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4541 CHEMISTRY Chapter 14

Chapter 14 : CHEMICALS FOR CONSUMERS

5.1 CLEANING AGENT [SOAP AND DETERGENT]

5.1.1 SOAP

(a) Soaps are sodium or potassium salt of long chain fatty acids*. Fatty acids* organic acid with long carbon chain ; CnH2n+1COOH ; n 10.

Example of soap :

Type of soap FormulaSodium laurate CH3 (CH2)10 COONaSodium palmitate CH3 (CH2)14 COONaPotassium stearate CH3 (CH2)16 COOKPotassium oleate CH3 (CH2)m CH=CH(CH2)n COOK

(b) Soap Preparation Process

(i) Soap can be made from animal fats or vegetable oils. Animal fats commonly used are from cows and goats

while vegetable oils often used are palm oil, olive oil and coconut oil.

(ii) Soap are prepared by hydrolysing fats/oils in potassium hydroxide or sodium hydroxide solution [hydrolysing fats or oils under alkaline condition], the reaction is called saponification.

(iii) The saponification process involves boiling fats/oil with concentrated sodium hydroxide solution or potassium hydroxide solution. The products are glyserol and the salts of fatty acids which are soaps.

General equation :

or

H O H O

H C O C R H C O H R C O Na

O O

H C O C R’ + 3NaOH H C O H + R’ C O Na

O O

H C O C R” H C O H R” C O Na

H H Fat/oil sodium hydroxide glycerol salt of fatty acid

R, R’ and R” are long hydrocarbon chain (alkyl group). R, R’ and R” can be from the same or different groups.

Chapter 5 Chemicals for Consumers1

-

-

-

+

+

+

Fats/oil(ester)

Sodium hydroxide (alkali)

Sodium salt of fatty acid (soap)

Glycerol (alcohol)+ +


(c) The general formula of soap is : or

where R is alkyl groupExample of soap :

Oil/fat used Fatty Acid Soap

Coconut oilC11H23COOHLauric acid

C11H23 COONaSodium laurate

Palm oilC15H31COOHPalmitic acid

C15H31 COOKPotassium palmitate

Animal fatsC17H34COOHStearic acid

C17H34 COONaSodium stearate

Activity 1 :-

1 Soap can be produced by using ……………………and ………………………...

2 When soap is dissolved in water, it reduces the…………………………...of water.

3 Soap cannot be used in hard water which contains of the………….. ions and………… ions.

4 Soap is a common cleaning agent in daily life.

(a) Name the process of the production of soap.

…………………………………………………………………………………………

(b) State two common materials used to prepare soap.

…………………………………………………………………………………………

(c) State two medium where soap cannot clean effectively.

…………………………………………………………………………………………

(d) State one property of soap.

…………………………………………………………………………………………


RCOO- Na+ RCOO- K+


Activity 2 :-

1 Diagram below shows the set-up of apparatus to prepare soap.

(a) Name the process of preparing soap.

…………………………………………………………………………….

(b) Name the solution P.

…………………………………………………………………………….

(c) State the purpose of adding sodium chloride to the reaction mixture in the experiment.

……………………………………………………………………………………………

……………………………………………………………………………………………

(d) Diagram below shows the structure of a soap ion.

Based on the diagram, which part is soluble in the water and grease?

Water : ………………………………………………………………

Grease : ……………………………………………………………..


Heat

Palm oil +

Solution P

Distilled water +

Sodium chloride

Mixture

SoapCool

CH 2

CH3

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2 CH2

C - O- || O

Part X Part Y


5.1.2 DETERGENT

(a) Detergent is cleaning agent that is not soap. Any cleaning agent that is not soap is a detergent.

(b) The different between soap and detergent is their raw material used. Soap from animal fats or vegetable oils Detergent from synthetic resources such as petroleum

(c) Detergents are sodium salts of alkylbenzene sulphonic acid or alkyl sulphonic acid.

