CHEMICALS FOR CONSUMERS

NAME: THARANI A/P THIAGARAJANCLASS: 5 SIGMATEACHER: PUAN RUSMAINI

5.1 SOAPS AND DETERGENTS

1. Cleansing agents are chemicals subtances that remove grease and dirt.

TYPES OF CLEANSING

AGENTS

Soaps

Detergents

THE HISTORY OF SOAP MANUFACTURING

1.Soap have been used for more than 3000 years. It was recorded that theBabylonians were making soaps around 2800 B.C.2.In ancients time, soap made from ashes of plants which contain sodium carbonate and potassium carbonate. The ashes were boiled with lime (calcium oxide) to produce caustic potash (potassium hydroxide). Caustic potash is then boiled with the animal fats to produce soap.

a ) As h + L ime C aus t i c Po ta sh

 

b)Caustic Potash + Animal Fats Soap 4.In 1861, the Belgian Chemist Ernest Solvay (1838-1922) discovered the process to make soda (sodium carbonate) from common salt (sodium chloride) and calcium carbonate.5.This process is known as the Solvay Process which produces sodium carbonate cheaply for industrial use. Sodium carbonate (often called soda or soda ash) is used for making glass, soaps and detergents.6.Michel Chevreul (1786-1889), a French chemist, was noted for his research in the composition of animal fats is composed of fatty acids and glycerol. This discovery contributed to the rapid development of the soap and candle industry. 

PREPARATION OF SOAP BY SAPONIFICATION

1. Soap is a cleansing agents produced by the reaction between sodium hydroxide andpotassium hydroxide with animal fats or vegetable oils. This reaction is known as saponification.Some examples of soaps are shown below.

a) Sodium palmitate,

b)Sodium oleate,

c)Sodium stearate, Additives such as perfume, colouring matter and sometimes antiseptics are added tosoaps to enhance their marketability.

2. Fats and vegetable oils are large, naturally occurring ester molecules. When fats or oils are boiled with concentrated alkalis, such as sodium hydroxide, saponification occurs and the ester molecules are broken down into soap and glycerol.Fats or vegetable oils + concentrated alkalis soap +glycerol

3. Saponification is the alkaline hydrolysis of ester using alkali solutions. From the chemist aspect, soaps are sodium salts or potassium salts of long chain carboxylic acids (with 12 to 18 carbon atoms per molecule).

5. Glyceryl tristearates are naturally occurring esters commonly found in animal fats andvegetable oils. When the ester is boiled with concentrated sodium hydroxide solution,saponification (alkaline hydrolysis) occurs and mixture of sodium stearate (soap) and glycerol isobtained.

6.The soap produced can be precipitated by adding common salt (sodium chloride) to the reaction mixture which reduce the solubility of soap in water.

7. The properties of soap depend on :a) The type of alkali used for saponification b) The type of animal fats or vegetable oils used. 8. Soaps produced from sodium hydroxide are hard, whereas soaps produced frompotassium hydroxide are soft. 9. Animal fats (tallow) from cows and vegetable oils (such as palm oil or olive oil) aeused for making soap.

The structure of soap molecule1. When soap is dissolved in water, it will dissociate and produce sodium ions andcarboxylate ions ( ). For example, sodium stearate dissolves in water to form sodium ions and stearate ion.

  sodium stearate  stearate ions

2. The stearate ions take part in the removal of dirt but the sodium ions do not. The stearate ion consists of two parts: the ‘head’ and the tail. The head is negatively charged and the tail is a long hydrocarbon chain.

3. The head contains the -C-O- ions which dissolves readily in water (hydrophilic) butdoes not dissolve in oil. Conversely, the ‘tail’ contains a long hydrocarbon chainwhich is insoluble in water (hydrophobic) but dissolves readily in oil.

4. Soaps made from palmitic acid are known as sodium palmitate. Figure 5.2 shows the structure of the palmitate ion in soaps:

Figure 5.2

5. The figure 5.3 shows the molecular model of the palmitate ion and the simple representation of the structure of the palmitate ion:

Figure 5.3

DETERGENTS1.Detergents are synthetic cleaning agents made from hydrocarbons obtained from petroleum fractions. Thus, detergents are petrochemicals.

