One mole of an ideal gas at $300 \ K$ in thermal contact with surroundings expands isothermally from $1.0 \ L$ to $2.0 \ L$ against a constant external pressure of $3.0 \ atm$. In this process,the change in entropy of the surroundings $(\Delta S_{\text{surr}})$ in $J \ K^{-1}$ is $(1 \ L \ atm = 101.3 \ J)$.

$A$ 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:

Water of mass $m$ gram is slowly heated to increase the temperature from $T_1$ to $T_2$. The change in entropy of the water,given specific heat of water is $1 \ J \ g^{-1} \ K^{-1}$,is

$A$ hot piece of copper at $100^{\circ} C$ is dropped into a pond at $30^{\circ} C$. The copper cools down to $30^{\circ} C$,while the pond remains at its initial temperature due to its large size. Then,

$N_{2}$ gas is heated from $300\, K$ to $600\, K$ through an isobaric process. Find the change in entropy of the gas. $(n = 1\, \text{mole})$ (in $J/K$)

“Heat cannot by itself flow from a body at lower temperature to a body at higher temperature” is a statement or consequence of