CDS Chemistry · Teaching notes
Chemistry in Everyday Life — CDS Chemistry
Chemistry in Everyday Life has 9 past-year questions in CDS General Knowledge, from 2016 (II) to 2026 (I), about one every year. Each one matches a substance to a use: xenon to the camera flash, strontium to red fireworks, barium sulphate to the X-ray meal, tincture of iodine to a fresh wound. There is no method to learn here, only pairs, so the two tables on these pages carry the chapter. The traps are the near misses: barium chloride for barium sulphate, neon for xenon.
Every subtopic, worked example, formula and trap in one printable document — answers shown, ready to share.
Subtopic notes
Elements and Compounds in Everyday Use
6 PYQsWhat magnesium, calcium, strontium, barium and the noble gases do in life and industry, and the everyday uses of carbon dioxide, nitrogen and potassium nitrate.
Antiseptics and the Barium Meal
3 PYQsWhat tincture of iodine is made of, and why insoluble barium sulphate is safe to swallow for an X-ray while soluble barium salts are poisons.
Formula & revision sheet
0 formulas · 4 reference tables · 12 gotchas across all subtopics — the exam-eve cheat-sheet
Formula & revision sheet
0 formulas · 4 reference tables · 12 gotchas across all subtopics — the exam-eve cheat-sheet
Reference tables (2)
Uses of group 2 metals and noble gases6 rows
| Element | Use or property |
|---|---|
| Magnesium | Traps sunlight in chlorophyll |
| Calcium | Controls muscle contraction |
| Strontium | Red colour in flames |
| Barium | Sulphate used to X-ray the alimentary canal |
| Xenon | Bright flash in a photographer's flashgunQ |
| Neon | Red glow in advertising signs |
Everyday uses of carbon dioxide, nitrogen and potassium nitrate4 rows
| Substance | Everyday use |
|---|---|
| Carbon dioxide | Makes soft drinks fizzyQ |
| Sodium hydrogen carbonate + sulphuric acid | Soda-acid fire extinguisher |
| Nitrogen | Flushed into food packets against oxidationQ CDS 2026 (I): this statement and 'tooth decay below pH 5.5' were correct; 'Mg > Fe > Zn' was the wrong one (zinc is above iron). |
| Potassium nitrate | Fertilizer, gunpowder, meat preservativeQ |
Watch out for (6)
- Strontium is red, barium is green→ Uses of group 2 metals and noble gases
- Flash tubes use xenon, not neon→ Uses of group 2 metals and noble gases
- Magnesium, not iron, is in chlorophyll→ Uses of group 2 metals and noble gases
- The extinguisher uses the hydrogen carbonate→ Everyday uses of carbon dioxide, nitrogen and potassium nitrate
- Zinc is above iron→ Everyday uses of carbon dioxide, nitrogen and potassium nitrate
- Soft drinks hold carbon dioxide, not ammonia or phosgene→ Everyday uses of carbon dioxide, nitrogen and potassium nitrate
Reference tables (2)
Tincture of iodine and other antiseptics5 rows
| Component of tincture of iodine | Present? |
|---|---|
| Iodine (dilute) | Yes |
| Potassium iodide | Yes — keeps iodine dissolved |
| Alcohol (ethanol) | Yes |
| Water | Yes |
| Acetone | NoQ |
The barium meal2 rows
| Salt | Soluble? | Safe as an X-ray meal? |
|---|---|---|
| Barium sulphate | No | YesQ |
| Barium chloride | Yes | No — poisonous |
Watch out for (6)
- No acetone in tincture of iodine→ Tincture of iodine and other antiseptics
- The iodine is dilute→ Tincture of iodine and other antiseptics
- An antacid is a base→ Tincture of iodine and other antiseptics
- Antiseptic, not antibiotic→ Tincture of iodine and other antiseptics
- Barium sulphate, not barium chloride→ The barium meal
- It works because barium blocks X-rays→ The barium meal
PYQ weightage by concept
4 concepts · 9 PYQs — where the marks actually sit, so you know what to drill first
PYQ weightage by concept
4 concepts · 9 PYQs — where the marks actually sit, so you know what to drill first
| Concept | PYQs | Share |
|---|---|---|
| Everyday uses of carbon dioxide, nitrogen and potassium nitrate | 4 | 44% |
| Uses of group 2 metals and noble gases | 2 | 22% |
| Concept | PYQs | Share |
|---|---|---|
| Tincture of iodine and other antiseptics | 2 | 22% |
| The barium meal | 1 | 11% |
Test yourself on a real paper
Sit a past CDS paper, timed and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.