Soaps and detergents are typically considered by many to be the same, due to both being surfactants which are also washing compounds. However, they are very different as soaps are made of natural material while detergents are more synthetic. The effects of soap as a washing compound is negatively affected when they react with minerals in water (especially hard water), while detergents are less affected by minerals in water. Nonetheless, soaps are said to be more health and environmental-friendly as compared to detergent.
Despite the differences between soaps and detergents, their general cleansing action process is similar. This post, Part 3 in the series of short notes on Chemicals for Consumers by Berry Berry Easy for SPM Chemistry Form 5 students is about the cleansing action processes of soaps and detergents. Read all about this important sub-chapter and try to understand it.
[Tips: One of the obvious tips to assist student who suddenly forget which is soap and which is detergent, is simply to remember that you use soap while showering and detergent to wash clothes. Hence, you can easily link that soap are natural and detergent are synthetically manufactured.]
SPM Chemistry Form 5 Notes – Chemicals for Consumers (Part 3)
Cleansing action of soap and detergent
- Soap and detergent are surfactants. Surfactants are organic compounds that lower the surface tension of a liquid.
- Surfactants act as emulsifiers and foaming agents.
- Anion soap consists of carboxylate ion (hydrophilic = soluble in water) and long hydrocarbon tail (hydrophobic = soluble in grease /oils).
- Anion detergent consists of sulphate ion / sulphonate ion (hydrophilic = soluable in water) and long hydrocarbon tail (hydrophobic = soluble in grease / oils).
The action process
- Soap or detergent is added to water.
- This has lower the surface tension of water and increases the wetting ability of water.
- Hydrophilic part of the anion dissolves in water.
- Hydrophobic part dissolves in grease.
- Scrubbing helps to pull the grease free and break the grease into small droplets.
- These droplets do not coagulate and redeposit on the surface of the cloth. It is because the repulsion between negative charges on the surface.
- The droplets are suspended in water forming an emulsion.
- Foam produces to float the emulsion.
- Rinsing helps to remove these droplets.
This is the end of this notes. In the next part, Part 4 of notes on Chemicals for Consumers for SPM Form 5 Chemistry by Berry Berry Easy is about the effectiveness of the cleansing action of soap and detergent and additives in detergent. Do check back for the latest essential notes.