Soap is effective at removing oil and grease from dishes due to its unique molecular structure and properties. Oil and water do not mix well because of their different polarities: oil is non-polar, while water is polar. This characteristic makes it challenging for water alone to dissolve or remove oils from surfaces.
However, soap is an emulsifier, which means it has both polar and non-polar properties. One end of the soap molecule is attracted to water (hydrophilic), while the other end is attracted to oils and grease (hydrophobic). When you mix soap with water, it forms micelles—tiny clusters of soap molecules—where the hydrophobic ends of the soap molecules surround the oil or grease particles, while the hydrophilic ends remain in the water.
The process works as follows:
Breaking down oil: The hydrophobic tails of the soap molecules surround and encapsulate the oil or grease droplets, breaking them down into smaller, dispersed particles.
Suspension: The now dispersed oil and grease particles are held in suspension within the soapy water, preventing them from reattaching to the dishes.
Rinsing away: When you rinse the dishes with clean water, the soapy water carrying the suspended oil and grease particles is washed away, leaving the dishes clean.
In contrast, when you try to wash oil or grease off with just water, the non-polar nature of the oil prevents it from dissolving in the polar water. The oil tends to stick to the dish's surface, making it difficult to remove without the aid of soap.
In summary, soap's ability to act as an emulsifier allows it to break down and suspend oil and grease in water, making it much more effective at removing these substances from dishes compared to using water alone.