Surface tension is a physical property of liquids that arises from the cohesive forces between molecules, especially those at the surface. Molecules inside the liquid experience equal attraction in all directions from neighboring molecules, but surface molecules lack neighbors above them. As a result, they are pulled more strongly toward the interior of the liquid, creating a sort of “tight film” or “skin” on the surface.
This tension tries to minimize the surface area of the liquid, making the surface behave as if it were under elastic tension.
Key Features:
- Caused by intermolecular attractions, especially hydrogen bonding in water.
- Measured in force per unit length (e.g., newtons per meter).
- Stronger in liquids with stronger intermolecular forces.
Examples:
- Water droplets form spherical shapes to minimize surface area due to surface tension.
- Insects like water striders can walk on water by distributing their weight without breaking the surface.
- Capillary action and soap bubbles are also governed by surface tension.
Surface tension plays a crucial role in biological, chemical, and physical processes, influencing how liquids spread, bead up, or interact with solids and other fluids.