Chapter U2.46, Problem 1E

Interpretation Introduction

Interpretation : Substances that are expected to have smell are to be explained.

Concept Introduction :

Molecules smell differently. Humans are not able to smell some molecules. Some molecules are small and some are large; some are polar and some are nonpolar. Some molecules have metallic bonding while some have ionic bonding. Some molecules are made of metals while some are made of nonmetals or both metal and non-metal.

Answer to Problem 1E

Substances that one would expect to have a smell are:

1. Those that are in gaseous form
2. Those that have molecular covalent bonding
3. Small polar molecules
4. Non-polar molecules.

Explanation of Solution

Substances that one would expect to have a smell are:

1. Those that are in gaseous form- Molecules that can exist in gaseous form can be smelled easily as they can easily reach to the receptor sites of our nose.
2. Those that have molecular covalent bonding- Molecules that have molecular covalent bonding are made of nonmetals. These can exist in solid, liquid or gaseous state. These substances can easily form gases at room temperature. They can enter our nose easily and can be detected by the receptor sites.
3. Small polar molecules- Small molecules like ammonia that are polar have smell. Small molecules are gases at room temperature. These molecules can bind easily to the receptor sites.
4. Moderate size molecules- Most moderate sized molecules having 5 to 19 carbon atoms will smell irrespective of whether they are polar or nonpolar because carbon bonds easily to other carbon atoms and forms long complex molecules. They form a liquid but they are volatile; that is they can easily enter gas phase. Gases can be easily detected by the receptor sites of our nose as smell.

Conclusion

Generally gases have smell. Small polar molecules have smell and all moderate sized molecules have smell.