Metals and Non-Metals — Class 10 Physical Science
1. Physical Properties — Comparison
| Property | Metals | Non-Metals |
|---|---|---|
| Lustre | Shiny (lustrous) | Dull (except iodine — shiny, graphite — shiny) |
| Malleability | Malleable (beaten into thin sheets) | NOT malleable (brittle) |
| Ductility | Ductile (drawn into wires) | NOT ductile |
| Conduction of heat | GOOD conductors | POOR conductors (except graphite) |
| Conduction of electricity | GOOD conductors | POOR conductors (except graphite — good conductor) |
| State at room temp | SOLID (except mercury — liquid) | SOLID, LIQUID (bromine), or GAS (oxygen, nitrogen) |
| Sonority | Sonorous (ringing sound when struck) | NOT sonorous |
| Density | Usually HIGH | Usually LOW |
'Exceptions are key to exam MCQs: Mercury is a liquid metal. Sodium can be cut with a knife (soft). Graphite is a non-metal that conducts electricity. Iodine is a non-metal with lustre.'
2. Chemical Properties of Metals
Reaction with Oxygen — Formation of Metal Oxides
Metal + Oxygen → Metal Oxide (basic in nature). 2Cu + O₂ → 2CuO (copper oxide — black). 4Al + 3O₂ → 2Al₂O₃ (aluminium oxide — white). 2Mg + O₂ → 2MgO (magnesium oxide — white, dazzling flame).
Nature of metal oxides: MOST metal oxides are BASIC. They turn red litmus BLUE. Soluble metal oxides (Na₂O, K₂O, CaO, MgO) dissolve in water to form ALKALIS: Na₂O + H₂O → 2NaOH. Amphoteric oxides: Some metal oxides react with BOTH acids and bases. Examples: Al₂O₃, ZnO. Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O. Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O.
Reactivity Series of Metals
K > Na > Ca > Mg > Al > Zn > Fe > Pb > [H] > Cu > Hg > Ag > Au > Pt. 'Please Stop Calling Me A Zebra In The Library Cows Munching Silently And Politely.' Metals ABOVE hydrogen displace it from acids. Metals BELOW hydrogen do NOT.
Reaction with Water
- K, Na: React VIOLENTLY with COLD water. 2K + 2H₂O → 2KOH + H₂↑ + HEAT (hydrogen may CATCH FIRE).
- Ca: Reacts with cold water (less violent). Ca + 2H₂O → Ca(OH)₂ + H₂↑.
- Mg: Reacts with HOT water/STEAM. Mg + H₂O → MgO + H₂↑.
- Al, Zn, Fe: React with STEAM only. 3Fe + 4H₂O → Fe₃O₄ + 4H₂↑.
- Cu, Ag, Au, Pt: Do NOT react with water at all.
Reaction with Acids
Metal + Dilute Acid → Salt + Hydrogen. Zn + 2HCl → ZnCl₂ + H₂↑. Fe + H₂SO₄ → FeSO₄ + H₂↑. Cu + HCl → NO REACTION (Cu is below hydrogen in reactivity series).
Reaction with Salt Solutions — Displacement
A MORE reactive metal DISPLACES a LESS reactive metal from its salt solution. Fe + CuSO₄ → FeSO₄ + Cu (blue colour of CuSO₄ fades, reddish-brown copper deposited). Zn + CuSO₄ → ZnSO₄ + Cu. Cu + FeSO₄ → NO REACTION (Cu is less reactive than Fe).
3. Chemical Properties of Non-Metals
Reaction with Oxygen — Formation of Non-Metallic Oxides
C + O₂ → CO₂. S + O₂ → SO₂. Non-metallic oxides are ACIDIC in nature. They turn blue litmus RED. Dissolve in water to form ACIDS: CO₂ + H₂O → H₂CO₃ (carbonic acid). SO₂ + H₂O → H₂SO₃ (sulphurous acid).
Reaction with Hydrogen
Non-metals form covalent hydrides: H₂ + Cl₂ → 2HCl (hydrogen chloride). N₂ + 3H₂ → 2NH₃ (ammonia).
Reaction with Chlorine
Non-metals form covalent chlorides. P₄ + 6Cl₂ → 4PCl₃.
4. Extraction of Metals
Metals are found in the Earth's crust as MINERALS. A mineral from which a metal can be PROFITABLY extracted is called an ORE.
Steps in Extraction
- Concentration (removal of gangue/impurities) — Froth flotation, magnetic separation.
