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7/23/2019 Chemistry Folio Form 5 Chapter 5 Chemicals for Consumers
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CONTENTS
PAGEIntroduction 35.1 Soap and Detergent
5.1.1 The History Of Soap Manufacturing5.1.2 Preparation Of Soap By Saponification
How to prepare soap by using saponification in thelaboratory
5.1.3 Types Of Soap5.1.4 Detergents
Preparation Of Detergents5.1.4a The Structure Of Detergent Molecule5.1.4b The Cleansing Action Of Soap And Detergent5.1.4c Additives In Detergents5.1.5 The Effectiveness Of Soaps And Detergents As Cleansing
Agents
45
6-78
9101112
13-141516
5.2 Food Additives5.2.1 Effect Of Food Additives On Health
17-2223
5.3 Medicines 24-265.4 The Existence Of Chemicals 27Conclusion 28
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INTRODUCTION
Chemistry is the science of matter. All objects that exist around us are made of
chemical substances. Without chemistry, life itself would be impossible. All
objects contributed an endless of benefits to mankind. As time continued to
unravel, humans had done their best to delve into this subject to ensure that all the
chemical substances are exploited and utilized to the fullest and simultaneously,
improve the quality of life of mankind.
The discovery of chemicals manufactured for consumers such as cleaning agents,
food additives and medicines has helped us improve our health and standard ofliving. Today, different types of chemicals are produced to meet the needs and
preferences of consumers. Therefore, understanding the chemistry of these
chemicals will help a consumer select and use them wisely.
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5.1 SOAP AND DETERGENT
What is soap?
Soap are sodium or potassium salts
of long-chain carboxylic acids
The general formula of a soap :
RCOO-Na+/ RCOO-K
+, where R is an
alkyl group which contain 12 to 18
carbon atoms. R can be saturated or
unsaturated.
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5.1.1 THE HISTORY OF SOAP MANUFACTURING
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5.1.2 PREPARATION OF SOAP BY
SAPONIFICATION
Soaps are prepared by hydrolysing fats or oils under alkaline
condition. The reaction is called saponification.
Fats/Vegetable oils + Concentrated alkalis Soap + Glycerol
(Fats: tallow from cow)
(Vegetable oils: Palm oil/Olive oil)
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The soap molecule has two parts: a polar group (-COO-Na+) and a non-polar
group (R-hydrocarbon part).
The polar group is called the head and the non-polar group is called the tail.
Thus, the soap molecule has a polar head and a non-polar hydrocarbon tail. The polar head is hydrophilic in nature (water loving) and the non-polar tail is
hydrophobic (water repelling) in nature.
The saponi fi cation reaction is exothermic in nature, because heat is liberated
during the process. The soap formed remains in suspension form in the mixture.
Soap is precipitated as a solid from the suspension by adding common salt to the
suspension. This process is called Salting out of Soap.
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How to prepare soap by using saponification in the
laboratory
Take 25 ml of coconut oil in a measuring cylinder
and pour it into a 250 ml glass beaker.
Measure 30 ml of 20% NaOH solution in another
measuring cylinder and add it into the beaker
containing vegetable oil.
Then the mixture is stirred vigorously
Place the beaker on a wire gauze
placed over a tripod stand.
Heat the beaker using a Bunsen
burner till the mixture become a
whitish paste.
Remove the beaker from the
flame and allow it to cool.
To the above suspension,
add 15g of common salt
and stir it well with a glass
rod.
After adding common salt,
soap in the suspension gets
precipitated out as solid.
Pour the contents of the
beaker into the funnel ove
a glass rod and filter the
contents of the beaker.
After filtration, soap is lef
behind in the filter paper.
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5.1.3 TYPES OF SOAP
Depending upon the nature of alkali used in the production of soap, they
are classified into two types.
I. Hard soap
The sodium salt of long chain fatty acid is known as hard soap . It is difficult to
dissolve in water. It is used as laundry soap.
II. Soft soap
The potassium salt of long chain fatty acid is known as soft soap, as it produces
more lather. It is used as toi let soap and shaving soap.
In aqueous solution, soap ionises to form alkali ions.
Since soaps have free alkali ions, they are alkaline in nature. Hence, the soap
solutions are slippery to the touch.
Some examples of soaps are shown below.
a) Sodium palmitate, C15H31COONab) Sodium oleate, C17H33COONa
c) Sodium stearate, C17H35COONa
Additives such as perfume, colouring matter and sometimes antiseptics are
added to soaps to enhance their marketability.
