A fast, one-glance recap of Class 10 Science Chapter 3 (Metals and Non-metals) — for the full worked explanations, see the Solutions.
Revision Notes: Metals and Non-metals
- Physical properties of metals: lustrous, malleable (can be beaten into sheets), ductile (can be drawn into wires), sonorous, good conductors of heat and electricity, generally solid at room temperature (mercury is a liquid exception)
- Physical properties of non-metals: generally dull (except iodine), brittle, poor conductors (except graphite), can be solid, liquid (bromine) or gas at room temperature
- Metal + Oxygen → Metal oxide (basic in nature) — e.g. 2Mg + O2 → 2MgO
- Amphoteric oxides: react with both acids and bases — e.g. Al2O3, ZnO
- Non-metal + Oxygen → Non-metallic oxide (acidic or neutral) — e.g. S + O2 → SO2 (turns moist blue litmus red)
- Metal + Water → Metal oxide/hydroxide + Hydrogen (reactivity dependent: K and Na react violently with cold water; Ca, Mg react with water more mildly; Al, Fe, Zn react only with steam; Pb, Cu, Ag, Au do not react with water at all)
- Metal + Dilute acid → Salt + Hydrogen (only metals above hydrogen in the reactivity series; test: burning splinter gives a pop sound)
- Reactivity series (high to low): K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Ag > Au
- Displacement reaction: a more reactive metal displaces a less reactive metal from its salt solution — e.g. Fe + CuSO4 → FeSO4 + Cu
- Ionic (electrovalent) compounds: formed by transfer of electrons between a metal and a non-metal; generally have high melting/boiling points, are soluble in water, insoluble in solvents like kerosene/petrol, and conduct electricity only when molten or in solution (not as solids)
- Occurrence of metals: highly reactive metals (K, Na, Ca, Mg, Al) occur as oxides/carbonates/chlorides/sulphates; moderately reactive metals (Zn, Fe, Pb, Cu) occur mainly as sulphides/carbonates; least reactive metals (Au, Ag, Pt) occur as free elements
- Extraction steps: (1) Enrichment/concentration of ore (e.g. froth flotation for sulphide ores) → (2) Conversion to oxide (calcination for carbonate ores, roasting for sulphide ores) → (3) Reduction of oxide to metal (using carbon, or by electrolysis for very reactive metals, or using a more reactive metal like aluminium in the thermit reaction) → (4) Refining (commonly electrolytic refining) to obtain the pure metal
- Thermit reaction: Fe2O3 + 2Al → 2Fe + Al2O3 + heat — used to weld railway tracks/cracked machine parts
- Electrolytic refining: impure metal = anode, pure metal strip = cathode, salt solution of the same metal = electrolyte; pure metal deposits at the cathode, impurities settle as anode mud
- Corrosion: gradual destruction of metals by reaction with substances in their environment (e.g. iron → rusting, copper → green tarnish, silver → black tarnish)
- Preventing corrosion: painting, oiling/greasing, galvanising (zinc coating), alloying, electroplating
- Alloys: homogeneous mixtures of two or more metals (or a metal and a non-metal) that improve on the properties of the pure metal — e.g. stainless steel (Fe + Cr + Ni, rust-resistant), brass (Cu + Zn), bronze (Cu + Sn), solder (Pb + Sn, low melting point)
- Aqua regia: freshly prepared 3:1 mixture of concentrated HCl and concentrated HNO3; can dissolve gold and platinum, which do not react with either acid alone
See also: Extra Questions (HOTS) | Class 10 Science Formulas Handbook
