, work done on the gas is positive and heat rejected to the surroundings is negative, so Q = -w.

Question 3

Why is an adiabatic P-V curve steeper than an isotherm?

Accepted Answer

For a reversible ideal-gas process, an isotherm follows PV = constant, while an adiabat follows PV^gamma = constant, where gamma is greater than one. Starting from the same state, an adiabat has a higher pressure than an isotherm during compression and a lower pressure during expansion.

Question 4

Does removing an insulating jacket automatically make a process isothermal?

Accepted Answer

No. Removing insulation only makes heat transfer possible. Temperature remains constant only when heat exchange is controlled by a constant-temperature bath or another suitable heat-transfer mechanism, so a gas may still change temperature when the jacket is removed.

Question 5

What happens during free expansion of an ideal gas into a vacuum?

Accepted Answer

Free expansion is an irreversible adiabatic expansion: there is no heat transfer and no work against an external pressure. Thus Q = 0 and w = 0. The first law gives delta U = 0, so the temperature of an ideal gas remains unchanged even though its pressure decreases.

Isothermal vs Adiabatic 3D Lab — Two Cylinders, One Piston Move

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