4 - Chemical Changes

• Oxidation is the loss of electrons

  Reduction is the gain of electrons
• Metal + water -> Metal Hydroxide + hydrogen
• Metal + acid -> salt + hydrogen
• In a displacement reaction, a more reactive metal will displace a less reactive metal from its compound.

  e.g: silver nitrate + copper -> silver + copper nitrate

  • Copper is more reactive than silver so displaces it from its compound
• Acidic solutions contain hydrogen ions (H+)

  Alkaline solutions contain hydroxide ions (OH-)
• Metal Carbonate + acid -> salt + water + carbon dioxide

  e.g:

  sodium carbonate + nitric acid -> sodium nitrate + water + carbon dioxide

  Na₂CO₃ + 2HNO₃ → 2NaNO₃ + H₂O + CO₂
• Metal hydroxide + acid -> salt + water
• Metal oxide + acid -> salt + water
• What is a redox reaction?

  A reaction where one reactant is reduced (gains electrons) and another is oxidised (loses electrons)
• The reactivity of a metal is related to its tendency to form positive ions
• A redox reaction is a reaction where one substance is reduced and another is oxidised
• Acid + alkali -> salt + water
• Strong acids are completely ionised in aqueous solution
• Weak acids are partially ionised I’m aqueous solution
• Concentration of an acid refers to the amount of a substance in a given volume. Strength refers to the H+ ion concentration in aqueous solutions