Class 10 Science Notes — Chapter 3: Metals and Non-metals
Physical and chemical properties, reactivity series, extraction, and corrosion.
Detailed NCERT notes
- Physical properties of metals: lustre, malleable, ductile, sonorous, good conductors of heat and electricity, high melting points (exceptions: Hg is liquid; Na, K are soft; Ga, Cs melt in palm).
- Physical properties of non-metals: dull (except iodine), brittle, non-sonorous, poor conductors (exception: graphite conducts).
- Metals react with oxygen → basic oxides (some amphoteric like Al₂O₃, ZnO which react with both acids and bases).
- Metals react with water: K/Na violently with cold water; Mg with hot water; Al/Zn/Fe with steam. Cu, Ag don't react.
- Reactivity series (decreasing): K, Na, Ca, Mg, Al, (C), Zn, Fe, Pb, (H), Cu, Hg, Ag, Au.
- Displacement rule: a more reactive metal displaces a less reactive one from its salt solution.
- Ionic (electrovalent) bond: formed by transfer of electrons — metal loses, non-metal gains. E.g. NaCl. Properties: high m.p., soluble in water, conduct electricity in molten/solution state.
- Extraction depends on reactivity:
- Highly reactive (K, Na, Ca, Mg, Al): electrolysis of molten chloride/oxide.
- Middle (Zn, Fe, Pb, Cu): roasting (sulphide ore + air) or calcination (carbonate ore + limited air) → oxide, then reduction with carbon.
- Low reactivity (Ag, Au): found free in nature or as sulphide; reduction not needed.
- Refining of metals: electrolytic refining (impure anode, pure cathode, salt solution as electrolyte).
- Corrosion of metals: iron rusts (Fe₂O₃·xH₂O), silver tarnishes (Ag₂S), copper turns green (basic carbonate).
- Prevention: painting, oiling, greasing, galvanisation (zinc coating), electroplating, alloying.
- Alloys: solid solutions of metals; better properties. Steel (Fe + C), Stainless steel (Fe + Cr + Ni), Brass (Cu + Zn), Bronze (Cu + Sn), Solder (Pb + Sn), Amalgam (Hg + metal).
Formulas & key results
- Reactivity series: K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Ag > Au
- Roasting (sulphide + O₂) → oxide; Calcination (carbonate + Δ) → oxide
- Reduction: MO + C → M + CO
Mind map
- Properties → reactivity → ionic bond → extraction → corrosion → alloys
Tricks & shortcuts
- Higher in reactivity series → more vigorous with water and stronger displacement.
- Roasting = sulphide, Calcination = carbonate.
Common mistakes to avoid
- Confusing roasting and calcination.
- Assuming all metals react with water.
Competency-based questions & answers
- Q. Why is sodium stored in kerosene?A. Sodium is highly reactive; reacts vigorously with air/moisture forming NaOH + H₂ (can ignite). Kerosene prevents contact.
- Q. Why is aluminium used to make cooking utensils despite being reactive?A. It forms a thin, dense, protective layer of Al₂O₃ on its surface which prevents further reaction.
- Q. Explain galvanisation.A. Coating iron with a thin layer of zinc; zinc is more reactive, so it corrodes preferentially (sacrificial protection).