The first law of thermodynamics confirms the law of . . . . . . .

Is it possible to convert internal energy into work or mechanical energy?

In changing the state of a thermodynamic system from state $A$ to state $B$, the heat supplied to the system is $Q$ and the work done by the system is $W$. The change in its internal energy is

$A$ cylinder with a piston of unit cross-sectional area contains one mole of an ideal gas as shown in the figure. $A$ spring of unstretched length $L$ and spring constant $K$ is connected between the piston and the bottom of the cylinder. Initially, the spring is unstretched and the gas is in equilibrium. When an amount of heat $Q$ is supplied to the gas, its volume changes from $V_0$ to $V_1$. Find:
$(a)$ The initial pressure of the system.
$(b)$ The final pressure of the system.
$(c)$ Using the first law of thermodynamics, find the relation between $Q, V_0, V_1, P_a$ and $K$.

Consider one mole of perfect gas in a cylinder of unit cross-section with a piston attached as shown in the figure. $A$ spring (spring constant $k$) is attached (unstretched length $L$) to the piston and to the bottom of the cylinder. Initially,the spring is unstretched and the gas is in equilibrium. $A$ certain amount of heat $Q$ is supplied to the gas,causing an increase in volume from $V_0$ to $V_1$.
$(a)$ What is the initial pressure of the system?
$(b)$ What is the final pressure of the system?
$(c)$ Using the first law of thermodynamics,write down a relation between $Q, V_0, V_1, P_a$ and $k$.

$1\;g$ of water,of volume $1\;cm^{3}$ at $100^{\circ}C$,is converted into steam at the same temperature under normal atmospheric pressure $(=1 \times 10^{5}\;Pa)$. The volume of steam formed equals $1671\;cm^{3}$. If the specific latent heat of vaporisation of water is $2256\;J/g$,the change in internal energy is.....$J$.