2. Detergents can be classified into three main types, depending on the charge on the detergent ion.

a) Anionic detergents where the head of the detergent particle contains negatively charged ion.

Example:

b) Cationic detergents where the head of the detergent particle contains positively charged ion.

Example:

c) Non-ionic detergents.

Example: R−O−CH 2 CH 2 OH

PREPARATION OF DETERGENTS1. The detergent, sodium alkyl sulphate can be prepared from alcohols with chain lengths of 12 to 18 carbon atoms in two steps.

Steps 1: Reaction with concentrated sulphuric acid

O O || ||R−O−H +H−O−S−O−H →R−O−S−O−H +H 2 O || || O Olong-chain alcohol concentrated suphuric alkyl hydrogen suplate acid

Step 2 : Neutralisation with sodium hydroxide solution.

O O || ||R−O−S−O−H +NaOH→R−O−S−O− Na++H 2 O

|| || O O Alkyl hydrogen sodium alkyl sulphate sulpathe

2.An example of a long chain alcohol is didecan –1 –ol, CH 3 (CH 2 )10 CH 2 OH . The detergent prepared from dodecan -1–ol is called sodium dodecyl sulphate (IUPAC

name) or sodium lauryl sulphate (common name), CH 3 (CH 2 ) 10 CH 2 O−SO 3− Na+

.

THE STRUCTURE OF DETERGENT MODULE

When a detergent is dissolved in water, it dissociates to form sodium ions and detergent ions. The detergent ions have the same basic structure as the soap ions, that is, it consists of two parts:

a) The ‘head’ is the suplate group (−OSO 3− ) which is negatively charged and

hydrophilic (dissolves readily in water but not in oils and grease) .

b) The ‘tail’ is the ling hydrocarbon chain, which is neutral and hydrophobic (dissolves readily in oils and grease but not in water) .

alkyl suphate ion

THE CLEANSING ACTION OF SOAP AND DETERGENT

1.The cleansing action of soap or detergent depends on their chemical bonding and structures.a)The ionic ‘head’ (negatively charged) is soluble in water (hydrophilic) but insoluble in oily layer.b)The long hydrocarbon ‘tail’ (neutral) is insoluble in water (hydrophobic) but soluble in oily layer.

2.Lifting greasy dirt from the surface cloth. When soap or detergent mixed with water is added to the surface of a piece of cloth covered with a layer of oil or grease. ( Figure 5.4(a) ) ,a)The negatively charged ‘head’ (hydrophilic) of soap ions or detergent ions dissolves in water.b)The hydrocarbon ‘tail’ (hydrophobic) of soap or detergent ions dissolves in the layer of grease.3.If the water is agitated slightly, the grease begins to be lift off the surface. ( Figure 5.4(b) ).4.On further agitation during washing, the greasy dirt is lifted from the surface. (Figure 5.4(c) ), since the density of grease is less than water.

6. Emulsifying dirt in water  a) When the water is shaken, the grease will be emulsified when it breaks into smaller droplets.b) These greasy droplets repel one another because they carry the same chrge. As a result, the grease is suspended in the solution.c) When the cloth is rinsed with water, the droplets will be carried away.d) The cleansing process becomes more efficient if the water containing the soap or detergent is stirred vigorously or the washing is done at a higer temperature. Heating and stirring help to loosen the dirt particles from the material being washed.

Figure 5.4  

ADDITIVES IN DETERGENTS 1.Modern detergents used for washing clothes usually contains a few types of additives to :a)Increase their cleaning power. b)Make them attractive and saleable.

