Assertion (A): Naphthalene balls become smaller with the passage of time, as they sublime.

Reason (R): Naphthalene balls sublime, as such solids have stronger intermolecular forces of attraction in comparison to other solids.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Assertion (A): Conversion of a substance in solid state to its liquid state is called melting.

Reason (R): On heating, the kinetic energy of solid molecules increases.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Fill in the blanks:

(a) The change of a solid into a liquid is called …………… .

(b) The process in which a solid directly changes into gas is called …………… .

(c) The change of water vapour into water is called …………… .

(d) The temperature at which a liquid starts changing into its vapour state is …………… .

(e) A gas can be changed into a liquid and then into solid by ............... its pressure and cooling .

(f) LPG cylinders contain cooking gas in ............... state at high pressure.

(g) In a chemical reaction, the total mass of the reactants is ............... to the total mass of the products.

Write whether the following statements are true or false.

(a) Matter can be created or destroyed during a chemical reaction.

(b) When a substance changes its state, its mass is also changed.

(c) In solids, the molecules can only vibrate about their mean positions. They are not free to move.

(d) In liquids, the kinetic energy of molecules is less than that of solids.

(e) In gases, the intermolecular forces of attraction are negligible.