The melting point of naphthalene is 80°C and the room temperature is 30°C. A sample of liquid naphthalene at 100°C is cooled down to the room temperature. Draw a temperature time graph to represent this cooling. In the graph, mark the region which corresponds to the freezing process.

104 g of water at 30°C is taken in a calorimeter made of copper of mass 42 g. When a certain mass of ice at 0°C is added to it, the final steady temperature of the mixture after the ice has melted, was found to be 10°C. Find the mass of ice added.
[Specific heat capacity of water = 4.2 J g^-1 °C^-1; Specific latent heat of fusion of ice = 336 J g^-1; Specific heat capacity of copper = 0.4 J g^-1 °C^-1 ]

(i) Define nuclear fission.

(ii) Rewrite and complete the following nuclear reaction by filling in the atomic number of Ba and mass number of Kr :

${}_{92}^{235}\text{U}${92}^{235}\text{U} + ${0}^{1}\text{n}$ ⟶ ${}_{\mathrm{.}\mathrm{.}\mathrm{.}}^{144}\text{Ba}${…}^{144}\text{Ba} + ${36}^{…}\text{Kr}$ + 3 $_{0}^{1}\text{n}$ + Energy

The diagram below shows a magnetic needle kept just below the conductor AB which is kept in North South direction.

(i) In which direction does the needle deflect when the key is closed ?

(ii) Why is the deflection produced?

(iii) What will be the change in the deflection if the magnetic needle is taken just above the conductor AB ?

(iv) Name one device which works on this principle.