NDA Chemistry · Teaching notes
Chemistry in Everyday Life — NDA Chemistry
Chemistry in Everyday Life is a small, pure named-fact recall chapter — about ten PYQs across 2017–2026, almost every one a 'which chemical / which medicine / which gas' single-fact question. There is nothing to derive; the marks go to whoever has memorised the name↔use pairs. The chapter teaches in two movements: (1) Common chemicals and their uses — the household and industrial substances the bank names by use: washing soda, plaster of Paris, potassium permanganate, silver salts in photography, clean fuels and biogas, and the diver's breathing gas; (2) Medicines and health chemistry — the drug classes (antacid, analgesic, antibiotic, antiseptic versus disinfectant), the calcium compound in tooth enamel, and the radioisotope used to treat cancer. Most concepts are reference tables: learn the table, win the marks. The classic traps are antiseptic-versus-disinfectant and analgesic-versus-antipyretic — same-sounding classes, different jobs.
Subtopic notes
Common Chemicals and Their Uses
7 PYQsThe household and industrial substances the NDA names by their use — washing soda, plaster of Paris, potassium permanganate, silver salts in photography, clean fuels, biogas, and the gas divers breathe.
Open note
Medicines and Health Chemistry
3 PYQsThe drug classes the NDA names by their job — antacid, analgesic, antibiotic, antiseptic versus disinfectant — plus the calcium compound in tooth enamel and the radioisotope used to treat cancer.
Open note
PYQ weightage by concept
6 concepts · 10 PYQs — where the marks actually sit, so you know what to drill first
PYQ weightage by concept
6 concepts · 10 PYQs — where the marks actually sit, so you know what to drill first
| Concept | PYQs | Share |
|---|---|---|
| Household chemicals by use | 4 | 40% |
| Clean fuels and biogas | 2 | 20% |
| Gas mixtures for breathing | 1 | 10% |
| Concept | PYQs | Share |
|---|---|---|
| Drug classes by their job | 1 | 10% |
| Radioisotopes and elements in medicine | 1 | 10% |
| Chemistry of the body — bones and teeth | 1 | 10% |
Formula & revision sheet
0 formulas · 6 reference tables · 11 gotchas across all subtopics — the exam-eve cheat-sheet
Formula & revision sheet
0 formulas · 6 reference tables · 11 gotchas across all subtopics — the exam-eve cheat-sheet
Reference tables (3)
Household chemicals by use4 rows
| Substance | Formula | Common use |
|---|---|---|
| Washing soda | Na₂CO₃·10H₂O | Cleaning; softening hard waterQ Washing soda = sodium carbonate (Na₂CO₃). Baking soda is sodium bicarbonate (NaHCO₃) — different substance. |
| Plaster of Paris | CaSO₄·½H₂O | Casts, moulds, blackboard chalkQ Plaster of Paris is CaSO₄·½H₂O (hemihydrate) — NOT CaSO₄·2H₂O. CaSO₄·2H₂O is gypsum. This wrong formula is the bank's favourite 'NOT correct' statement. |
| Potassium permanganate | KMnO₄ | Purifies drinking water (oxidizing agent)Q KMnO₄ purifies water because it is an oxidizing agent — it oxidises (destroys) organic impurities and microbes. |
| Silver bromide | AgBr | Black-and-white photography (light-sensitive)Q Silver halides (AgBr, AgCl) darken in light — used in photographic film. Not a silver oxide or nitrate here. |
Clean fuels and biogas3 rows
| Fuel | Main component | Note |
|---|---|---|
| Clean fuel / LPG | Propane (C₃H₈) with butane | Burns cleanly, little sootQ Propane is the clean-fuel answer; it is a key component of LPG. |
| Biogas (gobar gas) | Methane (CH₄) | From anaerobic decay of organic wasteQ Biogas is MAINLY methane (≈ 50–70%), with carbon dioxide as the next gas. The major constituent is methane. |
| CNG (vehicle fuel) | Methane (CH₄) | Compressed natural gas; cleaner than diesel |
Gas mixtures for breathing2 rows
| Use | Gas mixture | Why |
|---|---|---|
| Deep-sea diving | Oxygen + helium (heliox) | Helium avoids nitrogen narcosis; low density eases breathingQ Divers breathe oxygen + HELIUM — not oxygen + nitrogen. Nitrogen at depth causes narcosis. |
| Hospital / medical use | Oxygen (sometimes with helium or CO₂) | Pure oxygen or controlled mixtures for patients |
Watch out for (6)
- Plaster of Paris is CaSO₄·½H₂O, not CaSO₄·2H₂O→ Household chemicals by use
- Washing soda ≠ baking soda→ Household chemicals by use
- KMnO₄ disinfects by oxidising, not by killing on contact→ Household chemicals by use
- Biogas is mainly methane, not carbon dioxide→ Clean fuels and biogas
- LPG and CNG are different gases→ Clean fuels and biogas
- Divers breathe oxygen + helium, not oxygen + nitrogen→ Gas mixtures for breathing
Reference tables (3)
Drug classes by their job6 rows
| Class | Job | Example |
|---|---|---|
| Antacid | Treats indigestion / acidity | Milk of magnesia, NaHCO₃Q Antacid is the answer for indigestion — it neutralises excess stomach acid. |
| Analgesic | Relieves pain | Aspirin, paracetamol |
| Antipyretic | Reduces fever | Paracetamol |
| Antibiotic | Kills bacteria | Penicillin |
| Antiseptic | Kills microbes on living skin/tissue | Dettol, tincture of iodine Antiseptic is for the BODY (cuts, skin). Disinfectant is for SURFACES (floors). Same idea, different place. |
| Disinfectant | Kills microbes on non-living surfaces | Phenol, chlorine, bleach |
Radioisotopes and elements in medicine4 rows
| Isotope | Medical use |
|---|---|
| Cobalt-60 | Radiotherapy for cancer (gamma rays)Q Cobalt-60 is the cancer-treatment isotope the bank asks for ('cobalt therapy'). |
| Iodine-131 | Thyroid diagnosis and treatment |
| Sodium-24 | Tracing blood circulation |
| Phosphorus-32 | Treating certain blood disorders |
Chemistry of the body — bones and teeth2 rows
| Body part | Main chemical |
|---|---|
| Tooth enamel | Calcium phosphate (hydroxyapatite)Q Tooth enamel = calcium phosphate. Not calcium carbonate or calcium chloride. |
| Bones | Calcium phosphate (with some carbonate) |
Watch out for (5)
- Antiseptic (skin) versus disinfectant (surfaces)→ Drug classes by their job
- Analgesic (pain) versus antipyretic (fever)→ Drug classes by their job
- Antacid treats acidity, not infection→ Drug classes by their job
- Cobalt-60 treats cancer; iodine-131 treats the thyroid→ Radioisotopes and elements in medicine
- Tooth enamel is calcium phosphate, not calcium carbonate→ Chemistry of the body — bones and teeth