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5.1.4 DETERGENT
Detergent is a synthetic cleansing agents which is made from
hydrocarbons obtained from petroleum fr action.Thus, detergents are
petrochemicals.
Detergents
Anionic detergents
where the head ofthe detergent particle
contains anegatively chargedion.
R
O
SO3-Na+
(Sodium alkyl sulphate)
Cationic detergents
Cationic detergents wherethe head
of the detergent particle
contains apositively chargedion.
R N (CH3)3+BR-
Non ionic detergent
R O CH2CH2OH
Further divided into
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Preparation Of Detergents
Sodium alkyl sulphate Sodium alkylbenzene sulphonates
- can be prepared from alcohols with chain
lengths of 12 to 18 carbon atoms.
- Step 1:Reaction with Concentrated sulphuric acid
Step 2 :
Neutralisation with sodium hydroxide solution
Starting materials
- long chain alkene, RCH = CH , obtained
from the cracking of petroleum.
Step 1 :
Alkylation ( introduction of the alkyl group to
an organic molecule)
Step 2 :
Sulphonation ( introduction of the sulphonic
acid group to an organic molecule to form
sulphonic acid)
Step 3 :
Neutralisation
Alkylbenzene sulphonic acid produced reacted
with sodium hydroxide to form sodium
alkylbenzene sulphonate, the detergent
Example :
An example of a long chain alcohol isdidecan 1ol, CH3(CH2)10CH2OH
Detergent prepared from dodecan1olis called sodium dodecyl sulphate /
sodium lauryl sulphate
CH3(CH2)10CH2O-SO3-Na
+
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5.1.4a THE STRUCTURE OF DETERGENT
MOLECULE
When a detergent is dissolved in water, it dissociates to form sodium ions (Na+) anddetergent ions. The detergent ions have the same basic structure as the soap ions, thatis consist of two parts :
a) The head is the sulphate group (-OSO3-), which is negatively charged and
hydrophilic (dissolves readily in water but not in oils and grease).
b) The tail is the long hydrocarbon chain, which is neutral and hydrophobic(dissolves readily in oils and grease, but not in water).
Hydrophilic head
Hydrophobic tail
(Hydrophobic)
oso3
-
Ionic head
(Hydrophilic)
Hydrophobic tail
(Hydrophobic)
so3
-
Ionic head
(Hydrophilic)
Figure 5.1.4a - Alkyl sulphate ion
Figure 5.1.4b - Alkylbenzene
sulphonate ion
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5.1.4b THE CLEANSING ACTION OF SOAP AND
DETERGENT
The cleansing action of soap and detergent The cleansing action of soaps and detergent results from
the ability to lower the surface tension of water,
to emulsify oil/ grease and
to hold them in suspension in water
This can be occurred due to theirchemical bonding and the structure.Oil cannot be washed away from clothing with water only as it is a
covalent molecule which is insoluble in water.
I. Lifting greasy dirt from the surface cloth. 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 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.
II. The water is agitated slightly, the grease begins to be lifted off the surface. Thiscause by the forces of attraction between the water molecules and the negatively
charged heads.
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III. On further agitation during washing, the greasy dirt is lifted from the surface.
IV. Emulsifying dirt in water
a) Soaps and detergents can act as emulsifying agents to emulsify oils and grease.
b) The process of emulsification breaks large drops of grease into smaller droplets that
floats in water. The greasy droplets repel on another because they carry the same charge.
As a result, the grease is suspended in the solution.
c) When the cloth is rinsed with the water, the droplet will be carried away.
d) The cleaning process become more efficient in the water containing the soap or detergent
solution is stirred
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5.1.4c ADDITIVES IN DETERGENTS
ADDITIVES FUNCTION EXAMPLE
Builders -To enhance the cleaning efficiency ofdetergent by softening the water.
-To increase the pH value of water.
Sodium tripolyphosphate
Drying agents -To ensure that the detergent in powdered form
is always in dry condition.-To add to the bulk of the detergent and enable
to pour it at ease.
Sodium sulphate
Sodium silicate
Fragrances -To add fragrance to both detergent and fabrics.
Foam control agents -To control foaming in detergent.
Optical whitener -To add brightness and whiteness to whitefabrics.
Fluorescent dyes
Suspension agents -To prevent dirt particles removed fromredepositing onto cleaned fabrics.
Carboxymethylcellulose(CMC)
Biological enzymes -To remove protein stains such as blood.
