Soap has a unique ability to disrupt the hydrogen bonds between water molecules, which is largely due to its chemical structure. Soap molecules are made up of long hydrocarbon chains that are hydrophobic (water-repelling) and a polar head that is hydrophilic (water-attracting).
When soap is added to water, the hydrophilic heads of the soap molecules interact with the water, while the hydrophobic tails avoid the water. This interaction causes the soap molecules to arrange themselves in such a way that the hydrophilic heads face the water, and the hydrophobic tails point away from it. This forms structures known as micelles.
As these micelles form, they effectively reduce the number of hydrogen bonds that can occur between water molecules. Normally, water molecules are attracted to one another through hydrogen bonds, creating a cohesive structure. However, when soap is present, the soap molecules interfere with this cohesion by inserting themselves between water molecules, thus breaking some of those hydrogen bonds.
This reduced hydrogen bonding results in a decrease in water’s surface tension, allowing the water to spread and penetrate more effectively into surfaces and materials. This is why soap is such an effective cleaning agent; it not only helps water to spread, but it also helps to lift and wash away dirt and grease, which also disrupts interactions with other substances.