Question

1. What is meant by inter-molecular forces of attraction ? How do they vary in solids, liquids and
EXERCISES
Answer the following questions in about twenty words.
gases ?
2. Why does water in a dish evaporate faster then in a bottle ?
3. What do you mean by sublimation and deposition ?
4. Why does the size of naphthalene balls decrease when left open ?
5. Water remains cool in earthern pots in hot summer days.​

Answer 1

Answer:

The force between molecules which keep them together or space between molecules is called intermolecular force of attraction.

1. Solids have strong intermolecular force of attraction as a result they are tightly packed.

2. Liquids have weak intermolecular force of attraction as a result they are loosely packed.

3. Gases have very weak intermolecular force of attraction as a result they are very very loosely packed.

2. Evaporation is surface phenomenon as a result when a liquid is kept on a dish it evaporates faster than when kept in a bottle. the particles at the surface gain enough energy to evaporate faster. As a result when spread open in the dish, they evaporate faster than when kept in a bottle.

3. The conversion of solid to gases directly without passing through liquid state is called sublimation.

The conversion of gases to solid directly without passing through liquid state is called deposition.

4. Naphthalene balls decrease in size day by day due to the process of sublimation. From the state of solid they get converted to gases and evaporate slowly.

5. Evaporation leads to cooling. Water evaporates quicker through earthen pots. Thus water near the pores of the pot gain energy and evaporaye giving a cooling effect to water. Thus, water stays cool even in summers when kept in earthen pots.

Answer 2

Answer:

2. Water in a dish evaporate faster than in a bottle because surface area of the water spread on dish is more than that of water kept in bottle.

3.Some substances that transition from a solid to a gas and skip the liquid phase entirely at standard conditions. This change form a solid to a gas is called sublimation. The reverse process of a gas going to a solid is known as deposition.