$A$ refrigerator converts $500\,g$ of water at $25\,^{\circ}C$ into ice at $-10\,^{\circ}C$ in $3\,hours\,40\,minutes$. The quantity of heat removed per minute is ........ $cal/\min$.
(Specific heat of water $= 1\,cal/g\,^{\circ}C$,Specific heat of ice $= 0.5\,cal/g\,^{\circ}C$,Latent heat of fusion $= 80\,cal/g$)

Find the difference in temperature between the water at the top and the bottom of a $20 \ m$ high waterfall, assuming $10 \%$ of the energy of the fall is spent in heating the water. [Use specific heat capacity of water $= 4000 \ J \ kg^{-1} K^{-1}$ and $g = 10 \ m/s^2$]. (in $^{\circ} C$)

What is sublimation? Give names of sublimable substances.

Explain why:
$(a)$ Two bodies at different temperatures $T_1$ and $T_2$,if brought in thermal contact,do not necessarily settle to the mean temperature $(T_1 + T_2) / 2$.
$(b)$ The coolant in a chemical or a nuclear plant (i.e.,the liquid used to prevent the different parts of a plant from getting too hot) should have high specific heat.
$(c)$ Air pressure in a car tyre increases during driving.
$(d)$ The climate of a harbour town is more temperate than that of a town in a desert at the same latitude.

The ratio of the coefficient of volume expansion of a glass container to that of a viscous liquid kept inside the container is $1 : 4$. What fraction of the inner volume of the container should the liquid occupy so that the volume of the remaining vacant space will be same at all temperatures?

$A$ stationary object at $4^{\circ}C$ and weighing $3.5\, kg$ falls from a height of $2000\, m$ on a snow mountain at $0^{\circ}C$. If the temperature of the object just before hitting the snow is $0^{\circ}C$ and the object comes to rest immediately $(g = 10\, m/s^2)$ and (latent heat of ice $= 3.5 \times 10^5\, J/kg$),then the amount of ice that will melt is: