Question

how do you tell if an amino acid is hydrophobic or hydrophillic?

Answer 1

You look at the side chain :)
http://en.wikipedia.org/wiki/Proteinogenic_amino_acid#Side_chain_properties

Answer 2

If you see lots of non polar bonds like C-H, then that indicates that the amino acid is highly hydrophobic. If you see lots of polar bonds like O-H, N-H, then the amino acid is highly hydrophillic. Hope this helps :)

Answer 3

This will depend of the structure of the molecule, it's atomic constitution, display and it's distribution of eletrons...