chemistry chemical reactions

• Thermal decomposition reaction


  A reaction where heat is used to break down a compound
• Products of thermal decomposition of a metal carbonate

  • Metal oxide
  • Carbon dioxide
• Testing for carbon dioxide

  Turn limewater cloudy
• Oxidation


  A reaction involving a substance gaining oxygen
• Oxidation of magnesium


  Magnesium (s) + oxygen (g) → magnesium oxide (s)
• Metal displacement reaction


  A more reactive metal will take the place of a less reactive metal in a compound
• How to tell if a metal is more reactive than another

  It is higher in the reactivity series
• Exothermic reaction


  Energy is transferred to the surroundings, they become hotter
• Endothermic reaction


  Energy is taken in from the surroundings, the surroundings become colder
• Bond breaking needs energy
• Bond making releases energy
• Properties of acids


  • Soluble in water
  • Release hydrogen ions [H+] when dissolved
  • React with metals to produce a salt and hydrogen
  • React with alkalis to produce a salt solution and water
• Common lab acids


  • Hydrochloric acid
  • Nitric acid
  • Sulfuric acid
• Properties of alkalis


  • Soluble in water
  • React with acids to produce a salt solution and water
  • Contain hydroxide ions (OH-)
• Common lab alkalis


  • Sodium hydroxide
  • Potassium hydroxide
  • Ammonia
• Indicator


  A chemical that changes colour when added to acids and alkalis
• Indicators


  • Litmus paper
  • Litmus solution
  • Universal indicator paper
  • Universal indicator solution
• Blue litmus paper turns red in acid
• Red litmus paper turns blue in alkali
• pH scale


  Shows how acidic or alkaline something is
• pH for neutral substances is 7
• pH range for acids is 1-6
• pH range for alkalis is 8-14
• Substance with pH 2


  More acidic than substance with pH 5
• Substance with pH 13

  More alkaline than substance with pH 8
• Universal indicator colour scale shows pH
• pH probe


  A devise to measure pH digitally
• pH probe


  • It has a higher resolution and is more precise
• Neutralisation


  A reaction where an acid and alkali are reacted together
• Product of acid-alkali reaction


  Salt and water
• Types of salts


  • Chlorides
  • Nitrates
  • Sulfates
• When a metal oxide and acid react, salt and water are formed
• When a metal carbonate and acid react, salt, water and carbon dioxide are formed
• Acid rain formation


  1. Burning fuels produces carbon dioxide and/or sulfur dioxide and/or nitrous oxides

  2. These dissolve in rain clouds
• Human actions that produce greenhouse gases

  • Burning fossil fuels in cars and power stations
  • Burning coal that contains sulfur impurities
  • High temperatures in car engines cause nitrogen and oxygen in the air to react
• Thermal decomposition


  A reaction where heat is used to break down a compound
• Products of thermal decomposition of a metal carbonate

  Metal oxide and carbon dioxide
• Testing for carbon dioxide

  Turns limewater cloudy
• Oxidation


  A reaction involving a substance gaining oxygen
• Oxidation of magnesium


  Magnesium (s) + oxygen (g) → magnesium oxide (s)