What is a functional group and how does it differ from a homologous series? Provide an example of each.

A functional group is a specific group of atoms that imparts characteristic properties and reactions to an organic compound, such as -OH in alcohols. A homologous series is a sequence of compounds that share the same functional group and have a gradual change in physical properties, like the alkanes (e.g., methane, ethane, propane). The key difference is that functional groups define the reactivity of individual compounds, while homologous series categorize compounds based on shared functional groups.

This answer effectively defines both concepts and identifies their key difference. It provides clear examples, illustrating how functional groups determine the behavior of specific compounds, whereas homologous series group compounds with similar properties. This understanding is essential for students studying organic chemistry.