Adhesion and Cohesion of Water

Water molecules are attracted to each other, this is known as cohesion. This attraction arises from electrostatic interactions known as hydrogen bonds. Hydrogen bonds, between water molecules, are intermolecular forces that form between the partially negative oxygen atom from one molecule to a partially positive hydrogen atom from another water molecule. This causes the water molecules to ‘stick’ to each other. Have you ever noticed droplets of water on a leaf? This is caused by the cohesion of water.

Figure 1: Cohesion and adhesion of water molecules.

Sometimes, water has an even stronger attraction to other molecules than itself. This is known as adhesion, and occurs with other polar and charged molecules. The principle is the same for cohesion, where water forms hydrogen bonds, but rather than forming hydrogen bonds with water molecules, it forms them with molecules of another kind.