Answer: Because of the polarity of water molecules
Molecular cohesion is the attraction that molecules have for others of their same type. Depending on the intensity of this attraction, a substance is in a solid, liquid or gaseous state.
In this sense, water ([tex]H_{2}O[/tex]) can stick to itself through hydrogen bonds, because a water molecule consists of 2 hydrogen atoms attached to 1 oxygen atom.
The oxygen atom tends to monopolize more electrons and keeps them away from hydrogen. Then, it can be said that a water molecule will have a negative side (oxygen) and a positive side (hydrogen).
Thanks to this polarity, water molecules can stick together with the formation of hydrogen bonds to attract a partial positive charge of hydrogen and a more electronegative atom, such as oxygen.
