Is the melting of ice an adiabatic or an isothermal process?

The work done by an ideal gas of $2 \text{ moles}$ in increasing its volume from $V$ to $2V$ at constant temperature $T$ is $W$. The work done by an ideal gas of $4 \text{ moles}$ in increasing its volume from $V$ to $8V$ at constant temperature $\frac{T}{2}$ is:

The work done to increase the volume of $2$ moles of an ideal gas from $V$ to $2V$ at a constant temperature $T$ is $W$. The work to be done to increase the volume of $2$ moles of the same gas from $2V$ to $4V$ at the same constant temperature $T$ is:

The isothermal elasticity of a gas is equal to

$A$ thermodynamic process in which the temperature $T$ of the system remains constant,although other variables $P$ and $V$ may change,is called:

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