Everyday Chemistry
Subject: General Science — Chemistry | Topic: Everyday Chemistry Exam: AP Group 2 (APPSC) | Sources: NCERT Class X, Lucent's GS
Introduction
Everyday chemistry covers carbon compounds, soaps and detergents, polymers, fuels, and chemicals in food and medicine. APPSC frequently tests practical knowledge — LPG composition, antibiotics, preservatives, and plastic types.
Carbon and Its Compounds
- Carbon: atomic number 6, valency 4, forms 4 covalent bonds. Basis of organic chemistry.
- Catenation: Carbon's ability to bond with other carbon atoms (chains, branches, rings).
- Hydrocarbons: Compounds of C and H only.
- Saturated (alkanes): Single bonds. CₙH₂ₙ₊₂. Methane (CH₄), Ethane (C₂H₆).
- Unsaturated (alkenes/alkynes): Double/triple bonds. More reactive.
- Homologous series: Family with same general formula, differing by −CH₂−.
Important Carbon Compounds
| Compound | Formula | Details |
|---|---|---|
| Methane | CH₄ | Main component of natural gas and biogas; greenhouse gas |
| Ethanol | C₂H₅OH | Drinking alcohol; solvent, fuel, antiseptic. Denatured alcohol = ethanol + methanol (poisonous) |
| Ethanoic acid | CH₃COOH | Acetic acid. 5-8% solution = vinegar. Pure form = glacial acetic acid |
Soaps and Detergents
- Soap: Sodium/potassium salt of long-chain fatty acids (e.g., sodium stearate C₁₇H₃₅COONa).
- Soap molecule: hydrophilic head (water-loving) + hydrophobic tail (oil-loving).
- Micelle formation: Soap surrounds oil droplets — tails inward, heads outward — washes away in water.
- Soap does NOT lather in hard water (Ca²⁺/Mg²⁺ form insoluble scum).
- Detergents: Synthetic sulphonate salts. Work in hard water. Less biodegradable than soaps.
Chemical Reactions in Daily Life
| Reaction Type | Definition | Examples |
|---|---|---|
| Combustion | Burning in O₂ → heat + light | LPG, wood, candle |
| Oxidation | Gain of O₂ or loss of H₂ | Rusting |
| Reduction | Loss of O₂ or gain of H₂ | Smelting |
| Exothermic | Releases heat | Combustion, neutralisation, respiration |
| Endothermic | Absorbs heat | Photosynthesis, dissolving NH₄Cl in water |
Chemicals in Food and Medicine
| Category | Examples | Notes |
|---|---|---|
| Preservatives | Salt, sugar, vinegar, sodium benzoate | Prevent spoilage |
| Antioxidants | BHA, BHT, Vitamin C, Vitamin E | Prevent oxidation/rancidity |
| Artificial sweeteners | Saccharin, Aspartame, Sucralose | Zero calories |
| Baking powder | NaHCO₃ + tartaric acid | CO₂ released on heating → fluffy bread |
| Analgesics | Aspirin, Paracetamol, Ibuprofen | Pain killers |
| Antibiotics | Penicillin (Fleming, 1928), Streptomycin | Kill bacteria, NOT viruses |
| Antiseptics | Dettol, Savlon, tincture of iodine | On living tissue |
| Disinfectants | Phenol, bleach | On non-living surfaces |
| Antacids | Milk of magnesia, sodium bicarbonate | Neutralise excess stomach acid |
Polymers
| Type | Property | Examples |
|---|---|---|
| Natural | — | Cellulose, starch, proteins, rubber, silk, wool, DNA |
| Thermoplastics | Soften on heating, can be remoulded | Polythene (bags), PVC (pipes), Nylon (textiles) |
| Thermosetting | Set permanently, cannot be remoulded | Bakelite (switches), Melamine |
- Teflon: Non-stick coating. Nylon: First fully synthetic fibre.
- Plastic is non-biodegradable — major environmental pollutant.
Fuels
| Fuel | Composition | Use |
|---|---|---|
| LPG | Mainly butane (C₄H₁₀). Ethyl mercaptan added for leak detection | Cooking |
| CNG | Mainly methane (CH₄). Cleaner than petrol/diesel | Vehicles |
| Petroleum fractions | LPG → Petrol → Kerosene → Diesel → Lubricating oil → Paraffin wax → Bitumen | Fractional distillation |
Construction and Glass
| Material | Composition | Uses |
|---|---|---|
| Cement | Calcium silicates + aluminates | Construction |
| Concrete | Cement + sand + gravel + water. RCC = with steel bars | Structures |
| Soda-lime glass | SiO₂ + Na₂CO₃ + CaCO₃ | Windows |
| Borosilicate/Pyrex | Heat-resistant glass | Lab equipment |
Water Treatment
- Chlorination: Cl₂ or bleaching powder kills germs.
- Alum: Coagulation — settles suspended impurities.
- Boiling, UV, RO also purify water.
Likely Exam Questions
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The main component of LPG is: Ans: Butane (C₄H₁₀)
-
The first antibiotic discovered was: Ans: Penicillin (by Alexander Fleming, 1928)
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Soap does not lather in hard water because: Ans: Ca²⁺/Mg²⁺ ions react with soap to form insoluble scum
-
Baking powder contains: Ans: Sodium bicarbonate (NaHCO₃) + tartaric acid
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A thermosetting plastic used in electrical switches is: Ans: Bakelite
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Ethyl mercaptan is added to LPG for: Ans: Leak detection (it gives LPG its distinctive smell)
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The chemical name of vinegar is: Ans: Acetic acid (CH₃COOH), 5-8% solution
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CNG mainly contains: Ans: Methane (CH₄)
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Teflon is used for: Ans: Non-stick coating on cookware
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Alum is used in water purification for: Ans: Coagulation (settling suspended impurities)