Question

What do you call a long-chain organic molecule with a polar group on one or both ends of the molecule?

Answer 1

Is called a SURFACTANT.

Explanation:

Surfactants are long chain organic molecules (typically acids, or so-called fatty acids), with a polar end, typically carboxylate groups, `RC(=O)O^(-)Na^+` (or a polar group on both end). They can thus interact with greases (thru the alkyl chain), and also with aqueous solutions (thru the polar groups). These greatly reduce the surface tension of water.

Detergents and soaps are very common surfactants.