Question

why does warer boil at a higher temp then nh3 when they are both dipole dipole?

Answer 1

Oxygen has a higher electronegativity than N; therefore, the water dipole is stronger than the NH3 dipole. O is about 3.5 and N about 3.0.

Answer 2

To continue or add on to DrBob's explanation, hydrogen bonding due to O-H groups is stronger than hydrogen bonding involving N-H groups. That is probably related to the electronegativity differences mentioned by DrBob.Hydrogen bonding is the main intermolecular force in both H2O and NH3. The higher boiling point of water is due to stronger hydrogen bonding in water.