Chemistry
🔒 Log in to trackMetals, ores, metallurgy and alloys
🔒 Log in to trackOres
| Metal | Main ore(s) |
|---|---|
| Aluminium | Bauxite (Al₂O₃·2H₂O) |
| Iron | Haematite (Fe₂O₃), magnetite (Fe₃O₄), siderite |
| Copper | Copper pyrites / chalcopyrite, malachite, cuprite |
| Zinc | Zinc blende (ZnS), calamine |
| Lead | Galena (PbS) |
| Mercury | Cinnabar (HgS) |
| Tin | Cassiterite (SnO₂) |
| Uranium | Pitchblende |
| Silver | Argentite |
| Sodium | Rock salt |
| Magnesium | Magnesite, dolomite, carnallite |
| Calcium | Limestone, gypsum |
Metallurgy steps
- Concentration — froth flotation for sulphide ores (pine oil used); magnetic separation; gravity separation.
- Calcination — heating carbonate ores in limited air; roasting — heating sulphide ores in excess air.
- Reduction — with carbon (iron in a blast furnace) or by electrolysis (aluminium — Hall–Héroult process; sodium, potassium).
- Refining — electrolytic refining (copper), with the impure metal as the anode.
Reactivity series
K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Hg > Ag > Au
- Metals above hydrogen give H₂ with dilute acids; copper, silver and gold do not.
- Sodium and potassium are stored under kerosene (they react violently with air and water). White phosphorus is stored under water (it catches fire in air).
- Gold and platinum are noble metals — very unreactive.
Alloys
| Alloy | Composition | Use |
|---|---|---|
| Brass | Copper + Zinc | Utensils, fittings |
| Bronze | Copper + Tin | Statues, medals, bells |
| Bell metal | Copper + Tin (higher tin) | Bells |
| Gun metal | Copper + Tin + Zinc | Gears, castings |
| German silver | Copper + Zinc + Nickel (no silver) | Utensils, decorative items |
| Solder | Lead + Tin | Joining electrical wires (low melting point) |
| Stainless steel | Iron + Chromium + Nickel + Carbon | Cutlery, utensils (does not rust) |
| Duralumin | Aluminium + Copper + Magnesium + Manganese | Aircraft bodies |
| Magnalium | Aluminium + Magnesium | Light instruments |
| Nichrome | Nickel + Chromium | Heater coils |
| Amalgam | Any metal + Mercury | Dental fillings (silver–tin amalgam) |
Gold purity
- 24 carat = pure gold. Purity % = (carat ÷ 24) × 100, so 22 carat ≈ 91.67%, 18 carat = 75%.
- Jewellery gold is alloyed with copper or silver to make it harder.
Detailed notes
Metals, non-metals and the exceptions
Metals are lustrous, malleable, ductile, good conductors of heat and electricity, and sonorous. Non-metals are mostly dull, brittle and insulating. The exceptions carry the marks: mercury is a liquid metal; sodium and potassium are soft metals cut with a knife; graphite (a non-metal) conducts electricity; iodine is a lustrous non-metal; diamond, the hardest natural substance, is a non-metal.
Ore → metal
| Metal | Main ore(s) |
|---|---|
| Aluminium | Bauxite |
| Iron | Haematite, magnetite, siderite |
| Copper | Copper pyrites (chalcopyrite), malachite |
| Zinc | Zinc blende (ZnS), calamine |
| Lead | Galena (PbS) |
| Mercury | Cinnabar (HgS) |
| Tin | Cassiterite |
| Uranium | Pitchblende |
| Sodium | Rock salt |
| Calcium | Limestone, gypsum |
Metallurgy — the four steps
- Concentration of the ore: froth flotation for sulphide ores (powdered ore + pine oil + air — sulphide sticks to the froth); magnetic separation for magnetic ores; gravity separation.
- Conversion to oxide: calcination = heat a carbonate ore in limited air; roasting = heat a sulphide ore in excess air. Memory hook: Calcination–Carbonate, roasting–sulphide.
- Reduction to metal: carbon/CO in the blast furnace (iron); electrolysis for very reactive metals — aluminium (Hall–Héroult process), sodium, magnesium.
