What is soap?

wateroilsoap moleculeIf oil is added to water, the two liquids do not mix.Because of this, grease stains can be difficult to remove during washing.Soaps are compounds which act as emulsifiers.This means that they help the oil to mix with the water.

How do soaps work?

How are soaps made?

Soaps are usually made from vegetable fats and oils. These consist of 3 fatty acid chains, held together by a glycerol molecule.The reaction used to make soap from fats and oils is called saponification.

How are soaps made?

What are soapless detergents?

Soapless detergents can be made from crude oil, rather than vegetable oils or animal fats.sodium octadecylsulfonatehydrophobic end interacts with oil moleculeshydrophilic end interacts with water moleculesSoapless detergents are still made of long, hydrophobic carbon chains, but the hydrophilic end of the molecule is a sulfonate:

Soaps vs. soapless detergents

What are the advantages and disadvantages of soapless detergents over soaps?Soaps form a scum with hard water, meaning that it is more difficult to produce a lather. Soapless detergents react with the substances in hard water to form soluble compounds, and so do not form a scum.

Soapless detergents can be made from the by-products of the oil refining process, so can be cheaper to produce than soaps.

Some soapless detergents are not biodegradable. This means that they stay in the water system causing froth in rivers and streams.

Teacher notesAsk students to decide which statements are advantages or disadvantages of soaps and soapless detergents.

Biological and non-biological detergents

Biological detergents are soapless detergents that contain enzymes.The enzymes are used to break down chemicals, e.g. in stains on clothes.Non-biological detergents do not contain enzymes, but just rely on the action of the detergent to remove grease and stains from items.

Photo credit: 2009 Jupiterimages Corporation

Advantage or disadvantage?

Teacher notesAsk students to decide which statements are advantages or disadvantages of soaps and soapless detergents.Photo credit: 2009 Jupiterimages Corporation