Identify the correct statement.

(1) The molecules of water move faster than ice.

(2) The molecules are more closely packed in ice than water.

(3) The molecules of water vibrate to and fro only but those of ice are free to move within the boundary of the vessel in which it is kept.

(4) The molecules have more intermolecular space in ice than in water.

1. (1), (2) and (3)
2. (2), (3) and (4)
3. (1) and (2)
4. all are correct

Assertion (A) : We often pour tea in a saucer to cool it faster.

Reason (R) : Evaporation takes place at all temperatures.

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

Fill in the blanks:

(a) Evaporation takes place at …………… temperatures.

(b) …………… process is just the reverse of melting.

(c) …………… is a process that involves direct conversion of a solid into its vapour on heating.

(d) The temperature at which a solid converts into a liquid is called its …………… .

(e) The smallest unit of matter that exists freely in nature is called …………… .

(f) Molecules of a substance are always in a state of …………… and so they possess …………… .

(g) Inter-molecular space is maximum in …………… less in …………… and the least in …………… .

(h) Inter-molecular force of attraction is maximum in …………… , less in …………… and the least in …………… .

Write true of false for each statement:

(a) The temperature of a substance remains unaffected during its change of state.

(b) Ice melts at 100°C.

(c) Water at 100°C has more heat than steam at 100°C.

(d) Evaporation of a liquid causes cooling.

(e) Water evaporates only at 100°C.

(f) Boiling takes place at all temperatures.

(g) Evaporation takes place over the entire mass of the liquid.

(h) The process of a gas converting directly into solid is called vaporization.

(i) At high altitudes, water boils above 100°C.

(j) The melting point of ice is 0°C.