- Refining: electrolytic refining — impure metal at the anode dissolves and pure metal deposits on the cathode (used for copper).
Reactivity series and its uses
K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Hg > Ag > Au.
- Metals above hydrogen release H₂ from dilute acids; copper, silver, gold do not.
- Na and K are stored under kerosene (they catch fire in moist air); Ca and Mg need care too.
- Metals below hydrogen occur free in nature (gold, platinum).
- A more reactive metal displaces a less reactive one from its salt solution (iron nail in copper sulphate turns the solution green).
Corrosion and its prevention
Rusting needs both air and moisture; rust is hydrated iron oxide (Fe₂O₃·xH₂O). Protection: galvanisation (coating with zinc — even the zinc's position above iron in the reactivity series lets it sacrifice itself), painting, greasing, electroplating, and alloying to stainless steel. Silver tarnishes black (Ag₂S with sulphur in air); copper grows a green patina (basic copper carbonate); aluminium protects itself with a thin oxide film (made thicker by anodising).
Alloys — composition list
| Alloy | Composition | Use / note |
|---|---|---|
| Brass | Cu + Zn | Utensils, decor; not Cu+Sn |
| Bronze | Cu + Sn | Statues, bells |
| Bell metal | Cu + Sn (more Sn) | Bells, gongs |
| Stainless steel | Fe + Cr + Ni (+ C) | Cutlery; rust-free |
| Duralumin | Al + Cu (+ Mg, Mn) | Aircraft — light and strong |
| Solder | Pb + Sn | Joining wires; low melting point |
| German silver | Cu + Zn + Ni | Cutlery (no real silver) |
| Nichrome | Ni + Cr (+ Fe) | Heating coils — high resistance |
| Invar | Fe + Ni | Very low expansion — pendulums, tapes |
| Amalgam | Any metal + mercury | Dental fillings (except iron/platinum) |
Gold purity: 24 carat = pure; 22 carat gold = 22/24 ≈ 91.6% gold.
Quick revision
- Calcination–carbonate, roasting–sulphide; froth flotation–sulphide ores; electrolysis–Al, Na.
- Al→bauxite, Fe→haematite, Hg→cinnabar, Zn→zinc blende, Pb→galena, Sn→cassiterite, U→pitchblende.
- K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au; Cu/Ag/Au give no H₂ with dilute acid.
- Brass Cu+Zn, bronze Cu+Sn, solder Pb+Sn, duralumin Al+Cu, stainless Fe+Cr+Ni, nichrome Ni+Cr.
- Rusting = air + moisture; galvanising = zinc coat; amalgam = metal + mercury; 24 carat pure.
Types of questions asked
Every way this subtopic shows up in exams — how to recognise it, the formula or logic to use, and a solved example.
Type 1: Ore → metal matchingvery common3 practice Q
'Bauxite is the ore of…', 'cinnabar / galena / pitchblende is an ore of which metal', match-the-column of ores and metals.
- Headline pairs: bauxite–aluminium, haematite–iron, cinnabar–mercury, galena–lead, zinc blende–zinc, cassiterite–tin, copper pyrites–copper, pitchblende–uranium, rock salt–sodium.
- Trap: calamine is also zinc (with zinc blende); magnetite and siderite also iron.
- In match-the-columns, fix the surest pair first (bauxite–Al) and chain the rest. Why: each metal's name echoes in its ore except the classic traps, so recall by pair, not by logic.
Example: Cinnabar is an ore of —
Mercury (HgS). Heating cinnabar in air gives mercury vapour + SO₂ — an extraction by roasting alone.
Type 2: Alloy → compositionvery common3 practice Q
'Brass is an alloy of…', 'which alloy contains tin', 'stainless steel is made by adding…to iron', distinguish brass from bronze.
- Copper family: brass = Cu + Zn; bronze = Cu + Sn; bell metal = Cu + Sn (tin-rich); german silver = Cu + Zn + Ni.
- Iron family: stainless steel = Fe + Cr + Ni; invar = Fe + Ni.
- Light metals: duralumin = Al + Cu; magnalium = Al + Mg; solder = Pb + Sn; nichrome = Ni + Cr; amalgam = metal + Hg.
