Chapter 3, Problem 1ALQ

When water boils, you can see bubbles rising to the surface of the water. Of what arc these bubbles made?

1. air
2. hydrogen and oxygen gas
3. oxygen gas
4. water vapor
5. carbon dioxide gas

Interpretation Introduction

Interpretation:

On boiling the water, bubbles rises to the surface of the water, the composition of the bubbles should be determined.

Concept Introduction:

The composition of water is hydrogen and oxygen. The chemical formula is ${\text{H}}_{\text{2}}\text{O}$. The boiling point of water is $100{}^{\circ }\mathrm{C}$ thus, at $100{}^{\circ }\mathrm{C}$ water is present in both the states that is liquid as well as gas or water vapor.

Answer to Problem 1ALQ

Water vapour. Thus, option (d) is correct.

Explanation of Solution

Reason for correct option:

On boiling water, water gains heat and the state of water changes from liquid to gas, which is present in water bubble. The gas state of water is water vapor thus, the bubbles are made up of water vapor and option (d) is correct.

Conclusion

Near the surface of water, due to increase in temperature, density of air decreases and it escapes from the region thus, it can not present in the bubbles. Water does not contain carbon dioxide gas thus, it cannot be there. On boiling, water does not split into hydrogen and oxygen gas thus, bubbles cannot be made up of hydrogen and oxygen.

Therefore, option (a), (b), (c) and (e) are incorrect.