We know that water alone cannot perform these tasks. Pure water cannot make the black shirt return to white, miracuosly lift the stain from the carpet, and make the windows see through. This is becuase soap acts as what we call an emulsifier. This means that the soap makes oil and water mix, so that our household bacteria is instantly removed.
Detergents are mostly known as surfactants, which can easily and quickly be created from petrochemicals. Surfactants reduce the "surface tension" of water, meaning that on water's surface, the molecules are surrounded by other water molecules only onthe water side. This creates a tension becuase the water molecules get pulled into the body of water. This causes the water to create the drops we know.
However when cleaning, surface tension must be reduced so that the water can spread and create a wet apperance. (Unlike our chemistry tables)
This is where the surfactants come in. Their job is to mix into the water and lift up the soil, dirt, (or whatever your thing is) so that the water can rinse it away.
