Which chemical interaction causes both adhesion and cohesion in water?

• A. Ionic bonds
• B. Hydrogen bonding
• C. Van der Waals forces only
• D. Covalent bonds within a dust particle

Answer: (B)

Hydrogen bonding is the key interaction that gives water both cohesion and adhesion. Water molecules have a partial negative charge on oxygen and partial positive charges on hydrogen atoms. This allows them to form hydrogen bonds with each other, which creates cohesion—water molecules sticking to other water molecules. It also lets water form bonds with polar surfaces or other substances, producing adhesion—water sticking to things like glass or plant tissues.

Ionic bonds involve transfer of electrons between ions and don’t describe how water molecules stick to themselves or to most surfaces. Covalent bonds within a dust particle are internal to the particle and don’t govern water's interactions with it. Van der Waals forces exist, but hydrogen bonding is the stronger, more directional interaction that underpins both cohesion and adhesion in water.