Chemical Changes

• What is Oxidation?

  Substance gains oxygen
• What is reduction?

  Substance loses oxygen
• When reacted with water :

  What do Group 1 metals make ?

  Metal hydroxide + Hydrogen
• What elements have no reaction with water?

  Magnesium , Zinc , Iron & Copper
• What do you have to react the Group 1 elements that do not react with water with instead?

  Dilute acid
• O xidation

  I s

  L ost

  R eduction

  I s

  G ained
• How do you extract Unreactive metals?

  Found in earths surface
• How can metals which are less reactive than Carbon be extracted ?

  By reduction of Carbon
• Acid + metal ---> Salt + Hydrogen
• Are acids H+ or OH- ?

  H+
• What is neutralisation?

  Acids being neutralised by alkali and bases .
• Acid + Metal oxide ---> Salt + Water
• Acid + Metal carbonate ---> Salt + Water + CO2
• How are soluable salts made?

  Made from acids by reacting them with solid insoluable substances
• OH- in terms of pH scale :

  Alkaline
• H+ in terms of pH scale :

  Acid
• What are Titrations used for ?

  Used to measure volumes of acid & alkali solutions that react with eachother
• What is a strong acid in terms of Ionisation?

  Completely Ionised
• Examples of Strong Acids :

  • Hydrochloric
  • Nitric
  • Sulfuric
• What is a weak acid in terms of Ionisation?

  Partially ionised
• Examples of Weak Acids :

  • Ethanoic
  • Citric
• The stronger acid , the lower the pH .
• As pH scale decreases by 1 unit, Conc of H+ ions increases by 10x
• What is Electrolysis?

  Use of electronic current to break down compounds containing ions into consistuent elements
• What is the Electrolyte?

  Substance used to break down, able to conduct electricity
• + Ions move to cathode
• -- ions move to Anode
• Why is Electrolysis expensive?

  • Melting compounds requires a lot of energy
  • Lots of energy required to produce electrical current
• Metal produced at Cathode
• Non-metals produced at Anode
• Electrolysis in Aqueous solutions :

  + electrode = Hydrogen produced if more reactive than hydrogen

  -- electrode = oxygen produced unless solution contains halide ions
• Why at - electron is oxygen produced unless solution contains halide ions?

  H2O molecules break down producing H ions and hydroxide ions are discharged.
• What does Cryolite do?

  Lowers melting point