Chemistry notes, chapter 5
Consumer and industrial chemistry
Textbook Chemistry Form 5 (DLP), pages 164–196
What this chapter covers
- Compare oils and fats, explain hydrogenation of unsaturated fats and justify the uses of oils and fats (5.1)
- Describe soaps and detergents, their preparation and cleansing action, and compare their effectiveness (5.2)
- Describe the types of food additives, their functions and examples, and justify their use (5.3)
- Explain types of traditional and modern medicines, their side effects, and cosmetics (5.4)
- Explain nanotechnology and graphene and describe applications of nanotechnology in daily life (5.5)
- Explain Green Technology and its application in waste and industrial wastewater management (5.6)
5.1Oils and fats
Oils and fats are esters formed when fatty acids react with glycerol (propane-1,2,3-triol). One glycerol molecule joins to three fatty acid molecules, so they are also called triglycerides.
Fatty acids are long-chain carboxylic acids (examples: palmitic, stearic and linoleic acid). The type of fatty acid decides whether the product behaves as an oil or a fat.
| Aspect | Oils | Fats |
|---|---|---|
| Source | Plants | Animals |
| State at room temperature | Liquid | Solid |
| Melting point | Low | High |
| Fatty acids | High percentage of unsaturated fatty acids | High percentage of saturated fatty acids |
| Example | Palm oil | Butter |
Palm oil is an oil (liquid, from a plant). Butter is a fat. Do not say "oils and fats are different homologous series": both belong to the ester homologous series.
Saturated and unsaturated
- Saturated fatty acids have only single C–C bonds (examples: palmitic, lauric, stearic acid).
- Unsaturated fatty acids have at least one C=C double bond (examples: oleic, linoleic, linolenic acid). The double bond lowers the melting point, so unsaturated fats are liquid.
Hydrogenation: unsaturated to saturated
Hot oil reacts with hydrogen gas, H2, using nickel as the catalyst. The C=C bonds open and hydrogen atoms are added to the chain.
Effect of hydrogenationUnsaturated oil + H2 → (Ni catalyst) saturated fat. The molecular mass rises, so the melting and boiling points rise. This is why margarine, made from oil, is solid at room temperature.
Uses of oils and fats
| Use | How |
|---|---|
| Nutrition | Supply energy and help absorb vitamins A, D, E and K; insulate the body |
| Biofuel | Biodiesel for diesel engines |
| Soap and personal care | Main raw material of soap; used in moisturisers |
| Animal feed | Meets the nutritional needs of cattle |
Too much fat, especially saturated fat from animals, raises the risk of heart problems, obesity and hardening of the arteries (arteriosclerosis).
Why do oils and fats with a high percentage of unsaturated fatty acids turn rancid more easily? Which has the better shelf life, an oil or a fat?
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The C=C double bonds are easily oxidised by oxygen in the air. Fats (saturated) last longer than oils.
5.2Cleaning agents
Soap is a sodium or potassium salt of a fatty acid, general formula RCOO−Na+ or RCOO−K+ (R has usually 12 to 20 carbon atoms). Detergent is a non-soap cleaning agent, a sodium salt of a sulphonic acid, usually made from petroleum fractions.
| Aspect | Soap | Detergent |
|---|---|---|
| Raw materials | Natural oils or fats and concentrated alkali | Petroleum fractions and concentrated sulphuric acid |
| Process | Saponification (alkaline hydrolysis) | Sulphonation, then neutralisation |
| Products | Soap + glycerol | Sodium alkyl sulphate or sodium alkylbenzene sulphonate + water |
| Examples | Sodium laurate, sodium palmitate | Sodium alkyl sulphate, ROSO3−Na+ |
Preparing soap: saponification
SaponificationOil or fat + concentrated NaOH (or KOH) → soap + glycerol.
Sodium hydroxide gives sodium soap, potassium hydroxide gives potassium soap.
Stearic acid + NaOH → sodium stearate + H2O: C17H35COOH + NaOH → C17H35COONa + H2O (neutralisation of the fatty acid).
Sodium hydroxide gives sodium soap, potassium hydroxide gives potassium soap.
Stearic acid + NaOH → sodium stearate + H2O: C17H35COOH + NaOH → C17H35COONa + H2O (neutralisation of the fatty acid).
Preparing detergent
- Sulphonation: alkylbenzene (or long-chain alcohol) reacts with concentrated H2SO4 to give a sulphonic acid and water.
