the effectiveness of the cleansing action of soap and detergent

Advantages of soaps
1. Soaps are effective cleansing agents in soft water, that is water does not contain
Mg2+ and Ca2+ ions.


2. Soaps do not cause pollution problems to the environment. This is because soaps
are made from chemical found in animals and plants. This means that soaps are
biodegradable, that is they can be composed by the action of bacteria.


Disadvantages of soaps
1. Soaps are ineffective in hard water, that is, water that contains magnesium and
calcium salts.


2. In hard water, soaps will react with Mg2+ and thus, soaps do not lather in hard
water.


3. Scum is grey solid that is insoluble in water. It consists of magnesium stearate and
calcium stearate.


4. Soaps are not also effective in acidic water, for example rainwater containing
dissolves acids. H+ ions from acids will react with soap ions to produce carboxylic
acids molecular size that are insoluble in water.


5. Stearic acids and other carboxylic acids do not act as cleansing agents because
they exist mainly as molecules and do not anionic hydrophilic ends (’head’) that
dissolves in water.


Advantages of detergents
1. Detergents are cleansing agents that are effective in soft water as well as hard
water. This is because detergents do not form scum with Mg+ and Ca2+ ions found
in hard water.


2. The detergents ions (R –O – SO3- and R – SO3- ) react with Mg+ and Ca2+ ions in hard
water. However, the magnesium salts and calcium salts which are formed are
soluble in water. Hence, the scum is not formed and the detergents are still active
in hard water and lathers easily.


3. Detergents are synthetic cleansing agents. This means that the structure of the
hydrocarbon chain can be modified to produce detergents with specific properties.
Nowadays, different types of detergents have been synthesised for specific uses
such as shampoos and dish cleaner.


4. Furthermore, detergents are also effective in acidic water because H+ ion is acidic
water do not combined with detergents ions.


Disadvantages of detergents
1. Most detergents have branched hydrocarbon chains and are non-biodegradable,
that is, they cannot decomposed by bacteria. As a result, non-biodegradable
detergents cause water pollution.


2. Phosphates in detergents act as fertilizers and promote the growth of water plants
and algae. When the plants die and decay, they will used up the oxygen dissolves
in water. This will decrease the oxygen content in water and kill fishes and other
aquatic lives.


3. Detergents produce a lot of foam in water. The layer of foam that covers the water
surface will prevents oxygen from dissolving in water. This condition will cause
fish and other aquatic life ti die from oxygen starvation.


4. Additives such as sodium hydrochlorite (bleaching agents) releases chlorine gas
in water that is acidic. Chlorine gas is highly toxic and kills aquatic life.

                                                                ~ detergent~