Water is because oxygen is more electronegative than hydrogen.

water is polar because oxygen is more electronegative than hydrogen

Explanation:

Water is  polar covalent compound because of large electronegativity difference between oxygen and hydrogen. If the electronegativity difference is 0.4 or less than 0.4 the covalent compound will be non polar.

Covalent Compound:

It is formed by the sharing of electron pair between bonded atoms.  

The atom with larger electronegativity attract the electron pair more towards it self and becomes partial negative while the other atom becomes partial positive.

For example:

In water the electronegativity of oxygen is 3.44 and hydrogen is 2.2. That's why electron pair attracted more towards oxygen, thus oxygen becomes partial negative and hydrogen becomes partial positive and water becomes polar.

1.43 x 10^-11 j the guy commented the awnser just making sure u see it .