In how many ways can the internal energy of a system be changed?

$A$ thermodynamic system absorbs $2 \, kcal$ of heat and performs $500 \, J$ of work. The change in its internal energy is ......... $J$.

Write and explain the first law of thermodynamics.

In supplying $400$ calories of heat to a system,the work done will be

If the amount of heat given to a system is $35 \ J$ and the amount of work done by the system is $-15 \ J$,then the change in the internal energy of the system is .... $J$.

$A$ sample of $0.1 \, g$ of water at $100^{\circ} C$ and normal pressure $(1.013 \times 10^5 \, N m^{-2})$ requires $54 \, cal$ of heat energy to convert to steam at $100^{\circ} C$. If the volume of the steam produced is $167.1 \, cc$,the change in internal energy of the sample is ....... $J$.