Rossita Radzak SASER

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CHEMICALS FOR CONSUMERS 1. (a) A student washed his socks which had oily stains. Explain the cleansing action of soap on the oily stains.

In water soap ionizes to form ions/anion CH3(CH2)x COO- and cation, sodium ions, Na+

The anions consists of hydrophilic part ( -COO -) and hydrophobic part (hydrocarbon) Hydrophilic part dissolve in water only but hydrophobic part dissolve in grease only The anions reduces surface tension of water, causing wetting of greasy surface. During washing and scrubbing, the anions pull the grease and lifted it off the surface and

break it into a small droplets (Emulsifying agent) Rinsing away the dirty water removes the grease (the dirt) and excess soap and the

surface is clean. Preparation of soap Procedure

1. pour 10 cm3 palm oil ( vegetable oil ) into a beaker 2. add 50 cm3 of 5.0 mol dm-3 NaOH / KOH solution 3. heat the mixture for (10 minutes) 4. stir 5. stop heating 6. add 50 cm3 distilled water and solid NaCl 7. boil the mixture for 5 minutes 8. cool 9. filter 10. wash / rinse 11. dry ( press the residue between filter papers Test 12. place a small amount of the residue into a test tube add distilled water, shake it well.

produce a lot of lather ( very foamy) Observation : white solid, slippery and produce a lot of lather ( very foamy). (b) Another student carried out four experiments to investigate the cleansing effect of soap and detergent on oily stains in soft water and hard water respectively.

Rossita Radzak SASER

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Compare the cleansing effect between (i) Experiments I and II (ii) Experiment II and IV Explain the differences in the observation Exp. I and II

The oily stain disappears in Experiment I but remains oily in Experiment II. Hard water contains Ca2+ and Mg2+ ions which reacts with soap ions to form scum (insoluble salt) The formation of scum makes anions less efficient for cleaning the oily stain on the sock In soft water, all anions are used to clean the oily stain Thus, soap is only effective as a cleansing agent in soft water and ineffective in hard

water. Exp. II and IV

The sock in Experiment II remains oily but is clean in experiment IV. The soap anions form scum when reacts with Ca2+ and Mg2+ ions in hard water. The formation of scum makes anions less efficient for cleaning The detergent anions CH3(CH2)x OSO3

- / CH3(CH2)x SO3- do not form a

precipitate with Ca2+ and Mg2+ in hard water. Hence, detergent cleans effectively in hard water but soap does not clean effectively in

hard water.

O

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Compare and contrast soap and detergent

Soap Detergent

Sodium carboxylate Sodium alkyl sulphate Sodium alkylbenzene sulphonate

Material : fat, vegetable oil, NaOH / KOH, mol dm-3

Petroleum fractions : long chain alcohol, NaOH / KOH, 5 mol dm-3 , H2SO4

Petroleum fractions : long chain alkene, NaOH / KOH, 5 mol dm-3, H2SO4

Preparation Saponification

Preparation 1. sulphonation 2. neutralization

Preparation 1. alkylation 2. sulphonation 3. neutralization

Food additive

Type Function Examples

Preservatives To slow down/ prevent the growth of microorganism, therefore food can kept for longer periods of time

Salts/sugar: draws the water out of the cells of microorganism and retards the growth of microorganism Vinegar: provides an acidic condition that inhibits the growth of microorganism. NaNO3 (Burger) Benzoic acid / sodium benzoate: to slow down the growth of microorganism

Antioxidants To prevent oxidation that can causes rancid fats and brown fruits

Ascorbic acid and vitamin E (Tocopherol)

Flavourings To improve the taste of food and restore taste loss because of processing

Sugar , salt, MSG, vinegar, aspartame and synthetic essences (ester)

Stabilizers To prevent emulsion from separating out.

Lecithin, fatty acid

Thickeners Its use to thicken foods Pectin, acacia gum, gelatine Dyes To add or restore the colour in

food in order to enhance its visual appeal and match consumers expectations.

Natural dyes and artificial dyes: Azo compounds or triphenyl compound.

CH3 (CH2)15 COO- Na+

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Medicine

Type Function Example Effect on health

Analgesic To relieve pain without affected consciousness

Aspirin Paracetamol Codeine

-Internal bleeding and ulceration -can cause brain and liver damage to children Over dose can cause brain and liver damage Addiction, depression and nausea

Antibiotics To treat infections cause by bacteria (tuberculosis, TB). Can kill or slow down the growth of bacteria.

Penicillin, streptomycin

Psychotherapeutic To alter the abnormal thinking, feelings and behaviors. Divide into 3 categories : a) stimulant: to reduce fatigue b) antidepressant: to reduce tension and anxiety c) antipsychotic: to treat psychiatric illness

-amphetamine -barbiturate / tranquilizer -chlorpromazine -haloperidol, clozapine

-High dose can lead to anxiety, hallucinations, severe depression, and psychological dependence. Overdose can lead to respiratory difficulties, sleeplessness, come, death. -dizziness, drowsiness, rapid heartbeat.

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The additives in detergent

Type Function Example Fragrances To add fragrance to both the detergent

and fabrics

Biological enzymes To remove protein stains such as blood Amylases, proteases, celluloses, lipases

Whitening agents To convert stains into colourless substances

Sodium perborate

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

Carboxymethylcellulose (CMC)

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

Sodium sulphate, sodium silicate

Optical whitening To add brightness and whiteness to white fabrics.

Fluorescent dyes

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

Sodium tripolyphosphate