NDA Chemistry · Teaching notes
Metals and Non-Metals — NDA Chemistry
Metals and Non-Metals is a compact recall chapter — about 17 PYQs across 2017–2026, almost every one a 'which is correct' or 'which is NOT' about reactivity, an ore, corrosion, or an alloy. There is no derivation to do; the marks go to whoever has the reactivity series and the ore/alloy tables memorised. The chapter teaches in four movements, building from general properties up to applications: (1) Reactivity series and reactions with water — the order of metals from most to least reactive, which metals float, which react with cold water versus steam, and the alkali-metal melting-point trend; (2) Extraction of metals and ores — the common ores and the reduction method each metal needs (carbon reduction, electrolysis, or none for native metals); (3) Corrosion and its prevention — why iron rusts, why copper turns green, and how galvanization and sacrificial protection work; (4) Alloys and their composition — what brass, bronze, steel, amalgam, stainless steel and NaK are made of. Most concepts are reference tables: learn the table, win the marks.
Subtopic notes
Reactivity Series and Reactions with Water
6 PYQsMetals ranked from most reactive (potassium) to least reactive (gold), and how each one behaves toward cold water, hot water and steam.
Open note
Extraction of Metals and Ores
2 PYQsThe naturally occurring ores of common metals and the reduction method each metal needs — carbon reduction, electrolysis, or none for native metals.
Open note
Corrosion and Its Prevention
5 PYQsWhy metals are eaten away by air and moisture — iron rusting, copper turning green — and how galvanization and sacrificial protection stop it.
Open note
Alloys and Their Composition
4 PYQsAlloys are solid mixtures of a metal with one or more other elements — brass, bronze, steel, amalgam — engineered to beat the pure metal on strength, hardness or corrosion resistance.
Open note
PYQ weightage by concept
9 concepts · 17 PYQs — where the marks actually sit, so you know what to drill first
PYQ weightage by concept
9 concepts · 17 PYQs — where the marks actually sit, so you know what to drill first
| Concept | PYQs | Share |
|---|---|---|
| Reactions with water and alkali-metal trends | 5 | 29% |
| The reactivity series — order of metals | 1 | 6% |
| Metals versus non-metals — the property contrastfoundation | — | — |
| Concept | PYQs | Share |
|---|---|---|
| Common ores and their metals | 1 | 6% |
| Extraction method versus reactivity | 1 | 6% |
| Concept | PYQs | Share |
|---|---|---|
| Preventing corrosion — galvanization and sacrificial protection | 3 | 18% |
| Corrosion of common metals | 2 | 12% |
| Concept | PYQs | Share |
|---|---|---|
| Common alloys and their composition | 3 | 18% |
| Special-purpose alloys | 1 | 6% |
Formula & revision sheet
0 formulas · 9 reference tables · 11 gotchas across all subtopics — the exam-eve cheat-sheet
Formula & revision sheet
0 formulas · 9 reference tables · 11 gotchas across all subtopics — the exam-eve cheat-sheet
Reference tables (3)
Metals versus non-metals — the property contrast5 rows
| Property | Metals | Non-metals |
|---|---|---|
| Electron behaviour | Lose electrons (electropositive) | Gain/share electrons (electronegative) |
| Appearance | Lustrous (shiny) | Dull (except graphite, iodine) |
| Malleability | Malleable and ductile | Brittle when solid |
| Conductivity | Good conductors | Poor conductors (except graphite) |
| Nature of oxide | Basic | Acidic Metal oxide + water → base; non-metal oxide + water → acid. This is a common 'which statement is correct' test. |
The reactivity series — order of metals3 rows
| Reactivity | Metals (in order) |
|---|---|
| Most reactive | Potassium (K), Sodium (Na), Calcium (Ca) |
| Moderately reactive | Magnesium (Mg), Aluminium (Al), Zinc (Zn), Iron (Fe) |
| Least reactive | Copper (Cu), Mercury (Hg), Silver (Ag), Gold (Au) |
Reactions with water and alkali-metal trends5 rows
| Metal | Reacts with water? | Note |
|---|---|---|
| Potassium / Sodium | Yes, with cold water | Float and react vigorously (less dense than water) Both K and Na float on water; potassium reacts even more vigorously than sodium. |
| Calcium | Yes, with cold water | Reacts steadily, releasing H₂ |
