chemical changes and energy changes

• Reduction

  The loss of oxygen
• Oxidisation


  The gain of oxygen
• Oxidisation and reduction always occur together
• Reactivity series

  Order of metals reactivity in terms of reaction with water and acid
• most reactive metals

  Lithium, Sodium, potassium
• Least reactive metals

  Copper, gold
• Mid reactive metals

  Calcium, magnesium, zinc and ion
• In a displacement reaction a more reactive metal will displace a less reactive metal
• magnesium is more reactive than copper, so magnesium will displace copper from a solution of copper sulfate
• Method of extraction depends on how reactive a metal is
• Oxidisation is the loss of electrons
• Reduction is the gain of electrons
• Indicators


  dyes that change colour depending on the pH of a sultion
• pH of an acid

  0 to 6
• pH of a neutral solution

  7
• pH of an alkaline

  8 to 14
• acids contain hydrogen ions
• Alkalis contain hydroxide ions
• When an acid and alkali react, the H+ and OH- react together to produce water
• Neutralisation

  when and acid is Neutralised by an alkali
• a salt is produced when hydrogen in the acid is replaced by a metal ion
• Soluble salts can be made by reacting acids with insoluble bases (metal oxides, metal hydroxides, metal carbonates)
• Strong acids are completely ionised in water
• Hydrochloride acid is a strong acid
• Ethan ooc acid I’d a weak acid
• The pH of a solution is a measure of the concentration of H+ ions
• Electrolysis


  the use of an electrical current to break down compounds containing ions
• The substance being broken down is called an electrolyte
• Electrodes are usually made out of

  Graphite, as they need to conduct electricity p
• Anode

  Positive electrode that attracts negatively charged ions
• Cathode

  Negative electrode that attracts positively charged ions
• Reduction occurs when positively charged ions gain electrons at the negative electrode
• Oxidisation occurs when th negatively charged ions lose electrons at the positive elctrode
• Reactions that occur at the electrodes can be represented by half equations
• Metals that are more reactive than carbon can be extracted from their ores by electrolysis
• Electrolysis requires a lot of heat and electrical energy, making it an expensive process