Chapter U2, Problem SIII5RE

Interpretation Introduction

Interpretation : The reason due to which one cannot smell a perfume while the bottle is closed but can smell it once the bottle is opened needs to be explained.

Concept Introduction : Some substances have smell. The process of smelling involves interaction between molecules. To smell a substance, its molecules must be air borne and must reach the receptor sites of nose. Receptor sites have polar areas that bind to polar molecules.

Answer to Problem SIII5RE

A bottle of perfume contains a liquid. This liquid has medium sized molecules that must undergo a phase change to show smell. When the bottle is closed one cannot smell it as the perfume cannot reach our nose. When the bottle is opened, some molecules of perfume vaporize and enter into gas phase. These vapors reach our nose and bind with the receptor sites.

Explanation of Solution

Perfume contains a liquid which has medium sized molecules. All medium sized molecules can show smell whether they are polar or nonpolar. These molecules are attracted to one another and so they occur as a liquid but they are volatile, meaning they can go easily into gas phase.

When the bottle is closed one cannot smell it as the perfume cannot reach our nose. When the bottle is opened, some molecules of perfume vaporize and enter into gas phase. These vapors reach our nose and bind with the receptor sites.

Conclusion

One can smell a molecule only when it occurs in a gas phase and enters into our nose where it must bind to the polar end of the receptor site.