- Neutralisation: the acid reacts with NaOH to form the detergent salt and water.
Cleansing action
Soap and detergent anions have two ends: a hydrophilic part (dissolves in water) and a hydrophobic part (dissolves in oil or grease).
- The anions lower the surface tension of water, so water wets the cloth better.
- The hydrophobic parts dissolve in grease, the hydrophilic parts stay in water.
- Scrubbing pulls the grease off the cloth; it breaks into small droplets surrounded by anions.
- The droplets repel one another (negative charges), cannot re-attach and are suspended in water as an emulsion, which is rinsed away.
Textbook crop: Chemistry Form 5 (DLP), Figure 5.10, p. 174.
Soap versus detergent
| Water | Soap | Detergent |
|---|---|---|
| Soft water | Effective | Effective |
| Hard water (Ca2+, Mg2+) | Less effective: insoluble scum (e.g. calcium stearate) forms, wasting soap | Effective: calcium and magnesium salts of detergent are soluble |
| Acidic water | Not effective: insoluble fatty acid forms | Effective: the acid formed is soluble |
Scum equation: 2C17H35COO−(aq) + Ca2+(aq) → (C17H35COO)2Ca(s).
Additives in detergents
| Additive | Function | Example |
|---|---|---|
| Biological enzyme | Removes protein stains such as blood | Protease, lipase |
| Whitening agent | Changes dirt to a colourless substance | Sodium perborate |
| Optical whitener | Makes clothes whiter and brighter | Fluorescent dyes |
| Water softener (builder) | Softens water so the detergent works better | Sodium tripolyphosphate |
| Foam control agent | Controls foam | Alkyl monoethanolamide |
| Anti-suspension agent | Stops removed dirt redepositing on clothes | Sodium carboxymethylcellulose |
| Fragrance | Pleasant smell | Jasmine, lavender |
| Drying agent | Keeps powder dry | Sodium sulphate |
A pupil washes a greasy shirt in hard water using soap and gets a white solid. Name the solid and explain why more soap is needed.
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Scum, calcium or magnesium stearate. Soap anions react with Ca2+/Mg2+ and are used up, so fewer anions are left to clean.
5.3Food additives
Food additives are natural or synthetic substances added to food to prevent spoilage or to improve its appearance, taste or texture.
| Type | Function | Examples |
|---|---|---|
| Preservatives | Prevent or delay growth of bacteria and fungi | Salt, sugar, vinegar, sodium benzoate, sodium nitrite |
| Antioxidants | Slow down oxidation of fats, prevent rancidity | Ascorbic acid, citric acid, tocopherol (vitamin E) |
| Flavourings | Add or restore flavour | MSG, aspartame, stevia, esters such as ethyl ethanoate |
| Stabilisers | Give a smooth, uniform texture | Pectin, agar |
| Emulsifiers | Let two immiscible liquids mix | Lecithin, monoglycerides |
| Thickeners | Thicken liquids | Starch, gelatine, xanthan gum |
| Dyes | Add or restore colour | Azo compounds, caramel |
Justifying the use of additives
- Food stays fresh and lasts longer; seasonal foods can be enjoyed all year; food looks better and tastes better.
- Taken in excess they may cause allergies, asthma, rashes, hyperactivity in children, nerve disorders and even cancer. Producers must follow the permitted amounts (Food Act 1983, Food Regulations 1985).
Antioxidants and preservatives are not the same: preservatives stop microbes, antioxidants stop oxygen reacting with fats.
A pupil adds ascorbic acid to cooking oil. Which type of additive is this and what does it do?
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Antioxidant; it slows oxidation of the oil so the oil does not turn rancid.
5.4Medicines and cosmetics
Medicines are chemicals used to treat or prevent disease. Cosmetics are products applied externally to cleanse, protect or enhance appearance.
Traditional medicines
Obtained from plants or animals without chemical processing. Examples: ginger (removes wind, warms the body), aloe vera (burns and skin diseases), ginseng (builds immunity, lowers blood pressure and cholesterol), tamarind (juice relieves coughs).
