Question

How does electronegativity cause the polarity in water and, ultimately, enable water to form hydrogen bonds between other water molecules?

Answer 1

Oxygen is more electronegative than Hydrogen 
                                  So . . . 
When the two form covalent bonds, oxygen pulls the electrons closer and farther from hydrogen
                                   So . . .
The water molecule is polar, with oxygen more negative and hydrogen more positive.
                                   So . . .
Since opposites attract, the more negative oxygens attract the more positive hydrogens of other water molecules, forming the hydrogen bonds.