What happens to the surface tension of water when soap is added?

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Question: What happens to the surface tension of water when soap is added?

Options:

Correct Answer: Decreases

Solution:

Adding soap to water decreases its surface tension because soap molecules disrupt the cohesive forces between water molecules.

What happens to the surface tension of water when soap is added?

What happens to the surface tension of water when soap is added?

Step 1: Understand what surface tension is. Surface tension is the force that makes the surface of water behave like a stretched elastic sheet.
Step 2: Know that water molecules are attracted to each other. This attraction creates strong cohesive forces at the surface.
Step 3: When soap is added to water, soap molecules mix with the water.
Step 4: Soap molecules have a special structure that disrupts the attraction between water molecules.
Step 5: Because the soap molecules interfere with the water molecules, the cohesive forces are weakened.
Step 6: As a result, the surface tension of the water decreases.

Surface Tension – The cohesive forces between liquid molecules at the surface that create a 'skin' effect.
Effect of Surfactants – How substances like soap, which are surfactants, alter the properties of water.