Modern medicines
| Type | Function and examples | Side effects and care |
|---|---|---|
| Analgesics | Relieve pain: aspirin, paracetamol, codeine | Aspirin is acidic and can cause stomach ulcers; paracetamol overdose damages the liver; codeine causes drowsiness |
| Antimicrobials | Antibiotics (penicillin, streptomycin) kill bacteria; antiseptics (iodine) for skin; disinfectants (alcohol) for objects | Complete the antibiotic course or bacteria become resistant; penicillin allergy can be fatal |
| Psychotic drugs | Treat psychosis: haloperidol, chlorpromazine | Involuntary body movements, stiffness, shakes |
| Anti-allergies | Relieve runny nose and itching: antihistamines | Drowsiness, dry mouth, blurred vision |
| Corticosteroids | Reduce swelling and inflammation (asthma, arthritis): prednisolone | Long-term use: moon face, high blood pressure, high blood sugar |
Medicines must be taken as prescribed. Misuse or abuse can be harmful, for traditional medicines too. Modern medicines pass clinical trials; many traditional ones lack data to prove effectiveness or the correct dose. The NPRA supervises drug safety and quality control of cosmetics.
Cosmetics
- Basic ingredients: water (solvent), emulsifiers, thickeners, dyes, moisturisers, preservatives, fragrances.
- Types: makeup (lipstick, powder), treatment (creams, moisturisers) and fragrances (perfume, deodorant).
- Harmful chemicals sometimes added illegally: mercury (kidney and nerve damage), hydroquinone (hypersensitive skin), betamethasone valerate, tretinoin (redness, peeling). Check that products are registered with NPRA.
- Homemade cosmetics are cheap and free of harmful chemicals; commercial ones may have side effects or misleading claims.
Aida has a headache. Which type of modern medicine is suitable, and give one example?
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An analgesic, e.g. paracetamol.
5.5Nanotechnology in industry
Nanoscience is the study of substances at the nanoscale, 1 nm to 100 nm. Nanotechnology is the development of substances or devices using the properties of nanoparticles. (1 nm = 10−9 m)
Textbook crop: Chemistry Form 5 (DLP), Figure 5.18, p. 187.
Applications
| Field | Examples |
|---|---|
| Semiconductors and electronics | Smaller, more efficient chips; highly conductive wiring |
| Energy | More efficient solar cells, long-lasting batteries |
| Textile | Water-, fire- and dirt-resistant, anti-wrinkle, UV-protective fabric |
| Medical | Sensitive testing devices, better drug delivery |
| Agriculture | More effective pesticides and fertilisers |
| Food | Nanoscale additives, anti-microbial packaging |
| Cosmetics | Particles penetrate skin easily and coat the surface evenly |
Graphene
Graphene is a single sheet of carbon atoms, an allotrope of carbon (with diamond and graphite). It was isolated in 2004 by Andre Geim and Konstantin Novoselov (Nobel Prize 2010).
- Physical properties: strong and hard, transparent, elastic, impermeable, good conductor of heat and electricity (very low electrical resistance).
- Chemical properties: burns at a lower temperature than graphite; the most reactive carbon allotrope; graphene oxide is used as a catalyst.
- Uses: electronics, polymer composites (strength), sensors (high surface area), membranes for water filtration, biomedicine, energy storage.
State the size range of nanoparticles and give one reason graphene suits polymer composites.
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1 to 100 nm. Graphene has high mechanical strength, so it strengthens polymer composites.
5.6Green Technology in industrial waste management
Green Technology is technology or application developed to minimise the negative effects of harmful human activities. Malaysia introduced the National Green Technology Policy in 2009; GreenTech Malaysia promotes it.
Sectors: energy supply (solar, hydro, wind), transportation (alternative fuels), buildings, waste and wastewater management, agriculture and forestry (compost), industry (energy-efficient tools).
Waste management
Solid waste is collected, sorted and recycled, composted (organic waste), incinerated or sent to landfill. Green Technology is used for composting, recycling, methane recovery and treating leachate (contaminated liquid from water leaching through solid waste).
Industrial wastewater
Industrial wastewater may contain toxic substances such as acrylonitrile, methylbenzene and heavy metals (arsenic, mercury, lead) that decompose poorly, so it needs systematic treatment.
ElectrocoagulationWastewater is the electrolyte and carbon or copper electrodes are used. Pollutants form flocs, which settle and are removed as sludge. The sludge becomes fertiliser or is disposed of properly; treated water is reused for irrigation or discharged as effluent.
Steps: pump in wastewater, screen solid waste, electrocoagulation, settling, collect sludge, further treatment, discharge effluent.
Importance
Cleaner energy, more effective waste management, slower global warming (lower greenhouse gas and carbon footprint), innovation, better living standards and new jobs.
Why must landfill leachate be treated before it is released?
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It contains hazardous chemicals that would pollute water sources and harm health.