- Conversion to oxide — Roasting (heating in air, for sulphide ores): 2ZnS + 3O₂ → 2ZnO + 2SO₂. Calcination (heating in absence of air, for carbonate ores): ZnCO₃ → ZnO + CO₂.
- Reduction to metal — Using carbon (for Zn, Fe, Pb, Cu): ZnO + C → Zn + CO. Using electrolysis (for K, Na, Ca, Mg, Al — highly reactive).
- Refining — Electrolytic refining for pure metal.
Extraction Based on Reactivity
| Reactivity Zone | Metals | Extraction Method |
|---|---|---|
| High (top) | K, Na, Ca, Mg, Al | ELECTROLYSIS of molten ore |
| Middle | Zn, Fe, Pb, Cu | ROASTING/CALCINATION + reduction with carbon |
| Low (bottom) | Hg, Ag, Au | Found in native state or heating sulphide ore |
5. Corrosion
The SLOW DETERIORATION of metals due to reaction with moisture, air, acids, etc. Rusting of Iron: Fe + O₂ + H₂O → Fe₂O₃·xH₂O (rust — hydrated ferric oxide). Conditions for rusting: BOTH water AND oxygen.
Corrosion of Copper: Green coating — basic copper carbonate (CuCO₃·Cu(OH)₂). Corrosion of Silver: Black coating — silver sulphide (Ag₂S). Corrosion of Aluminium: Al₂O₃ forms a PROTECTIVE layer — prevents further corrosion.
Prevention of Corrosion
- Painting/Greasing/Oiling: Creates a BARRIER between metal and air/moisture.
- Galvanisation: Coating iron with ZINC (sacrificial — Zn corrodes instead of Fe).
- Alloying: Adding other elements (stainless steel = Fe + Cr + Ni).
- Electroplating: Coating with less reactive metal (Cr plating on iron).
- Sacrificial protection: Attaching a more reactive metal (Mg, Zn) blocks to ship hulls.
6. Alloys
An ALLOY is a homogeneous MIXTURE of two or more metals (or metal + non-metal). Properties differ from constituent metals. Brass: Cu + Zn (harder than pure Cu, used for utensils/musical instruments). Bronze: Cu + Sn (statues, coins). Solder: Pb + Sn (low melting point — used for joining electrical wires). Stainless Steel: Fe + Cr + Ni (resists corrosion — utensils, surgical instruments). Amalgam: Hg + any other metal (dental fillings).
7. Ionic vs Covalent Bonding (Context)
Metals and non-metals form IONIC BONDS (transfer of electrons): Na → Na⁺ + e⁻. Cl + e⁻ → Cl⁻. Na⁺ + Cl⁻ → NaCl (ionic compound). Non-metal + non-metal form COVALENT BONDS (sharing of electrons): Cl· + ·Cl → Cl−Cl.
8. Common Mistakes
- 'All metal oxides are basic': Al₂O₃ and ZnO are AMPHOTERIC — react with both acids and bases.
- 'All metals react with acids': Cu, Ag, Au, Pt do NOT react with dilute HCl or H₂SO₄ (below hydrogen).
- 'Graphite is a metal': It's a non-metal — despite conducting electricity and being shiny.
- 'Rusting only requires water': BOTH water AND oxygen are needed. Iron in dry air or pure water (without dissolved O₂) does NOT rust.
9. AP Exam Focus
| Topic | Marks |
|---|---|
| Properties of metals vs non-metals | 3-4 |
| Reactivity series and displacement | 4-5 |
| Extraction of metals | 3-4 |
| Corrosion and prevention | 3-4 |
AP Context
'Visakhapatnam Steel Plant (Vizag Steel) is one of India's major steel producers — the process of extracting iron from its ore and alloying it to make steel is a practical application of this entire chapter. The corrosion of iron structures in coastal Andhra (high humidity + salt spray from the Bay of Bengal) makes rust prevention a critical local industry.'
Quick Self-Test
- Which metal is liquid at room temperature? (Answer: Mercury.)
- What happens when zinc is added to copper sulphate solution? (Answer: Zn displaces Cu. Blue colour fades. Reddish-brown Cu deposited. Zn + CuSO₄ → ZnSO₄ + Cu.)
- Why is aluminium used for aircraft bodies despite being reactive? (Answer: Al forms a protective oxide layer (Al₂O₃) that prevents further corrosion. It's also very LIGHT.)
- Name an alloy of copper and zinc. (Answer: Brass.)
- What two conditions are needed for rusting? (Answer: Water (moisture) AND oxygen.)
