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.
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.
Question types you will see
Each type: how to recognise it, the method step by step, and one question to try.
Ore → metal matching
'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.
each metal's name echoes in its ore except the classic traps, so recall by pair, not by logic.
Cinnabar is an ore of —
Show solutionHide solution
Mercury (HgS). Heating cinnabar in air gives mercury vapour + SO₂ — an extraction by roasting alone.
Alloy → composition
'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.
Brass is an alloy of —
Show solutionHide solution
Copper and zinc. Bronze is the copper–tin one; german silver is copper + zinc + nickel.
Metallurgy steps and processes
'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).
Roasting is done for —
Show solutionHide solution
Sulphide ores in excess air — it converts them to oxides, driving off SO₂. Calcination is the carbonate-ore, limited-air version.
Reactivity series consequences
'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.
Which metal will NOT liberate hydrogen from dilute hydrochloric acid?
Show solutionHide solution
Copper — it lies below hydrogen in the reactivity series (so do silver, gold, mercury).
Corrosion and its prevention
'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.
A green coating slowly appears on a copper vessel left in damp air. It is —
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Basic copper carbonate — copper reacts slowly with moist air (O₂, H₂O and CO₂). Silver instead turns black with silver sulphide.
Metal/non-metal properties and exceptions
'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.
Which non-metal conducts electricity?
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Graphite — free electrons between its carbon layers carry current, so it serves as electrodes.
Formula sheet
22 ct ≈ 91.67%
Shortcuts that save time
Potassium, Sodium, Calcium, Magnesium, Aluminium, Zinc, Iron, Lead, Hydrogen, Copper, Mercury, Silver, Gold.
Br-a-ss has Zinc (think 'brass band with Zing'); Bronze has Tin (bronze medal — 'third'/tin). Both are copper-based.
Bronze is an alloy of?
Show solutionHide solution
Copper and tin.
Mistakes to avoid
Where most students lose marks on this subtopic.
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.
Quick revision
Read this the night before the exam.
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.
Practice: 19 questions
Sets of 10, mixed across the question types above. Every answer has a step-by-step explanation.
Topic test · 10 questions
Suggested time 3 min · wrong answers go to your mistake notebook automatically.