Learning Outcomes

1. State what soap is2. State what detergent is3. Describe soap preparation process4. Describe detergent preparation

process5. Describe the cleansing action of

soap6. Describe the cleansing action of

detergent7. Compare and contrast the

effectiveness of cleansing action of soap and detergent

8. Identify the additives in detergent and their respective functions

What is soap?Soaps are sodium or potassium

salts of long-chain fatty acids.

General formula of a soap can be written as:

RCOONa+ or RCOOK+

R is an alkyl group that usually containing 12 to 18 carbon atoms.

It can be saturated or unsaturated

SaponificationSaponification is a process to

prepare soap.Soap is made by boiling a mixture

of fats or vegetable oil with concentrated alkali (NaOH or KOH)

What is detergent?Detergent is non-soap cleansing

agent.

It is divided into natural detergent and synthetic detergent

Detergent is the sodium salt of sulphonic acid

Natural detergent is made from animal or vegetable oil while synthetic detergent is normally made from petroleum

Commercialized detergent are usually sodium alkyl sulphate and sodium alkyl benzene sulphonate

Cleansing Action of Soap and Detergent

Aim : To compare and contrast the effectiveness of

cleaning action of soap & detergentApparatus : 250cm3 beakers, 100cm3 measuring

cylinder, glass rodMaterial : Detergent & soap solution, soft water, hard water ( distilled water + MgSO4 ), pieces of cloth (2cm x 2cm) with oily stain

Procedures:1. Prepare 4 beakers with the content below:

2. Stir the solution in each beaker using a glass rod until no changes can be observed

3. Record all changes that occurred4. Place a piece of cloth with oily stain into each

beaker.5. Wash the oily stain on each piece using the

solution in each beaker and stirred6. Observe and record whether the oily stain on each

piece of cloth dissapear.

Experiment Content

I 100cm3 of soap solution

II 50cm3 of soap solution + 50cm3 MgSO4

III 100cm3 of detergent solution

IV 50cm3 of detergent solution + 50cm3 MgSO4

Result:

Conclusion: Soap solution was an effective cleansing

agent in soft water but not in hard water. Detergent solution was effective in both solution.

Experiment Observation

I A lot of lather was formed. The oily stain was removed. The cloth was clean

II No lather but white precipitate was formed. The oily stain remained on the cloth.

III A lot of lather was formed. The oily stain was removed. The cloth was clean

IV A lot of lather was formed. The oily stain was removed. The cloth was clean

Cleansing Action of Soap and Detergent

1. Soap reduces the surface tension of water.2. This increase the wetting ability of water.3. So, the surface of cloth is wetted thoroughly.

1. The hydrophobic part of the soap anion dissolves in the grease.

2. The hydrophilic part attracted to the water molecules.

1. Scrubbing helps pull the grease free from cloth surface.

1. Grease is removed from the cloth surface as tiny oil droplets.

2. Tiny oil droplets with negative charge repel each other.

3. This prevent them from redeposit on the surface.

Comparison of Soap and Detergent

Soap Detergent

StrengthBiodegradableNot poisonous to aquatic life

effective in hard water and acidic water

Weakness Not effective in hard water and acidic water

not biodegradable

Additives in detergent

Additives FunctionBiological enzymes To remove protein stains such as

blood

Fragrances To add fragrance to both the detergent and fabrics

Whitening agents To convert stains into colourless substances

Suspension agents To prevent the dirt particles removed from redepositing onto cleaned fabrics

Foam control agents

To control foaming in detergent

Builder To enhance the cleaning efficiency of detergent by softening the water