Using concept of Surface Tension, explain why does the detergent cause the effect observed?
Surface tension is a property of liquids that causes them to minimize their surface area and form droplets or have a curved shape. It arises due to the attractive forces between the particles on the surface of the liquid. Detergent molecules have a unique structure that allows them to reduce surface tension.
Detergents are made up of molecules that have both hydrophilic (water-loving) and hydrophobic (water-repelling) ends. When detergent is added to water, these molecules orient themselves at the water-air interface. The hydrophobic tails of the detergent molecules are repelled by water and face towards the air, while the hydrophilic heads are attracted to water and stay in the aqueous phase.
When a detergent is introduced into a container filled with water, it starts to spread on the surface of the water. This is because the hydrophobic tails of the detergent molecules try to avoid contact with the water and move towards the air. This spreading action disrupts the cohesive forces between water molecules and reduces the surface tension.
As the detergent spreads on the water surface, it forms a thin layer that continues to lower the surface tension. The detergent molecules also start to surround other particles or impurities present in the water, such as dirt or oil droplets. By attaching to these impurities, the detergent molecules form small aggregates or micelles, effectively trapping the impurities within.
This mechanism allows detergents to clean surfaces effectively. The reduced surface tension and the ability of detergent molecules to surround and lift away dirt make it easier to remove dirt and stain particles from surfaces. The detergent molecules join together to form a layer around the dirt particles, effectively separating them from the surface.
In summary, detergents reduce the surface tension of water by disrupting cohesive forces between water molecules. This property enables detergents to spread, form micelles around impurities, and enhance the cleaning process.