Chemical changes

• Reactivity series


  A list of elements ordered by their reactivity
• How to place metals in order of reactivity

  Add the metals to water or acid and see which ones react the most (by how much fizzing there is)
• Reduction


  A reaction where oxygen is removed from a compound
• Why zinc can be extracted from zinc oxide with carbon but magnesium cannot be extracted from magnesium oxide with carbon

  Magnesium is more reactive than carbon, Zinc is less reactive than carbon, Carbon can therefore remove oxygen from zinc oxide but not magnesium oxide
• Ore


  A material containing enough metal in it for it to be economically worthwhile to extract the metal
• General equation for metal + water

  Acid + water -> metal hydroxide + hydrogen
• General equation for metal + oxygen

  Metal + oxygen -> metal oxide
• Displacement reaction


  A reaction in which a more reactive element takes the place of a less reactive element in one of its compounds or in solution
• Carbon is included on the reactivity series because metals below carbon can be extracted by carbon reduction; above carbon by electrolysis
• Hydrogen is included on the reactivity series because metals below hydrogen do not react with acid
• Oxidation


  The loss of electrons
• Reduction


  The gain of electrons
• Steps to write an ionic equation

  Write down the balanced symbol equation 2. Split all ionic compounds into ions. 3. Remove any specator ions
• How to write a half equation

  Write equations for the two metals involved in the ionic equation showing where electrons have been lost or gained
• Al³⁺ + Fe → Fe³⁺ + Al

  Aluminium has been reduced and iron has been oxidised
• Half equations for Al³⁺ + Fe → Fe³⁺ + Al

  Al³⁺ + 3e⁻ → Al, Fe → Fe³⁺ + 3e-
• Balancing ionic equation: Al + Ca²⁺ → Al³⁺ + Ca

  2Al + 3Ca²⁺ →2Al³⁺ + 3Ca
• Mg²⁺ + 2Na → 2Na⁺ + Mg

  Na has been oxidised, Mg²⁺ has been reduced
• 2Al + 3Ca²⁺ → 2Al³⁺ + 3Ca

  Al has been oxidised, Ca²⁺ has been reduced
• Half equations for 2Al + 3Ca²⁺ → 2Al³⁺ + 3Ca


  3Ca2+ + 6e- → 3Ca and 2Al → 2Al3+ + 6e-
• K + Na⁺ → K⁺ + Na

  K has been oxidized, Na⁺ has been reduced
• Half equations for K + Na⁺ → K⁺ + Na

  Na+ + e- → Na and K → K+ + e-
• General equation for metals + acid

  Metal + acid -> a metal salt + water
• General equation for metal oxides + acid


  Metal oxide + acid -> a metal salt + water
• General equation for metal hydroxide + acid

  Metal hydroxide + acid -> a metal salt + water
• General equation for metal carbonate + acid

  Metal carbonate + acid -> a metal salt + water + carbon dioxide
• How to name metal salts

  1st part of the salt from the metal; 2nd part of the name comes from the acid: hydrochloric = chloride; sulphuric = sulphate; nitric = nitrate
• How to extract a metal salt from solution

  The solution is heated gently until crystallisation point and then allowed to evaporate at room temperature
• Redox reaction


  A reaction where the metal atoms lose electrons (oxidised) to become positive ions and non-metal atoms gain electrons (reduction) to form negative ions
• Charge on transition elements

  Shown by using roman numerals in the name. The roman numeral shows the charge on the metal.e.g Copper(II) sulphate has a charge of +2
• General equation for acid + alkali

  acid + alkali -> a metal salt + water
• Acid (in terms of pH)


  A substance with a pH of less than 7
• Acid (in terms of ions)


  A substance which releases H⁺ ions in solution
• (aq)


  Aqueous: when something is dissolved in water. E.g. NaCl(aq) is salt water
• Common acids and their formulae

  • Hydrochloric acid, HCl(aq), Sulphuric acid, H₂SO₄(aq), Nitric acid, HNO₃
• Ions formed by common acids in solution

  HCl forms H⁺ and Cl⁻, H₂SO₄ forms 2H⁺ and SO₄²⁻, HNO₃ forms H⁺ and NO₃⁻
• Neutral solution


  A solution with a pH of 7. Water is an example
• How to measure pH


  With an indicator or pH probe
• Base


  A metal oxide, hydroxide or carbonate that will react with an acid. E.g. copper oxide
• Alkali


  A soluble base. E.g. sodium hydroxide