2.Only about 20% of the substances in a detergent are cle4ansing agents (sodium alkyl sulphate or sodium alkylbenzene sulphonate). The other substances are additives. The examples of addictives and their functions are described as follows :

a)Builders : Sodium tripolyphosphate ( Na5 P 3 0 10 )

i) Sodium tripolyphospathe is usd to soften hard water and compromises about 40%

of the subtances in the detergent. In the presence of sodium tripolyphosphate,Ca2 +

ions andMg2+ions are removed.

ii)Sodium tripolyphosphate increases the pH value of water. In this way, muddy dirt can be removed.

b)Whitening / bleaching agents : sodium perborate

i) Bleaches (bleaching agents) remove coloured stains by oxidation process. Whencoloured stanis are oxidized, the colour will disappear.

ii) The whitening (bleaching) agents commonly used in detergent are sodium perborate . ( NaBo 2 . H 2 O 2 . 3 H 2 O ) .Sodium perborate decomposes in hot water to release oxygen (an oxidising agent) which is responsible for the whitening (bleaching) action.

c) Biological enzymes: Amylase, lipase amd protease.

i)Protein stains such blood, milk, and tomato sauce cannot be removed by the ordinary detergents because these types of stains are insoluble in water. ii)Biological enzymes in detergents can break down fat and protein molecules in foodstains. The fatty acids, glycerol and amino acids produced are soluble in water and areremoved during washing.

d)Brighteners

i) Figure below shows the action of brighteners. The brighteners absorb the invisible ultra-violet and re-radiate it as blue light.

ii)Brighteners make fabrics appear whiter and brighter because the blue light can hide any yellowing on the fabrics. Blue light added to the yellow light reflected on old fabrics make them look white.

e) Drying agents ; Sodium sulphate and sodium silicateAnhydrous sodium sulphate and sodium silicate ( Na2 . SiO 3 )are used as drying agents to ensure that the detergent in powdered firm is always in a dry condition.

f) Stabilisers

i)The functions of stabilizers is to prevent the formation of foam.

ii)In an automatic washing machine, excessive foam can stop the pump working. So,washing powders for automatic washing machine are made using detergents that are good at removing and emulsifying grease, but do not produced foam.

g) Perfumes

Perfumes are added to make clothes smell fresh and clean.

THE EFFECTIVENESS OF SOAPS AND DETERGENTS AS CLEAING

AGENTS

Advantages of Soaps1.Soaps are effective cleansing agents that are effective 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 chemicals found in animals and plants. This means that soaps are biodegradable.

Disadvantages of Soaps1. 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 Ca2 +

to form a precipitate called scum. 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.

Mg2+ (aq )+2 C 17 H 35 COO−(aq )→(C 17 H 35 COO )2 Mg( s ) stearate ion magnesium steroate (soap ion) (scum)

Ca2 +( aq)+2 C 17 H 35 COO−(aq )→(C 17 H 35 COO )2 Ca(s ) stearate ion calcium steroate (soap ion) (scum)

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.

C 17 H 35 COO−(aq )+H+ (aq )→C 17 H 35 COOH (s ) stearate ion stearic acid (soap ion)

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 (’heads’) 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 Mg2+ and Ca2 +

ions found in hard water.

2. The detergents ions (R –O – SO3 ) a n d react with Mg2+ and Ca2 +

ions in hard water. However, the magnesium salts and calcium salts which are formed are soluble in water.

2 R−O−SO 3− (aq )+Mg2+ ( aq)→(R−O−SO 3 ) 2 Mg (aq )

alkyl sulphate ion magnesium alkyl sulphate (detergent) (dissolves in water)

2 R−O−SO 3− (aq )+Ca2+ (aq )→( R−O−SO 3 )2 Ca( aq)

alkyl sulphate ion calcium alkyl sulphate (detergent) (dissolves 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 decompose 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 to die from oxygen starvation.

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

USE OF FOOD ADDITIVES

Food Additives1. Food preservatives have been used since ancient times. Ancient civilization used salt to preserve meat and fish, herbs and spices to improve the flavor of food.

2. Food additives are chemicals that are added to food in small quantities for specific purpose such as protection against bacterial attack or restoring the colour of the food destroyed during food processing.