-To break down fat and protein molecules infood stains.
Amylases ,proteases,
cellulases and lipases
Whitening agents -To convert stains into colourless substances.-To make the fabrics whiter and more beautiful.
Sodium perborateSodium hypochlorite
(NaClO)
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5.1.5 THE EFFECTIVENESS OF SOAPS AND
DETERGENTS AS CLEANSING AGENTSCleansing
agents
Advantages Disadvantages
Soap 1. Very effective in soft water to wash
clothes.( water does not contain Mg+
&Ca
+ions)
2. Do not cause pollution as soaps are
made from fats and oils and can bedecomposed by the action of bacteria.
1. Ineffective in hard water.
2. A grey scum (Magnesium stearate &
calcium stearate) will be produced in hardwater.
3. Not effective in acid water.( exist as
molecules & do not have hydrophilic ends)- H ion from rainwater (acid) will react
with soap ions to produce carboxylic acidmolecules of large molecular size that are
insoluble in water. Example,
Detergent 1. Effective in soft water and hard water.
( magnesium salt and calcium salts areformed and soluble in water)
( scum is not formed)
2. Synthetic cleansing agents- Structure of hydrocarbon chain can be
modified to produce detergent.
3. Effective in acidic water as H ions isnot combining with detergent ions.
1. Non-biodegradable
2. Water pollution occurs.
3. Decrease in oxygen content in water and
the aquatic lives are given theharm.( phosphates in detergents)
4. a lot of foam will be produced in water
that prevent oxygen from dissolving inwater. As a result, fish and other aquatic
lives face the death.
5. Additives (sodium hypochlorite) releaseschlorine gas that is highly toxic and kills
aquatic life.
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5.2 FOOD ADDITIVES
Food preservative have been used since ancient times. Ancient civilization
used salt to preserve meat and fish, herbs and spices to improve the flavor offood.
Food additives are chemicals that are added to food in small quanti ties for
specif ic purposes such as protection against bacter ial attack or restoring the
colour of food destroyed dur ing food processing.
Food additives are used :
i) prevent spoilage
ii) improve its appaerance , taste or texture
iii) prevent growth of microorganisms
iv) prevent oxidation of fats and oils by oxygen in air
v) restore the colour of food destroyed during food processing.
Two Main Groupof Food
Additives
Preservatives and
Antioxidants
to protect food from being
spoiled by bacterial attact or
atmospheric oxidation.
Flavouring agents,
stabilizers, thickening agents(thickeners), and dyes
to enhance the taste, smell and
appearance of the food.
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Table below show a list of different types of food additives and examples of each
types.
Type of food
additive
Examples of food additive
Preservatives Sodium nitrite ; sodium nitrate ; benzoic acid ; sodium benzoate ;
sulphur dioxide ; sodium sulphite ; sorbic acid ; sodium sorbate
Antioxidants Ascorbic acid (vitamin C) ; BHA (butylated hydroxyanisole) ;BHT (butylated hydrixitoluene) ; citric acid ; sodim citrate
Flavouring agents Monosodium glutamate (MSG) ; aspartame
Stabilisers and
thickening agents
Gelatin ; acacia gum (agar)
Dyes (colouring
agents)
Azo compounds ; tripheny compounds
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I. PRESERVATIVES
Preservatives are chemicals that are added to food to retard or to prevent
the growth of microorgani sm such as bacter ia, mould or fungus, so thatthe food can be stored for a long time.
In ancient times, food additives from natural sources such as salt, sugar and vinegar were
used to preserve food and to make the food taste better.
Nowadays, synthetic preservatives are used, table below shows the types of preservatives
commonly used. Many of the preservatives are organic acids and salts of organic acids.
Examples;
PRESERVATIVE MOLECULAR
FORMULA
USES
Sodium nitrite
Sodium nitrate
NaNO2
NaNO3
To preserve meat, cheese and dried fish. To prevent food poisoning in canned foods. To maintain the natural colour of meat and to
make them look fresh
Benzoic acid
Sodium benzoate
C6H5COOH
C6H5COONa
To preserve sauce (olyster, tomato or chilli),fruit juice, jam and margarine
Sulphur dioxide
Sodium sulphite
SO2
Na2SO3
Used as bleaches and antioxidants to preventbrowning in fruit juices.
Maintain the colour and freshness ofvegetables.
