How do you identify functional groups in a compound?

There are many functional groups present in organic molecules.  The ability to identify them relies on practice and knowing the characteristics and purpose of each functional group.  Examples of functional groups are: hydroxyl, carbonyl, carboxyl, amino, phosphate, sulfhydryl.  I encourage you to research on each of the different groups to understand their purpose, characteristics, and structure as it is the best way to learn to distinguish between them.

They became more resistant.