TYPES OF FOOD ADDITIVES EXAMPLEPreservatives Sodium nitrite; sodium nitrate; benzoic

acid; sodium benzoate; sulphur dioxide;

FOOD ADDITIVES

flavouring agents dyes

stabilizer and thickening agents

preservatives and antioxidants

sodium sulphite; sorbic acidAntioxidants Ascorbic acid (Vitamin C); BHA; BHT;

citric acid; sodium citrateFlavouring agents Monosodium glutamate (MSG);

aspartameStabilizers and thickeningagents Gelatin; acacia gum (agar)Dyes Azo compounds; triphenyl compounds

Example of different types of food additivesFunctions of food additives

Preservatives

1. Preservatives are chemicals that are added to food to retard or to prevent the growth of microorganisms, so that the food can be stored for a long time.

2. In ancient times times, food additives from natural sources such as salt, sugar and vinegar were used to preserve food and to make the food taste better.

3. Nowadays, synthetic preservatives are used. Table 5.2 shows the type of preservatives commonly used. Many of the preservatives are organic acids and slats of organic acids.

Table 5.2 Type of preservatives and their usesPreservatives Molecular formula Uses

Sodium nitrite

Sodium nitrate

NaNO 2

NaNO 3

To preserve meat, sausage, cheese and dried fish

To prevent food poisoning in canned food

To maintain the natural colour of meat and to make them look fresh

Benzoic acid

Sodium benzoate

C 6 H 5 COOH

C 6 H 5 COONA

To preserve sauces (oyster, tomato or chili) , fruit juice, jam and margarine

Suplhur dioxide

Sodium sulphite

SO 2

Na2 SO 3

Used as bleaches and antioxidants to prevent browning

in fruit juices Maintain the colour

and freshness of vegetables

To prevent the growth of yeast

Antioxidants

1. Antioxidants are chemicals that are added to foods to prevent the oxidation of fats and oils by oxygen in the air.

2. Food containing fats or oils are oxidized and become rancid when exposed to air. This makes the food unpalatable. The rancid products are volatile organic compound

with foul odour. ( Example: Butanoic acid, C 3 H 7 COOH )

3. Antioxidants are added to fats, oils, cakes, sausages, biscuits and fried food to slow down the oxidation process.

Flavouring Agents

1. Flavouring agents are used to make food taste better.

2. There are two types of flavouring agents:

3. Flavour enhancers have little or no taste of their own. They are chemicals that are added to food to bring out the flavours or to enance the tastes of food. An example of a flavor enhancer is monosodium glutamate (MSG).

4. Artificial flavours include sweeteners and other flavours such as peppermint or vanilla. Aspartame and saccharin are examples of artificial sweeteners.

5. Both aspartame and saccharin can be used as a substitute for sugar to enhace the sweeteners in food and drinks. However the use of saccharin is banned is most countries because it is carcinogenic.

6. Many esters have fruity odours and tastes and are used as artificial flavours. Table 5.3 shows some examples of esters that are used in making drinks.

Table 5.3 Uses of esters as flavouring agentsEster Benzyl

ethanoateOctyle

ethanoateEthyl

butanoateFlavour Strawberry Orange Pineapple

Stabilizers and thickening agents

1. Stabilizers and thickening agents are used to improve the texture and blending of foods.

FLAVOURING AGENTS

flavour enhancers

artificial flavours

2. Stabilizers are chemicals that are added to enable oil and water in the food to mix together properly in order to form emulsion of water and oil. Examples of stabilizers are gelatin and acacia gum.

3. Stabilizers are added to improve the texture of food. For example, stabilizers are added to ice cream and peanut butter to keep them smooth and creamy.

4. Without stabilizers, ice crystals would form in ice creams, particles of chocolate would settle out of chocolate milk, oil and vinegar in salad dressing will separate as soon as the mixing is stopped. 3. Thickening agents are chemicals that are added to food to thicken the liquid and to prevent the food from becoming liquid. Thickening agents ( also called thickeners) absorb water and thicken the liquid in food to produce to produce jelly-like structure.

6. Most thickening agents are natural carbohydrates. Gelatin and pectin are added to help jams and jellies settle.

Dyes

1. Dyes ( colouring agents) are chemicals that are added to food to give them colour so as to improve their appearance.

2. Some food are naturally coloured, but the colour is lost during food processing. The food industry uses synthetic food colours to:a) restore the colour of food lost during food processingb) enhance natural colours, so as to increase the attractiveness of foodc) give colour to food that do not have colour

3. Some dyes are natural plant pigments while others are synthetically prepared. The synthetic colours used in food are azo and triphenyl compounds. Both these compounds are organic compunds.

