Why is water used as a coolant in automobile radiators?

The molar mass of a substance is $50 \, g/mol$. When $300 \, J$ of heat is supplied to a $25 \, g$ sample of this substance,its temperature increases from $30^{\circ}C$ to $50^{\circ}C$. The values of heat capacity and specific heat capacity are,respectively:

The temperature of $5$ moles of a gas at constant volume is changed from $100^{\circ} C$ to $120^{\circ} C$. The change in internal energy is $80 \,J$. The total heat capacity of the gas at constant volume in $J/K$ is:

The figure below shows the variation of specific heat capacity $(C)$ of a solid as a function of temperature $(T)$. The temperature is increased continuously from $0$ to $500 \ K$ at a constant rate. Ignoring any volume change,which of the following statement$(s)$ is (are) correct to a reasonable approximation?
$(A)$ The rate at which heat is absorbed in the range $0-100 \ K$ varies linearly with temperature $T$.
$(B)$ Heat absorbed in increasing the temperature from $0-100 \ K$ is less than the heat required for increasing the temperature from $400-500 \ K$.
$(C)$ There is no change in the rate of heat absorption in the range $400-500 \ K$.
$(D)$ The rate of heat absorption increases in the range $200-300 \ K$.

If the ratio of the diameters of two spheres made of the same material is $1:2$,what is the ratio of their heat capacities?

Define specific heat capacity and write its $SI$ unit.