(d) Two common groups of detergent are :

(i) Sodium alkylbenzene sulphonate (sodium salt of alkylbenzene sulphonic acid)

O

R-O- -S-O-Na+

O

(ii) Sodium alkyl sulphonate (sodium salt of alkyl sulphonic acid)

O R-O-S-O-Na+

O Where R represents a long chain hydrocarbon.

(e) Detergents are made from hydrocarbon obtained from petroleum.

(f) Preparation of detergent.

(i) Preparation of sodium alkyl benzene sulphonate

Alkylation of alkene Long chain alkene of petroleum react with benzene to form alkyl benzene.

Sulphonation of alkylbenzene The Alkylbenzene is then reacted with concentrated sulphuric acid to form

alkylbenzene sulphonic acid .

Neutralisation The alkylbenzene sulphonic acid is then converted to sodium alkylbenzene

sulphonate salt by the reaction with sodium hydroxide solution.



(ii) Preparation of Sodium alkyl sulphonate Hydration of long chain alkene

A long chain alkenes (product of petroleum) are hydrated by steam to form a long chain alcohol.

Sulphonation of alcohol The long chain alcohol is then reacted with concentrated sulphuric acid to form

alkyl sulphonic acid.

Neutralisation The alkyl sulphonic acid is then neutralised sodium hydroxide solution to produce

sodium alkyl sulphonate, which is salt.



5.1.3 THE CLEANSING ACTION OF SOAP AND DETERGENT

(a) The cleansing action of soap :

1. A soap with the general formula RCOO - Na + / RCOO - K + is ionises in water to produce sodium/potassium cation, Na+ (or K+) and soap ion/anion, RCOO-

2. A soap anion is made up of two parts :

O

R – C – O

Alkyl Carboxysilate ion

R (alkyl) is a long hydrocarbon chain which are : Hydrophobic (repelled by water) Non-polar end (no charge) Soluble in oil or grease.

–COO- is a carboxylate ion which are : Hydrophilic (soluble in water) Polar end (Negatively charged) Insoluble in oil or grease.

3. Example : Sodium laurate : CH3 – (CH2)10 – COONa

Simplified representation of soap anion is :

4. The hydrophobic and hydrophilic parts of soap anions work together to remove greasy stains :

The soaps ionises in water to produce free moving soap anions and cations. Soap reduces the surface tension of water which will increase wetting ability of

water. Therefore, water wets the dirty cloth. The hydrophilic part of the soap ion / anions remains in water while the

hydrophobic part dissolve and penetrate into the grease.


-

CH3

CH2

CH2

CH2 CH2

CH2 CH2

CH2 CH2

CH2 CH2

COO- Na+

Hydrocarbon chain / hydrophobic Caboxylate ion / hydrophilic

Hydrophobic Hydrophilic

Hydrophobic partHydrophilic part

water

grease

Cloth


By the movement of water during scrubbing and rubbing, grease is loosened and lifted off the surface.

The hydrophobic of soap anions surround the grease, the grease is suspended in the water. The grease is dispersed into smaller droplets The small droplets do not redeposit on the surface of the cloth due to repulsion between

negative charges on their surface. The droplets are suspended in water, forming an emulsion. Rinsing away the dirty water removes the grease droplets and the surface of the cloth is then

clean.

(b) The cleansing action of Detergent


Small droplet of grease


Detergent dissolves in water to form detergent ion / anion and sodium ion / cation.For example the ionisation of sodium alkyl sulphate.

O R-O-S-O-Na →

O

The structure of a detergent anion is similar to a soap anion. The detergent anion also made up of two parts hydrophobic part and hydrophilic part.

Alkyl suphate ion :

O R-O-S-O-

O

Alkylbenzene sulphonate ion :

O

R-O- -S-O-

O

The cleansing action of detergent is also very similar to soap, the hydrocarbon chain dissolve and penetrate in grease while the sulphate ion group remain in water.

