Which of the following statements is true about the physical properties of compounds in a homologous series?

Correct option is C

Correct Answer: (C) They have a regular change in melting and boiling points

Explanation:

• Compounds in a homologous series are organic compounds that share a common functional group and differ by a CH₂ unit in their molecular structure.
• As a result, their physical properties, such as melting points and boiling points, exhibit a regular pattern of change as the molecular size (number of carbon atoms) increases.

Other Option:

•  They have identical melting and boiling points: This is incorrect. While compounds in a homologous series show a pattern, they do not have identical melting and boiling points.
• Their boiling points decrease as the number of carbon atoms increase: This is incorrect. As the number of carbon atoms increases, the boiling points increase, not decrease, because larger molecules have stronger intermolecular forces.
•  Their physical properties do not change: This is incorrect. Physical properties like boiling and melting points change in a regular manner as the size of the molecule changes in a homologous series.