Adhesion
Definition and meaning of Adhesion in chemistry.
Adhesion is the attractive force between molecules of two different substances that causes them to stick together across an interface. This occurs when intermolecular forces, including van der Waals forces, hydrogen bonding, or electrostatic interactions, act between the surfaces of dissimilar materials.
In more detail
Adhesion differs fundamentally from cohesion, which is the attraction between molecules of the same substance. The strength of adhesive forces depends on the polarity of the molecules, their ability to form hydrogen bonds, and how closely the surfaces can approach each other. Adhesion is critical in everyday applications: glues bond materials, paint coats surfaces, and capillary action transports liquids against gravity. Understanding adhesion helps engineers and chemists select or design materials that stick properly without damaging substrates.
Key facts
| Field | Physical Chemistry |
|---|---|
| Related forces | van der Waals forces, hydrogen bonding, electrostatic interactions |
| Contrasts with | Cohesion (attraction within a substance) |
| Key factor | Surface polarity and intermolecular contact distance |
Water adheres strongly to clean glass because the polar water molecules form hydrogen bonds with the silica (SiO2) in the glass surface, causing water to climb the walls of a graduated cylinder and form a concave meniscus.
Frequently asked questions
How is adhesion different from cohesion?
Adhesion is the attraction between molecules of different substances, while cohesion is the attraction between molecules of the same substance.
What causes water to stick to glass?
Water adheres to glass through hydrogen bonding between polar water molecules and the silica in the glass surface.