Grease and oil are hydrophobic substances, which means they repel water and do not dissolve in it. Cotton is a hydrophilic material, meaning it has an affinity for water, but it cannot easily remove grease and oil stains on its own due to the difference in their properties.
When you add detergents, such as soap, to water, they act as surfactants. Surfactants have molecules with both hydrophilic (water-loving) and hydrophobic (water-repellent) parts. This unique structure allows them to interact with both water and grease/oil simultaneously.
Here's how the process works:
Surfactant molecules surround and encapsulate the grease and oil stains on the cotton fabric with their hydrophobic tails facing inward, trapping the grease and oil within micelles.
The hydrophilic heads of the surfactant molecules face outward and interact with the water, creating a suspension of the grease and oil within the water.
Agitation, such as washing or scrubbing, helps to break up the grease and oil particles further and lift them from the cotton fabric.
The suspended grease and oil particles are then rinsed away with the water, leaving the cotton fabric clean.
In summary, adding detergents to water enhances the ability to remove grease and oil stains from cotton clothes by allowing the water to interact with these substances effectively, thanks to the surfactant's dual nature.