Activity 3 :-


hydrophobic hydrophilic


Draw diagrams to show the cleansing action of soap or detergent :

1. When soap or detergent is added into the water, it dissolved to form hydrophobic part and hydrophilic part.

2. Hydrophobic part is soluble in the grease and hydrophilic part is soluble in water.

3. Soap anion can reduces the surface tension of the water.

Mechanical agitation or heating during scrubbing helps to pull the grease free and break the grease into small droplet.

4. The droplet do not coagulate and redeposite on the surface of cloth due to the repulsion between the negative charges of their surface.

These droplets are suspended in the water forming an emulsion.

Rinsing washes away these droplets and leaves the surface clean.

5.1.4 THE EFFECTIVENESS CLEANSING ACTION OF SOAP AND DETERGENT

(a) The effectiveness of soap is reduced when used in hard water.



(b) Hard water contains high concentration of calcium ion, Ca2+ and magnesium ion, Mg2+.(c) These ions react with soap anions to form scum . [ Insoluble salt / a precipitate ]

2C17H35COO - (aq) + Mg2+(aq) (C17H35COO)2Mg (s) ↓Stearic anion/soap anion Insoluble magnesium stearate (scum)

2C17H35COO - (aq) + Ca2+ (C17H35COO)2Ca (s) ↓Stearic anion/soap anion Insoluble calcium stearate (scum)

(d) Formation of scum reduces the amount of soap available for cleaning.(e) Detergent anions do not form scum with calcium ions and magnesium ions.

This means detergent can act as cleaning agent in hard water. Thus, detergent is more effective than soap in hard water.

Cleaning Agent Soft water Hard water

Does not form scum Forms scum

Does not form scum Does not form scum

(f) Detergents generally contain a wide variety of additives. Additives are added to enhance its cleaning efficiency.

Additive FunctionBiological enzyme such as lipase, proteases, cellulases and peptidase

Remove protein stains such as blood

Whitening agent such as sodium perborate and sodium hypochlorite

Convert stain into colourless substances

Optical whitener To add brightness and whiteness to white fabric

Builder such as sodium tripolyphosphateTo enhance the cleaning efficiency of detergent by softening the water

Suspension agent such as carboxymethylcellulose

To prevent the dirt particles remove from redepositing on to cleaned fabric

Filler such as sodium sulphate, sodium silicate

To add to the bulk of the detergent and enable it to be poured easily

Foam control agent such as silicones To control foaming in detergent

Fragrances Add fragrance to both fabrics and detergent

Activity 4 :-

1 Detergent is a type of sodium salt that can be used as cleaning agent.

(a) Name three materials used to prepare detergent.

………………………………………………………………………………………………

(b) Name an example of detergent.

………………………………………………………………………………………………



(c) What is the advantage of using detergent as a cleaning agent?

………………………………………………………………………………………………

(d) What is the disadvantage of using detergent as a cleaning agent.

………………………………………………………………………………………………

2 Soap cannot clean effectively in hard water but detergent can.

(a) What is hard water?

………………………………………………………………………………………………

(b) What happens when a little of soap is shaken with hard water?

………………………………………………………………………………………………

(c) With the exception of hard water, name another medium that is not suitable to be used with soap?

………………………………………………………………………………………………

(d) Explain why detergent can be used in hard water.

………………………………………………………………………………………………

………………………………………………………………………………………………

………………………………………………………………………………………………

3 Additives in detergent increase the effectiveness of detergent as a cleaning agent.

(a) Name the additive that keeps the detergent powder dry.

………………………………………………………………………………………………

(b) Name the additive that removes organic stain.

………………………………………………………………………………………………

(c) Name the additive that prevents the fading of colour

………………………………………………………………………………………………

(d) Name the additive that reduces the formation of foam.

………………………………………………………………………………………………

Activity 5 :-

1 Complete the following table to compare and contrast between soap and detergent.



Cleaning agent Soap Detergent

Sources

General formula

The structure of polar end

(Hydrophilic)

Effectiveness

Formation of scum

Formation of precipitate

pH

Effect on environment

2 Diagram below shows the structural formulae of two cleaning agents.

(a) Compare the effectiveness of cleaning agent X and cleaning agent Y as cleansing agent.