4. The synthetic dye, brilliant blue, is an example of triphenyl compounds. The synthetic dye tartrazine and sunset yellow are examples of compounds.

5. Azo compounds are organic compounds containing the diazo group, −N=N− , and are usually yellow, red, brown or black in colour. Triphenyl compounds are organic

compunds containing three phenyl groups, −C 6 H 5 , and are usually green, blue or purple in colour.

EFFECTS OF FOOD ADDITIVES ON HEALTH

Effects Explanation

Allergy Caused by sodium sulphite, BHA

and BHT , MSG and food dyes( yellow No.5).

MSG allergy causes a disease named ‘Chinese restaurant syndrome’ (giddiness, chest pain and difficulty in breathing)

Cause ‘blue baby’ disease which is fatal. This is due to the lack of oxygen because of the presence of sodium nitrate /nitrite.

Cancer Caused by carcinogens (sodium nitrite).

Nitrite reacts with amines to produce nitrosamine which can cause cancer.

Brain damage Caused by excessive intake of nitrites.

The supply of oxygen to the brain is distrupted.

Hyperactivity Caused by tartrazine (additives)

Difficult to sleep or relax and felt restless.

READING THE FOOD LABEL

1. You must read the label on the food to identify:a) brand nameb) the net weightc) the Halal symbol for Muslim customersd) the nutrient content e) food additives usedf) expiry dateg) address of the manufacturers

2. Food additives listed in the food labels are usually represented by the code number – E. This code number shows that the food additives have been approved.

3. Figure 5.6 shows a food lable:

Figure 5.6 Food label

The rationale of using food additives

To prevent food

spoilage

To improve nutritional

valuesFor medical

reasons

Disadvantages of food

additives

Bad for health

Life without

food additives

Food spoilage

always occur

Disease will occur oftenly

Malnutrition will occur

particularly

MEDICINE

SOURCES AND USES OF TRADITIONAL MEDICINE1. Medicine is a substance used to prevent or cure diseases or to reduce pain and suffering due to illness.

2. Traditional medicine is a medicine derived from natural resources without being processed chemically.

3. Medicine obtained from plants are known as herbal medicines. The sources and uses of some herbal medicine are shown in Table 5.4.

Table 5.4 Some examples of herbal medicines

Plant Part of the plant used

Uses

Garlic Corm For preventing flue or asthma attacks. For reducing high blood pressure.

Ginger Rhizome ( horizontal underground stems)

For treating stomach pain due to wind in stomach.

For supplying heat energy to keep the body warm.

For preveting flu attack.Aloe vera Leaves For treating itchy skin

For trating burn (scalding) on the skinLemon (lime)

Fruits For treating boils or abscesses on the skin

For preventing flu attack For treating skin diseases

Quinine Bark of cinchona tree

For treating malaria For preventing muscle cramps

Ginseng Roots As a tonic to improve the overall health of human beings

For increasing energy, endurance and reduce fatigue

Lemon grass Stem/ Leaves Has antibacterial and antifungal properties

For treating coughsTongkat ali Roots As a tonic for after birth and general

health

MODERN MEDICINE1. Modern medicine can be classified as follows based on their effects on the

human body:a) Analgesicsb) Antibioticsc) Psychotherapeutic drugs

FUNCTION OF EACH TYPE OF MODERN DRUGS

Analgesics1. Analgesics are medicine that relieve pain. They are sometimes called as

painkillers.2. Aspirin and paracetamol are mild painkillers whereas codein is a powerful

painkiller.3. Analgesics relieve the pain but does not cure the disease. 4. Table 5.5 shows the types and functions of analgesics.

Antibiotics: Antibacterial Medicine

1. Antibiotics are chemicals that destroy and prevent the growth of infected microorganisms.

2. Two examples of antibiotics are penicillin and streptomycin.3. Antibiotics will not cure the infection caused by viruses such as cold and flu. 4. Table 5.6 shows types and functions of antibiotics.

