Here's why:
* Polarity: Water molecules are polar, meaning they have a slightly positive end (hydrogen atoms) and a slightly negative end (oxygen atom).
* Electrostatic attraction: The positive end of one water molecule is attracted to the negative end of another water molecule. This attraction is due to electrostatic forces between the oppositely charged ends.
* Hydrogen bond: The specific type of electrostatic attraction between a hydrogen atom and a highly electronegative atom (like oxygen) is called a hydrogen bond.
Hydrogen bonds are relatively weak compared to covalent bonds, but they are strong enough to hold water molecules together, giving water many of its unique properties like high boiling point and surface tension.