- The classic trap: brass is Zn, bronze is Sn.
Example: Brass is an alloy of —
Copper and zinc. Bronze is the copper–tin one; german silver is copper + zinc + nickel.
Type 3: Metallurgy steps and processescommon3 practice Q
'Roasting is used for … ores', 'calcination vs roasting', 'froth flotation separates…', 'which metal is extracted by electrolysis', 'Hall–Héroult process is for…'.
- Concentration: froth flotation for sulphide ores (pine oil); gravity/magnetic separation.
- Oxide conversion: calcination = carbonate ore, limited air; roasting = sulphide ore, excess air.
- Reduction: carbon in the blast furnace (Fe); electrolysis for Al, Na, Mg (Hall–Héroult for aluminium).
- Refining: electrolytic — impure anode, pure cathode (copper).
Example: Roasting is done for —
Sulphide ores in excess air — it converts them to oxides, driving off SO₂. Calcination is the carbonate-ore, limited-air version.
Type 4: Reactivity series consequencescommon3 practice Q
'Which metal does not give H₂ with dilute acid', 'why is sodium stored in kerosene', 'which metal occurs free in nature', displacement-reaction questions.
- Order: K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au.
- Above H → H₂ from dilute acids; Cu/Ag/Au do not react so.
- Top metals (K, Na, Ca) catch fire in moist air → stored under kerosene; bottom metals (Au, Pt) occur free.
- A more reactive metal displaces a less reactive metal from its salt solution.
Example: Which metal will NOT liberate hydrogen from dilute hydrochloric acid?
Copper — it lies below hydrogen in the reactivity series (so do silver, gold, mercury).
Type 5: Corrosion and its preventioncommon2 practice Q
'Rusting requires…', 'galvanisation is coating iron with…', 'green coating on copper / black coating on silver', 'anodising is done on…'.
- Rusting needs both air and moisture; rust is hydrated iron(III) oxide.
- Prevention: galvanisation (zinc coat), painting/oiling, electroplating, anodising (thicker oxide on aluminium), alloying (stainless steel).
- Colour clues: iron–red-brown rust; copper–green basic carbonate; silver–black Ag₂S tarnish.
Example: A green coating slowly appears on a copper vessel left in damp air. It is —
Basic copper carbonate — copper reacts slowly with moist air (O₂, H₂O and CO₂). Silver instead turns black with silver sulphide.
Type 6: Metal/non-metal properties and exceptionscommon2 practice Q
'Which metal is liquid / soft / stored in kerosene', 'which non-metal conducts electricity', 'most ductile metal', carat-purity of gold.
- Exceptions: Hg liquid metal; Na, K soft metals; graphite conducts; iodine lustrous; diamond hard but non-metal.
- Best conductor among metals – silver; most ductile/malleable – gold; highest melting point – tungsten.
- Purity: 24 carat pure; 22 carat ≈ 91.6%; carat also = 200 mg for gems.
Example: Which non-metal conducts electricity?
Graphite — free electrons between its carbon layers carry current, so it serves as electrodes.
Formulas
22 ct ≈ 91.67%
Shortcut tricks
⚡ Reactivity series: 'Please Stop Calling Me A Zebra, I Like Her Calling Me Smart Goat'
Potassium, Sodium, Calcium, Magnesium, Aluminium, Zinc, Iron, Lead, Hydrogen, Copper, Mercury, Silver, Gold.
⚡ Brass vs Bronze
Br-a-ss has Zinc (think 'brass band with Zing'); Bronze has Tin (bronze medal — 'third'/tin). Both are copper-based.
Example: Bronze is an alloy of?
Copper and tin.
Where students lose marks
Believing German silver contains silver — it is copper, zinc and nickel.
Naming haematite as an aluminium ore — it is iron; bauxite is aluminium.
Saying solder has a high melting point — its low melting point is the whole point.
Practice sets — 19 questions
Sets of 10, mixed across the question types above. Each answer comes with a step-by-step explanation.
Topic test · 10 questions
Suggested time 3 min · wrong answers go to your mistake notebook automatically.