Which law of thermodynamics provides the definition of temperature?

Two moles of an ideal gas are expanded isothermally from $15 \ dm^3$ to $20 \ dm^3$. If the amount of work done is $-6 \ dm^3 \ bar$,find the external pressure needed to obtain this work.

Fill in the blanks:
$(i)$ The conversion of graphite into diamond is a ........ process.
$(ii)$ $1 \text{ calorie} = ........ \text{ Joules}$.
$(iii)$ Work done by the system can be calculated by the equation ........ .
$(iv)$ The change in heat energy during a chemical reaction at constant volume is called ........ .

An ideal gas undergoes a cyclic transformation starting from the point $A$ and coming back to the same point by tracing the path $A$ $\rightarrow B$ $\rightarrow C$ $\rightarrow D$ $\rightarrow A$ as shown in the three cases above. Choose the correct option regarding $\Delta U$.

An adiabatic process is .................

Which of the following processes exhibits $\Delta U = 0$?