To prevents the growth of yeast
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II. ANTIOXIDANTS
Antioxidants are chemicals that are added to foods to prevent the
oxidation of fats and oils by oxygen i n the air .
Foods containing fats or oils are oxidized and become rancid when exposed to air.
When the fats and oils are oxidized, rancid product are formed. This makes the food
unpalatable. The rancid product are volatile organic compound with foul odours (for
example , butanoic acid, C3H7COOH).
Antioxidants are added to fats, oils, cakes, sausages, biscuits and fried foods to slow
down the oxidation process so that these foods do not become rancid.
III. FLAVOURING AGENTS
There are two types of flavouring agents : artificial flavours and flavour
enhancer. They are added to foods to make them taste better.
1. F lavour enhancer have li ttle or no taste of their own. They are chemicals that are added
to food to bring out the flavours or to enhance the taste of food.
2. An example of a flavour enhancer is monosodium glutamate (MSG). MSG is used to
enhance the flavours of other foods.
3. Artificial flavour includes sweeteners and other flavours such as peppermint or vanilla.
Aspartame and saccharin are examples of artificial sweeteners.
4. Both aspartame and saccharin can be used as a substitute for sugar to enhance thesweetness in food and drink.However, the used of saccharin is banned in many
countries because it is carcinogenic. Aspartame has largely replaced saccharin as the
artificial sweetener or choice.
5. Many esters have fruity odours and tastes and are used as artificial flavours. Table below
shows some examples of esters that are used in making drinks.
Ester Benzyl
ethanoate
Octyl ethanoate Ethyl
butanoate
Flavour Strawberry Orange Pineapple
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IV. STABILISERS & THICKENING AGENTS
Stabilisers and thickening agentsimprove the texture and the blending of
foods.
Stabilisers are chemicals that are used to enable oil and water in the food
to mix together proper ly in order to form an emulsion of oil and water .
Examples of stabili zers are gelatin and acacia gum.
1. Stabilisers are added to improve the texture of foods. For examples, stabi li sers are
added to i ce-cream and peanut butter to keep them smooth and creamy.
2. In the presence of stabilisers, the emulsion of oil does not separate from water. This
means that the stabiliser improves the stability of some foods such as ice-cream and
salad dressings (mayonnaise).
3. Without stabilisers, ice crystals would form in ice-cream, particles of chocolate
would settle out of chocolate milk, oil and vinegar in salad dressing will separate as
soon as mixing is stopped.
Thickening agents are chemicals that are added to foods to thi cken the
liquid and to prevent the foods fr om becoming liquid. Thickening agents
(also called thickeners) absorb water and thicken the li quid in foods to
produce a jell y-like structure.
1. Most thickening agents are natural carbohydrates. Gelatin and pectin are added to
help jams and jellies to set.
Thickeners ExplanationModified starch Used in instant soups and puddings.
pectin Used in jams and jellies.Forms a firm jel when there is sufficient sugar in a mixture.
Is not digested.Can be considered as a beneficial and dietary fibre.
Acacia gum To thicken chewing gum, jelly and wine.
Gelatine To thicken yogurt.
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V. DYES
Dyes (colouring agents) arechemicals that are added to foods to give them
colour so as to improve their appearance.
1. Some foods are naturally coloured, but the colour is lost during food processing. The
foods industry uses synthetic food colours to :
a) Restore the colour of food lost during food processing.
b) Enhance natural colours, so as to increase the attractiveness of foods.
c) Give colour to foods that do not have colour.
2. Some dyes are naturally plant pigments while others are synthetically prepared. The
synthetic colours used in foods are azo and triphenyl compounds. Both these compounds
are organic compounds.3. The synthetic dyes , brilliant blue, is an example of triphenyl compound. The synthetic
dye, tartrazine and sunset yellow are examples of azo compounds.
4. Azo compounds are organic compounds containing the diazo group, - N = N -, and are
usually yellow , red, brown, black in colour. Triphenyl compounds are organic
compounds containing three phenyl groups, -C6H5, and are usually green. Blue or purple
in colour.
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5.2.1 EFFECT OF FOOD ADDITIVES ON HEALTH
Effects ExplanationAllergy Caused by Sodium sulphite, BHA and BHT , MSG and food
dyes( yellow No.5).
Cause an diseases named Chinese restaurant syndrome(giddiness, chest pain and difficulty in breathing)
Cause blue baby diseases occuring on babies which iitssynptoms is lacking of oxygen and the presence of sodium
nitrate /nitrite.
