Why does the land in a desert get hotter during the day and colder at night quickly?

Water is used to cool radiators of engines,because

The density of a material $A$ is $1500 \ kg/m^3$ and that of another material $B$ is $2000 \ kg/m^3$. It is found that the heat capacity of $8$ volumes of $A$ is equal to the heat capacity of $12$ volumes of $B$. The ratio of specific heats of $A$ and $B$ will be

The quantities of heat required to raise the temperature of two solid copper spheres of radii $r_{1}$ and $r_{2}$ $(r_{1} = 1.5 r_{2})$ through $1 \ K$ are in the ratio:

The thermal capacity of $40\, g$ of aluminium (specific heat $= 0.2\, cal/g/^{\circ}C$) is ........ $cal/^{\circ}C$.

The temperature of $5$ moles of a gas which was held at constant volume was changed from $100^{\circ}C$ to $120^{\circ}C$. The change in internal energy was found to be $80$ Joules. The total heat capacity of the gas at constant volume will be equal to ...... $J/K$.