A quantity of ideal gas occupies an initial volume V0 at a pressure P0­ and a temperature T0. It expands to volume V1 (a) at constant pressure, (b) at constant temperature, and (c) adiabatically. Graph each case on a pV diagram, in which case is Q greatest? Least? In which case is ∆Eint greatest? Least?

(b)
Isothermal Process:-
The process in which, the change in pressure and volume takes place at constant temperature is called an isothermal change.
A quantity of ideal gas occupies an initial volume V₀ at a pressure p₀ and a temperature T₀. It expands to volume V₁ at constant temperature. The pV diagram for this process as shown in below figure 2.
Figure 2:


(c)
Adiabatic Process:-
The process in which, the change in pressure and volume and temperature takes place without any heat entering or leaving the system is called adiabatic change.
A quantity of ideal gas occupies an initial volume V₀ at a pressure p₀ and a temperature T₀. It expands to volume V₁ adiabatically. The pV diagram for this process as shown in below figure 3.
Figure 3:

Q is greatest for constant pressure process and least for adiabatic. W is greatest (in magnitude, it is negative for increasing volume process) for constant pressure process and least for adiabatic. ΔE_int is greatest for constant pressure (for which it is positive), and least for adiabatic (for which is negative).