Give the Definition of Soap and Some Examples of Soap

Soap and detergent

·  Give the definition of soap and some examples of soap

·  Salt that are formed by neutralization between a fatty acid and an

alkali.

·  One example of soap is sodium palmitate, CH₃(CH₂)₁₄COONa. It is

formed when palmatic acid is neutralized by sodium hydroxide, NaOH.

CH₃(CH₂)₁₄COOH(aq) + NaOH(aq) → CH₃(CH₂)₁₄COONa(aq) +H₂O(l)

·  Briefly explain the history of the soap manufacturing in a flowchart.

·  In the past, soap was made by mixing animal fats with alkaline and wood ashes

·  Large-scale commercial soapmaking occurred in 1791 when a French Chemist, Nicholas Leblanc patented a process for making soda ash or sodium carbonate from common salt. The process yielded large quantities of quality soda ash.

·  Soap can be prepared through saponification. Use a flow chart to show soap preparation process in the laboratory, starting with the raw materials. Include any relevant chemical equation.

Ø  Oils and fats are esters formed from glycerol and fatty acids.

Ø  It made up through heating oils or fats with an alkali such as sodium hydroxide, NaOH.

Ø  The oil or fat molecules are “broken up” or hydrolyzed to glyce ro l and fatty acids.

Ø  This reaction is the reverse of esterification (saponication)

Ø  The fatty acids formed then react with sodium hydroxide, NaOH to form a salt (soap)

Saponification of oils or fats

·  Fats and oils are hydrolyzed (split) with a high-pressure steam to yield crude fatty acids and glycerol.

·  The fatty acids are then purified by distillation and neutralized with an alkali to produce soap and water (neat soap-soap in liquid form).

·  Fatty acid + NaOH → Glycerol + Sodium soap

Ø  Sodium soaps are "hard" soaps.

Ø  The more saturated the oil (tropical vegetable oils such as coconut oil), the harder the soap.

·  Fatty acid + KOH → Glycerol + Potassium soap

Ø  Potassium soaps are softer and are found in some liquid hand soaps and shaving creams.

·  Give the definition of detergent and some examples of detergents.

·  Salt that are formed by neutralizing an alkyl hydrogen sulphate with an alkali.

·  One example of detergent is sodium lauryl sulphate

·  Detergents may contain many other substances in addition to the substances that does the cleaning and also to make it more effective.

·  These substances are called additives

·  Use a flow chart to summarize the steps in the preparation of detergent. Include any relevant chemical equation.

A synthetic detergent, a sodium alkyl sulfate called sodium dodecylsulfate, will be prepared by reacting dodecyl alcohol (dodecanol) with sulfuric acid.

Dodecanol Sulfuric acid Dodecylsulfate

The resulting dodecylsulfate is converted to the sodium salt by a reaction with sodium hydroxide.

Dodecylsulfate sodium dodecylsulfate

·  Both soap and detergent clean so much better than water alone. Use a flow chart and colourful diagram to summarize the cleansing action of soap and detergent.

·  One part of the soap and detergent anion is negatively charged (polar end).
- It dissolves in water. It is hydrophilic or “likes water”.

·  The other part has no charge (non-polar end)

-  It dissolves in oil or grease. It is hydrophobic or “hates water”.

·  These two parts work together to remove grease.

v  When soap or detergent is added to the dirty surface of a piece of cloth covered with a layer of oil or grease

(a)  The negatively charged ‘heads’ (hydrophilic) of soap ions or detergents ions dissolves

in water

(b)The hydrocarbon ‘tails’ (hydrophobic) of soap or detergent ions dissolves in the layer

of grease

v  If the water is agitated slightly, the grease begins to lifted off the surface.

v  When the cloth is rinsed with water, the droplets will be carried away

v  Heating and stirring may help to loosen the dirt particles from the material being washed

·  Compare and contrast the effectiveness of cleansing action of soap and detergent in hard water by using mind maps or table.

Hard water contains a great amount of calcium and magnesium ions. These ions react with the soap to form an insoluble precipitate known as soap scum.

Properties / Soap / Detergent
Cleaning power / Less powerfull / More powerfull
Ease of rinsing / It is difficult to wash away all soap on clothes. The soap that remains leave and odour and spoils the fabrics / Rinse out well from clothes
pH / Slightly alkaline / Can be controlled to suit the cleaning task
Molecular structure / Determined by the fatty acids found in the oil or fat used to produce soap / Can be modified to suit the cleaning task. For example, a detergent can be made specially for cleaning toilet bowls
Formation of scum / Form scum with hard water / Does not form scum with hard water

·  Detergent consists of various additives. What is the purpose of adding detergent additives? Construct a mind map to show the additives in detergent and their respective functions.

Addictives / Example / Function
Biological enzyme / Amylases, proteases, cellulases / To remove protein stains such as blood
Whitening agent / Sodium perborate / To convert stains into colourless substances
Optical whitener / Fluorescent dyes / To add brightness and whiteness to white fabrics
Builder / Sodium tripolyphosphate / To enhance the cleaning efficiency of detergent by softening the water
Suspension agent / carboxymethylcellulose / To prevent the dirt particles removed from redepositing onto cleaned fabrics.
Filler / Sodium sulphate, sodium silicate / To add to tha bulk of the detergents and enable it to be poured easily
Foam control agents / Silicones / To control foaming in detergent
Fragrance / - / To add fragrance to both detergent and fabrics