How are hydrogen bonds formed in water?

Hydrogen bonds in water are formed due to the electrostatic interactions between the positive end of a water molecule (the hydrogen atoms) and the negative end of another (the oxygen atom). Water consists of two hydrogen atoms covalently bonded to one oxygen atom, resulting in a polar molecule. This polarity arises because oxygen is more electronegative than hydrogen, causing the oxygen atom to hold a partial negative charge and the hydrogen atoms to have a partial positive charge.

When water molecules come into close proximity, the positive hydrogen end of one molecule is attracted to the negative oxygen end of another molecule. This attraction is what we refer to as a hydrogen bond. Hydrogen bonds are essential in giving water many of its unique properties, including high surface tension, specific heat capacity, and solvent capabilities, which are crucial for biochemical processes.

The other choices describe different types of interactions that do not apply to the formation of hydrogen bonds in water: covalent bonding involves the sharing of electron pairs between atoms, ionic interactions involve the attraction between fully charged ions, and van der Waals forces are weak attractions that occur between all molecules but are not responsible for the strong hydrogen bonding observed in water.