| Magnesium | No (cold); yes with steam | Does NOT react with cold water |
| Iron | No (cold); slow with steam | Does NOT liberate H₂ from cold water |
| Copper | No | Below hydrogen — does not react with water |
Watch out for (4)
- Oxide nature is reversed for non-metals→ Metals versus non-metals — the property contrast
- Iron beats copper, copper beats silver→ The reactivity series — order of metals
- Magnesium and iron do NOT react with cold water→ Reactions with water and alkali-metal trends
- Melting point falls DOWN the alkali group→ Reactions with water and alkali-metal trends
Reference tables (2)
Common ores and their metals6 rows
| Ore | Formula | Metal |
|---|---|---|
| Cinnabar | HgS | Mercury Cinnabar is the ore the bank tests most — it gives mercury. |
| Bauxite | Al₂O₃·2H₂O | Aluminium |
| Haematite | Fe₂O₃ | Iron |
| Zinc blende | ZnS | Zinc |
| Copper pyrites | CuFeS₂ | Copper |
| Galena | PbS | Lead |
Extraction method versus reactivity3 rows
| Reactivity band | Extraction method | Example |
|---|---|---|
| Most reactive (K, Na, Ca, Mg, Al) | Electrolysis of molten ore | Aluminium by electrolysis Carbon CANNOT reduce these — they bind oxygen too strongly. Aluminium is the classic 'needs electrolysis' answer. |
| Moderate (Zn, Fe, Pb, Cu) | Reduction with carbon (coke) | ZnO + C → Zn + CO |
| Least reactive (Ag, Au) | Found native; no reduction | Gold occurs as free metal |
Watch out for (2)
- Cinnabar is mercury, not copper→ Common ores and their metals
- Aluminium needs electrolysis, not carbon→ Extraction method versus reactivity
Reference tables (2)
Corrosion of common metals4 rows
| Metal | Corrosion product | Colour / behaviour |
|---|---|---|
| Iron | Hydrated iron(III) oxide (rust) | Reddish-brown; flakes off — corrodes rapidly Of the common metals, iron corrodes the fastest — its rust flakes away and exposes fresh metal. |
| Copper | Basic copper carbonate | Green coat (patina) in moist air The green coat on old copper is basic copper carbonate, NOT copper oxide. |
| Aluminium | Aluminium oxide | Thin, protective layer — stops further attack |
| Silver | Silver sulphide | Black tarnish in sulphur-containing air |
Preventing corrosion — galvanization and sacrificial protection4 rows
| Method | What is applied | Why it works |
|---|---|---|
| Galvanization | Thin layer of zinc | Zinc is more reactive — sacrifices itself to protect iron Zinc protects iron even when scratched because it is more electropositive than iron (sacrificial protection). |
| Painting / oiling | Paint or grease film | Keeps air and moisture off the metal |
| Electroplating | Tin or chromium layer | Inert coating barrier |
| Alloying | Mix with Cr, Ni (stainless steel) | Forms a corrosion-resistant alloy |
Watch out for (2)
- Copper goes green, iron goes brown→ Corrosion of common metals
- Zinc protects because it is MORE reactive→ Preventing corrosion — galvanization and sacrificial protection
Reference tables (2)
Common alloys and their composition6 rows
| Alloy | Composition | Note |
|---|---|---|
| Brass | Copper + Zinc | Both metals |
| Bronze | Copper + Tin | Cu + Sn — the bank's favourite composition question |
| Steel | Iron + Carbon | Carbon is a non-metal — the 'alloy with a non-metal' answer Steel is the alloy that contains a NON-METAL (carbon). Brass, bronze and amalgam are metal-only. |
| Stainless steel | Iron + Chromium + Nickel (+ C) | Tin is NOT an essential component Essential components of stainless steel are Fe, Cr and Ni — tin is the odd one out. |
| Amalgam | Mercury + another metal | Mercury-based alloy |
| Solder | Lead + Tin | Low-melting joining alloy |
Special-purpose alloys4 rows
| Alloy | Composition | Special use |
|---|---|---|
| NaK | Sodium + Potassium | Coolant / heat transfer in nuclear reactors Potassium is alloyed with sodium (NaK) to transfer heat in nuclear reactors. |
| Nichrome | Nickel + Chromium | Heating elements (high resistance) |
| Magnalium | Aluminium + Magnesium | Light, strong structural parts |
| Type metal | Lead + Tin + Antimony | Printing type |
Watch out for (3)
- Brass vs bronze — don't swap zinc and tin→ Common alloys and their composition
- Tin is not in stainless steel→ Common alloys and their composition
- NaK coolant uses potassium, not calcium→ Special-purpose alloys