Chapter 12, Problem 1SAQ

The first diagram shown here represents liquid water. Which of the diagrams that follow best represents the water after it has boiled?

Interpretation Introduction

Interpretation:

The correct representation of water after it has boiled is to be identified from the given options.

Concept introduction:

When the water boils, it changes its liquid state to gaseous state. This process is called as evaporation. Evaporation is a surface phenomenon which increases with increase in surface area and temperature. Surface area of molecules increases with decrease in strength of intermolecular forces.

Answer to Problem 1SAQ

Correct answer: Option (a)

Explanation of Solution

Reasons for correct option:

When the water boils, its constituent particles which were initially close, fall apart. With increase in thermal energy there is increase in surface area and decrease in strength of intermolecular forces between water molecules. The molecules of water fall apart andtend to leave the surface of water due to weak intermolecular forces. Thus, evaporation of water take place and the number of molecules of water gets decreased.

Hence, option (a) is correct.

Reasons for incorrect options

Option (b)is incorrect because the figure shows the breakdown of water molecules upon boiling. So, it is a wrong answer.

Option (c)is incorrect because the figure shows the breakdown of water molecules when it is boiled. This does not take place because only the distances between the particles changes when it is converted to steam. So, it is a wrong answer.

Hence, options (b) and (c) are incorrect.