An ideal gas in a cylinder is separated by a piston in such a way that the entropy of one part is $S_{1}$ and that of the other part is $S_{2}$. Given that $S_{1} > S_{2}$. If the piston is removed,then the total entropy of the system will be:

$A$ solid body of constant heat capacity $1\,J/^{\circ}C$ is being heated by keeping it in contact with reservoirs in two ways:
$(i)$ Sequentially keeping in contact with $2$ reservoirs such that each reservoir supplies the same amount of heat.
$(ii)$ Sequentially keeping in contact with $8$ reservoirs such that each reservoir supplies the same amount of heat.
In both cases, the body is brought from an initial temperature $100^{\circ}C$ to a final temperature $200^{\circ}C$. The entropy change of the body in the two cases respectively is:

Why is a heat engine never $100\%$ efficient?

"Heat cannot flow by itself from a body at a lower temperature to a body at a higher temperature". This statement corresponds to:

State the Kelvin-Planck statement of the second law of thermodynamics.

During phase change,entropy