Cancer Caused by carcinogens(sodium nitrite) Nitrite reacts with amines to produce nitrosamine( cause
cancer)
Brain damage Caused by excessive intake of nitrites.Hyperactivity Caused by tartrazine (additives)
Difficul to sleep or relax and felt restles.
The Rationale for Using Food Additives
Advantages
To prevent
food spoilage.
To improve
nutritionalvalue
Medical reasons
Life without food
additives
Food
spoilage
always
occurDiseases will
occur often
Malnutrition
will occur
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5.3 MEDICINES
A medicine is a substance used to pr event or cure diseases or to reducepain and suf fer ing due to il lnesses.
It is classified as;
a. Traditional Medicines
Traditional medicines are medicines derived from natural sources such as plants andanimals without being processed chemically.
Since ancients, mankind had used various types of plants and roots, animals and animal
part to cure diseases.
Medicines obtained from plants are known as herbal medicines. The sources and uses of some
herbal medicines are shown in table below :
Plant Part of the plant
used
Uses
Garlic Corm For preventing flu attack
For reducing high blood pressure
Ginger Rhizome (horizontal
underground stem)
and leaves
For treating stomach pain due to
wind in the stomach
For supplying heat energy to keepthe body warm
For preventing flu attack
Aloe vera Leaves For preventing itchy skin
For treating burns (scalding) on the
skin
Lemon (lime) Fruits For treating boils or abscesses on theskin
For preventing flu attack
For treating skin diseases
Quinine Bark of Chinchona
tree
For treating malaria
For preventing muscle crampsGinseng Roots As a tonic to improve the overall
health of human beings
For increasing energy, endurance and
reducing fatigue
Lemon grass Stem/leaves Has antibacterial and antifungalproperties
For treating cough
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b. Modern Medicines
Modern medicines can be classified as follows based on their effects on the human body.
Some examples of modern medicines are analgesics, anti biotics, psychotherapeuti cdrugs.
Modern medicines usually contain a mix ture of active ingredients prepared in
dif ferent forms, such as capsul es, pi l ls, solu tions or suspensions.
Type Example Function Side Effects
ANALGESICSTo relieve pain
without causingnumbness/affectin
g conciousness
Aspirin Used for painrelief such as
arthritic painand dental
pain
- Cause internalbleeding and
ulceration- Can cause
brain and liverdamage if
given tochildren with
flu/chickenpox
Paracetamol Used forrelieve mild
to moderatepain such as
headache,muscle and
joint pain
- If overdose, itcan cause
liver damage
Codeine Used in
headachetablets and in
coughmedicines
- Can causedrowsiness
- If overdose, itcan lead toaddiction,
depression andnausea
ANTIBIOTICSTo kill/slow down
the growth ofbacteria
Penicillin Used to curetuberculosis
andpneumonia
- headache,allergic
reaction,diarrhoea
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Streptomycin
PSYCHOTHERA
PEUTIC DRUGS
To alter abnormalthinking, feelings
and behaviors
StimulantEg: Methylpenidate
To reducefatigue and
elevate mood
- If overdose,can lead to
anxiety,hallucinations
and severedepression
AntidepressantEg: Tranquilisers
Eg: Barbiturates
To reducetension and
anxiety
- Drowsiness,poor
coordination- If overdose,
can lead torespiratory
problems,coma and even
death
- Addiction- Can lead to
involuntary
death
especially forpeople whoused it to fight
againstinsomnia
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5.4 THE EXISTENCE OF CHEMICALS
The chemicals for consumers such as soap, detergents , food additives andmedicine play an important role in our life . However, they can contribute
negative effects to our health and the environment if these chemicals are
not used wisely .
Some proper management of these chemicals :-
Detergents
Wear gloves when working with strong detergents to protect your hands .
Use biodegradable detergents .Use appropriate amounts of detergents.
Food additives
Be wise when we consume the food with food additives.
Avoid consuming too much salt and sugar .
Avoid foods with additives which you are sensitive to .
Avoid rewarding children with junk food .
Medicines
No self medication .
Do not take medicine prescribed for someone else .
Check for expiry date .
Follow your doctors instruction for taking medicine .
Keep away from children .
Do not overdose .
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CONCLUSION
Without doubt, these chemicals have improved our standards of living. But we
have to remember that these chemicals must be used accordingly not abusively andintensive scientific research must be carried out to produce new substances and thistakes more time . Scientists must patient and persevere for their research and
development to produce new chemicals in future .