How would you determine whether a sample of an unknown organic compound was a fatty acid, aldehyde, ketone, or alcohol?
A few key words, if I have some time I'll elaborate it tomorrow during work.
Fatty acid: 1. low pH
2. water soluble in alkaline solutions
not soluble anymore if you become acidic
(depending on chain length)
Aldehyde: Fehling test (something about oxidizing)
Ketone: you take Di-phenyl-hydrazine, condense it to your ketone to get a Di-phenyl-hydrazone. (a colorful precipitate?)
Alcohol: Lucas test. It even tells you if it's 1°, 2°, or 3°. How it works: no idea (I always forget that)
Maybe the keywords already help you a little bit.