Question

How does detergent change surface tension?

Answer 1

Detergents are the potassium or sodium salts of a long alkyl chain ending with a sulfonate group. They are soluble in hard water. They contain surfactants.
Surfactants or surface active agents are the compounds that lower the surface tension between two liquids, between a gas and a liquid, or between a liquid and a solid. Surface tension is the tension of the surface film of a liquid caused by the attraction of the particles in the surface layer by liquid.

Complete step by step answer:
Surface tension is the tension of the surface film of a liquid caused by the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize surface area.
Have you seen that water drops do not stick to glass panes uniformly? This is because of surface tension $d/t$ their cohesive forces not letting them stick to the glass panes.
And same thing occurs in washing clothes. The water doenit net the clothes enough to clean the dirt.
This is the area where detergents and soaps are being used.
When you add detergent to water it reduces its surface tension. Which compound is responsible for this phenomenon. These are the surfactant or surface-active agents.
These surfactants reduce the surface tension of water and enhance its ability to stick to things.
Water sticks to the clothes and spread over a larger area than it usually could have.
In this way detergent has an effect on surface tension. They tend to reduce the surface tension.
Surfactants in detergents play a very important role .On one end, they attach themselves to the water molecules and on the other end, they attach themselves to the dirt present in unclean clothes. The surfactants help spread water, then they act on the grease by attaching themselves to it, and when this water is disposed of, it carries away all the dirt with it.

Note: This is why water alone will not help with cleaning action. The surfactants are very useful in this way that they are made of two ends, one which is attracted to water, hydrophilic, and attaches itself there, while the other is attracted to grease, oily substances, hydrophobic, and dirt and attaches itself there.