Does the internal energy of an ideal gas change in an isothermal process?

$A$ cylinder fitted with a piston contains $0.2 \, moles$ of air at a temperature of $27^{\circ}C$. The piston is pushed so slowly that the air within the cylinder remains in thermal equilibrium with the surroundings. Find the approximate work done by the system if the final volume is twice the initial volume (in $J$).

The change in the entropy of $1$ mole of an ideal gas which undergoes an isothermal process from an initial state $(P_1, V_1, T)$ to the final state $(P_2, V_2, T)$ is equal to

In which of the processes does the internal energy of the system remain constant?

An isothermal process has a non-linear graph between:

When heat is given to a gas in an isothermal change,the result will be