In an experiment to determine the specific latent heat of fusion of ice '$\mathrm{L}$ by the method of mixtures, the following measurements were taken:

Mass of calorimeter $+$ Stirrer $=x \mathrm{kg}$

Mass of water $=y \mathrm{kg}$

Initial temperature of water $=t_1°\mathrm{C}$

Final temperature of mixture $=t_2°\mathrm{C}$

Mass of ice method $=M \mathrm{kg}$

(Given S.H.C. of calorimeter and water are ${\mathrm{S}}_1$ and $S_{\mathit{2}}$ respectively)

Express $\text{'}\mathrm{L}\text{'}$ in terms of above data.

A metal cylinder of $20 \mathrm{g}$ is heated to a steady temperature of ${100}^{°}\mathrm{C}$ and then dropped into a calorimeter of mass $50 \mathrm{g}$ containing $70 \mathrm{g}$ of water of ${20}^{°}\mathrm{C}$. After stirring, the highest steady temperature of the mixture is observed to be ${23}^{°}\mathrm{C}$. Write the value of specific heat capacity of the metal of the cylinder to the nearest integer(in $\mathrm{J} {\mathrm{kg}}^{-1} {\mathrm{K}}^{-1}$).

(specific heat capacity of water $=4200 \mathrm{J} {\mathrm{kg}}^{-1} {\mathrm{K}}^{-1}$, specific heat capacity of calorimeter (copper) $=400 \mathrm{J} {\mathrm{kg}}^{-1} {\mathrm{K}}^{-1}$).

Note: Write only numeric value.

During the change of state of a substance, the temperature remains unchanged, although the heat is supplied or withdrawn. Explain it on the basis of kinetic theory. Explain the physical difference between solids, liquids and gases on the basis of molecular forces.

Draw a neat and labelled diagram of temperature versus time, when a substance like naphthalene is heated from $0 °\mathrm{C} \mathrm{to} 100 °\mathrm{C}$. Also, draw another curve when the molten substance cools to room temperature. How will you determine the melting point and freezing point from the graphs drawn?

Explain why, with reference to high latent heat of fusion of ice: Rivers fed by water from snow covered mountains are not likely to dry up in summer.

Explain why, with reference to high latent heat of fusion of ice:

Weather may become chilly when snow in the mountains starts melting at the end of the winter season.