(b) Describe an experiment in laboratory to prepare a sample of soap from palm oil.

5.2 FOOD ADDITIVES

1. Food additives are added to food to :

Improve its appearance, taste or texture.



Preserve the food.

2. Food additive can be natural substances or synthetic compounds.

3. Food additives are classified according to their function.

Type of food additive Example Food Function / How it work?

Preservative

Sodium nitrateSausage, burger, luncheon meat. Prevent food from being

spoil Prevent or slow down

the growth of microorganisms

Sulphur dioxideFruit juice, jam, soft

drink.

Sodium benzoateChilli and tomato

sauce, oyster sauce, fruit juice

Salt Salted fish Prevent food from being

spoil Remove water from the

cell of microorganism and retards the growth of microorganism

Sugar Jam

Vinegar Pickled

Prevent food from being spoil

Provide acidic condition that inhibit the growth of microorganism.

AntioxidantAscorbic acid (vitamin C),citric acid

Cake, biscuit, margarine, fruit juice

Prevent oxidation that causes rancid fats and brown fruits.

Flavouring agent

Monosodium glutamate (MSG)

Soup, frozen food, meat and fish based

product

Enhance the natural flavour of the food.

Synthetic essences (ester) :Ethyl butanoate

Cake, jam, ice cream Produce artificial flavour Improve the taste/flavour

Aspartame,Sucrose

Drink and juice, frozen dessert.

Sweeten the food, it has less calories than sugar.

Sucrose To give flavour To improve the taste As a sweetener



Thickening agentAcacia gum

Ice cream, jelly, chewing gum.

Improve the consistency of food by giving a firmer, more uniform and smoother.

Agar or pectin, Gelatin

Jam

Stabilisers LecithinChocolate, ice

cream, butter, salad dressing

Improves the texture of food by preventing an emulsion* from separating out into a layer of water and oil.

* emulsions are either oil droplets suspended in water or water droplets suspended in oil.

Colouring

Azo compound(tartrazine)

Orange juice, jamAdd or restore the colour in a food to make the food appearance look more attractive.

Triphenyl compound

(brilliant blue FCF)

Sweets, cake

Activity 6 :-

1 Salt is an example of natural preservative.

(a) What is preservative?

………………………………………………………………………………………………

(b) How does salt function as preservative?

………………………………………………………………………………………………

(c) State another example of natural preservative.

………………………………………………………………………………………………

(d) Name an artificial preservative.

………………………………………………………………………………………………

2 Ester is an example of flavouring.

(a) Name the substances used to prepare ester.

………………………………………………………………………………………………

(b) Name an ester that has apple flavour.

………………………………………………………………………………………………



(c) Name the substances used to prepare the ester named above.

Ester Substances Flavour

(d) State another example of flavouring.

………………………………………………………………………………………………

3 Food additives are used to enhance the quality of food.For the following question, name the type of food additive that shows a particular function.

(a) Prevent foods from being oxidised.

………………………………………………………………………………………………

(b) Enhance the taste of the food.

………………………………………………………………………………………………

(c) Keep food to last longer.

………………………………………………………………………………………………

(d) Improved the texture of food.

………………………………………………………………………………………………

4 Octyl ethanoate, pectin, tartrazine and benzoic acid are some of the food additives found in the sample of jam.

(a) Name the preservative used.

………………………………………………………………………………………………

(b) What is the function of pectin?

………………………………………………………………………………………………

(c) What is the colour of jam?

………………………………………………………………………………………………

(d) What is the colour of the jam?

………………………………………………………………………………………………

5 Aspartame is a type of ………………………that can be used to replace ………………………Activity 7 :-



Diagram below shows a part of the label of a tin of sardines

List all the food additives used in the sardines and their uses.

