Why are water molecules polar?

Water molecules are polar because they have a bent shape and uneven distribution of charge.

Water, or H2O, is a molecule made up of two hydrogen atoms and one oxygen atom. The structure of a water molecule is not linear but bent. This is due to the presence of two lone pairs of electrons on the oxygen atom, which repel the bonds holding the hydrogen atoms, causing them to be pushed downwards and creating a bent shape.

The oxygen atom is more electronegative than the hydrogen atoms. Electronegativity is a measure of how strongly an atom can attract a bonding pair of electrons. In water, the oxygen atom attracts the bonding electrons more strongly than the hydrogen atoms, pulling the electrons closer to itself. This results in a partial negative charge (δ-) on the oxygen atom and a partial positive charge (δ+) on each hydrogen atom.

This uneven distribution of charge within the molecule, with the oxygen side being slightly negative and the hydrogen side being slightly positive, makes water a polar molecule. The polarity of water molecules is responsible for many of its unique properties, such as its ability to dissolve many substances (solvent properties), its high boiling point compared to molecules of similar size, and its ability to form hydrogen bonds with other molecules.

In summary, the polarity of water molecules is due to their bent shape and the difference in electronegativity between the oxygen and hydrogen atoms, which results in an uneven distribution of charge.