1) it has a hydrocarbon chain or ring in its R-group; this will make it insoluble in water (and thus non-polar).
2) it has a charge (- or +) in its amino group; this will make it non-polar.
3) it has an electronegative atom (like oxygen) in its carboxyl group; this will classify it as polar.
4) it has a charge (- or +) in its R-group; this will make it polar.
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