2 Diagram below shows a list of a type of food.

From the list of ingredients, select two substances used as food addatives.State the function of each food addative that you have selected.

5.3 MEDICINE


Sardines in Tomato Sauce

Ingredients :Sardines, tomato sauce, refined palm oil, salt, xanthan gum and dye A

PINEAPPLE JELLY

Ethyl butanoate

Sucrose

Citric acid

Gelatin

Sodium benzoate


1. A medicine is used to prevent or cure disease or to relieve pain.

2. Medicines can be classified to :

(i) Traditional medicine. Obtained from natural sources (plants or animals), without chemical reactions. Prepared by boiling parts of the plants or crushed to make a paste. Usually not processed.

(ii) Modern medicine. Chemicals that are extracted from plants and animals or synthetic chemicals. It is manufactured in the form of liquid, capsules, powders and tablet. Usually processed in the laboratory.

5.3.1 Traditional medicine : Complete the following table for some common traditional medicines and their functions :

Traditional medicine Function

Aloe vera (lidah buaya)

Bitter gourd (peria)

Ginger (halia)

Garlic (bawang putih)

Hibiscus (bunga raya)

Turmeric (kunyit)

Tamarind (asam jawa)

Hydrscotyle asiatica (pegaga)

5.3.2 Modern medicine



Classification of modern medicines according to their effects on the body.

Type of modern medicine

Function Example Note

AnalgesicsRelieve pain without causing unconsciousness

Aspirin ( acetylsalicylic

acid)

Relieves pain caused by headache, toothache and arthritis.

Reduces fever and inflammation caused by infection.

Causes internal bleeding ulceration (not suitable for gastric patients).

Paracetamol Relieves pain and reduces fever Does not reduces inflammation Does not irritate the stomach

CodeineC18H21NO3H2O

Cough medicine. Causes sleepiness. Misuse of codeine causes

addiction.

Antibiotic

Used to treat infections caused by bacteria or fungi.Antibiotics kill or slow down the growth of bacteria or fungi

Penicillin Patient must take full course of

the antibiotic prescribed by the doctor to make sure all the bacteria are killed, otherwise the bacteria may become resistant/imune to the antibiotic.

Side effect of antibiotics are headache, allergic reaction and dizziness.

Streptomycin

PsychotherapeuticUsed to treat mental illness

Stimulant : amphetamine

To reduce fatigue and elevate mood.

Can cause addiction

Antidepressant :Barbiturates and

tranquilizer

To reduce tension and anxiety Can cause addiction

Antipsychotic : chloropromazine

To treat psychiatric illness with severe mental disorder.

Activity 8 :-



1 Complete table below to differentiate between traditional medicines and modern medicines.

Traditional medicines Modern medicines

Usually not processed.Usually …………… in laboratories.

Derived from …………….. or

……………...

Synthesized based on substances found in nature.

2 Aspirin is an example of analgesic.

(a) What is an analgesic?

………………………………………………………………………………………………

(b) Explain why patient should take plenty of water with aspirin.

………………………………………………………………………………………………

………………………………………………………………………………………………

3 Penicillin and streptomycin are the examples of antibiotics.

(a) What is the function of an antibiotic?

………………………………………………………………………………………………

(b) Why are penicillin and streptomycin given by injection and not taken orally?

………………………………………………………………………………………………

4 Psychotherapeutic medicines can be classified into stimulant, antidepressant and antipsychotic.

Type of Psychotherapeutic

Function Example Side effect

stimulant

antidepressant

antipsychotic

5 Diagram below shows a conversation between Aisyah and Zulkifli.



These two students met a doctor and some medicine were prescribed to them. For each medicine, state its name, type and the correct usage.

Student Name of medicine Type of medicine Correct usage

Aisyah

Zulkifli

END OF CHAPTER 5


I have a headache. The doctor advised me to take this medicine and follow his prescription.

I have a bacterial infection. The doctor advised me to follow his prescription strictly.

Aisyah Zulkifli

c14_notes(s) chemical consumer

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