Surface Tension

What is Surface Tension?

Surface tension is the tendency of a liquid’s surface to behave like a stretched elastic film and minimize its surface area. It is caused by cohesive forces between the liquid molecules.

What are the Symbol and SI Unit of Surface Tension?

Surface tension is commonly represented by γ (gamma). Its SI unit is newton per meter (N/m).

What are the causes of Surface Tension?

Molecules inside a liquid are attracted in all directions by surrounding molecules. Molecules at the surface have fewer neighboring molecules above them, creating a net inward attraction. This makes the surface behave like a stretched film.

What is an Example of Surface Tension?

Surface tension allows small insects to stand on water, helps water form rounded droplets, and allows some small objects, such as a carefully placed needle, to remain on the water’s surface.

Example

A liquid has a surface tension of 0.072 N/m. If a force of 0.036 N acts along a liquid surface, calculate the length of the surface over which the force acts.

Given:

γ = 0.072 N/m

F = 0.036 N

Using:

F = γL

Rearranging:

L = F / γ

L = 0.036 / 0.072 = 0.5 m

The length of the liquid surface is therefore 0.5 m.

What are the Factors affecting Surface Tension?

Surface tension is affected by temperature and substances dissolved in the liquid. Increasing temperature generally decreases surface tension, while substances such as soap can reduce it.

Why is Surface Tension important in Fluid Mechanics?

Surface tension is important in droplets, bubbles, capillary action, and interactions between liquids and solid surfaces.

What is an Important Fact about Surface Tension?

Surface tension is mainly caused by cohesion, the attraction between molecules of the same substance.