Psychotherapeutic medicines1. Psychotherapeutic medicines are a group of dugs for treating mental and

emotional illness.2. Table 5.7 shows the types and functions of psychotherapeutic medicines.

Type of analgesic Uses Side effectsAspirin

Pain relief and anti-inflammatory action.

Acetyl salicylic acid (IUPAC name)

Contains 2 functional groups (carboxylic acid/ester)

Acidic.

o Reduce fevero Relieve headaches,

muscle aches and joint aches

o Treat arthritiso Acts as an anti

coagulant – prevent clotting blood.

o Reduce the risk of heart attack and strokes.

Cause brain and liver damage of ill children.

Cause bleeding in the stomach.

Cause allergy reactions, skin rashes, asthmatic attacks

Paracetamol neutral

o To relieve mild to moderate pain (headache ,muscle and joint pain, back ache , period pains)

o Does not irritate the stomach to bleed

Causes skin rashes, blood disorders and acute inflammation of the pancreas.

Cause liver damage.

Codeine Is an organic

compounds that contains carbon, hydrogen oxygen and nitrogen elements

o Used to relieve minor to moderate pain. It is more powerful than aspirin and paracetamol but less powerful than morphine. Codein and morphine are narcotic drugs.

o Also used in cough mixtures for suppressing coughs.

Can cause an addiction.

Table 5.5 Types, functions side effects of analgesics.

Table 5.6 Types, functions and side effects of antibiotic

Psychotherapeutic Medicines

Uses Side effects

StimulantsA medicine which activates the level of arousal and alertness of the central nervous system to reduce fatigue and elevate mood in most people.

i) AdrenalineA need in demanding energeticactivities.ii) Caffeineweak, naturally occuring stimulant found in coffee, tea and cola drinks.iii)AmphetaminesStrong synthetic stimulants

Increase alertness and physical ability.

Increase the heart respiration rates and blood pressure.

Cause addiction

AntidepressantsMedicine used primarily in the treatment of depression

i) tranquilizers - to calm down a person, reduce tension & anxiety

cause drowsiness, poor coordination and light headedness, respiratory difficulties ,sleeplessness , coma and

Antibiotics Uses Side effectsPenicillin

Derived from the mould penicillium chrysogenum.

Treat diseases caused by bacteria such as:

o pneumoniao gonorrheao syphilis.

Cause allergic reactions

Cause death for people who are allergic to it

Streptomycin Produced by soil

and bacteria at the genus streptomyces

Treat:o tuberculosiso whooping cougho some forms of

pneumonia.

Cause nausea, vomiting, dizziness, rashes and fever.

Loss of hearing following long term use

ii) Barbiturates - To sedate, calm and relax individual in low doses

death if overdose.

Cause sleep (high dose)

Cause addiction and habit forming

Cause deathAntipsychotic medicine To treat psychiatric illness such as

schizophrenia( loses touch with reality)

Cause dry mouth, blurred vision, urinary retention, tremor and less rest as well as sedation (more calmer/sleepy)

Table 5.7 Types, functions and side effects of psychotherapeutic medicines

Appreciating the Existence of Chemicals

1. Since the last 100 years, thousands of new chemicals are synthesized. These new chemicals include synthetic polymers, composite materials, antibiotics, detergents and modern medicines. These chemicals improve the quality of life.

2. Modern chemical substances have brought enormous benefits to mankind. However, the chemicals have side effects on life and the environment. We must practice proper management of chemicals toward a better life, hygiene and health.

Correct ways of

using medicine

Avoid self-medication

Visit doctor if there is any side effects

Know the required

dosage for each age

group

Check the expiry date

Follow the intructions

given

3. Intensive scientific research must be carried out to produce new substances and this takes time. Scientists must have patience, meticulousness and perseverance for their research and development to produce new products.

4. Modern living depends on chemical substances. Try to imagine the world without chemicals. For example, without petroleum, the transport system will break down. Without modern medicine, diseases will spread and without soap and detergent, the world will become more dirty and unhygienic.