what is the difference between cohesion amd adhesion?
Cohesion is the attraction between molecules of the same substance, while adhesion is the attraction between molecules of different substances. Cohesion causes water molecules to stick together, creating surface tension, while adhesion causes water to stick to the inside of a tube or to another surface.
Cohesion and adhesion are two types of forces that exist between molecules or particles. The main difference between cohesion and adhesion lies in the nature of the substances and the way they interact with each other. Here is a step-by-step explanation of the difference between cohesion and adhesion:
1. Definition of Cohesion: Cohesion refers to the intermolecular attraction between similar molecules. It is the force that holds molecules of the same substance together. For example, the cohesion between water molecules allows them to stick together and form droplets.
2. Definition of Adhesion: Adhesion refers to the intermolecular attraction between different molecules. It is the force of attraction between molecules of different substances. For example, the adhesion between water and the inner surface of a glass causes the water to "stick" to the sides of the glass.
3. Nature of Substances: Cohesion occurs within a single substance, where the intermolecular forces hold the molecules together. Adhesion occurs between two different substances, where the intermolecular forces attract the molecules of different substances to each other.
4. Molecular Interactions: In cohesion, the attractive forces are primarily caused by intermolecular forces such as hydrogen bonding, van der Waals forces, or dipole-dipole interactions between molecules of the same substance. In adhesion, the attractive forces are also caused by intermolecular forces between molecules, but these forces can be different depending on the substances involved.
5. Surface Tension: Cohesion determines the surface tension of a liquid, which is the tendency of the surface of a liquid to minimize its surface area. It is responsible for the formation of droplets and capillary action. Adhesion, on the other hand, affects the wetting ability of a liquid on a solid surface, leading to phenomena like water sticking to the inner surface of a glass.
In summary, cohesion is the intermolecular force within a substance that holds similar molecules together, while adhesion is the intermolecular force between different substances that causes them to stick to each other.