Chapter U2.18, Problem 5E

Interpretation Introduction

Interpretation : Water being a small polar molecule does not smell. The reason for this exception has to be explained.

Concept Introduction :

Molecules smell differently. The chemistry behind smell is very complicated. Small molecules that are polar in nature have a smell. Small molecules that are nonpolar do not have a smell.

Answer to Problem 5E

Water being a small and polar molecule does not have a smell because the receptor sites in our nose are continuously exposed to the water molecules. The mucous membrane also mostly contains water. So they do not feel the difference in smell.

Explanation of Solution

Polar molecules dissolve in the mucous membrane of the nose and then attach to the receptor sites. After the polar molecules enter the nose they are attracted to the receptor sites in the nose. The small polar molecules stick to the polar part of the receptor site.

Our nose has receptor sites that are continuously exposed to water all the time. Thus, they do not feel the difference in smell.

Conclusion

Small polar molecules generally have smell with some exceptions like water. Humans cannot smell water due to too much exposure to water all the time. The smell of water is hard to detect.