Reactions: Chemical energy and types of reaction

• Distinguish between endothermic and an exothermic reaction?


  Exothermic reactions occur when there is more energy in the reactants then is needed to form the products so energy is released to the surrounding. On the other hand, endothermic reactions don't have enough energy to form the products and so has to take in energy from the surroundings.
• Give 2 examples of reactions that are exothermic?


  1. Water and calcium oxide
  2. Combustion
• Give 2 examples of reactions that are endothermic?

  1. Water and ammonia
  2. Sodium carbonate and Ethanoic acid
• Draw and annotate an energy level diagram for an exothermic reaction?


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• Draw and annotate an energy level diagram for an endothermic reaction?

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• What is a catalyst?


  Catalysts are chemicals that speeds up certain reactions. They are not part of the reaction
• What is an enzyme?


  Enzymes are proteins that help speed up metabolism, or the chemical reactions in our bodies.
• Name one industrial process that uses a catalyst?

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• Which catalyst is found in a catalytic convertor in a car?


  Catalytic converters clean up emissions from gasoline and diesel vehicles using metal catalysts which usually contain platinum, palladium and rhodium.
• Define physical change and give an example?

  Physical changes are changes affecting the form of a chemical substance, but not its chemical composition. This means that it can be undone. E.g. Melting an ice cube
• Define chemical change and give an example?

  A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. These cannot be undone. E.g. Frying an egg
• List 4 observations that indicate that a chemical change has taken place?


  • colour change.
  • effervescence.
  • precipitation.
  • temperature change.
• Complete this equation: Metal + acid =?

  When an acid reacts with a metal, the products are a salt and hydrogen.
• Complete this equation: Magnesium + hydrochloric acid = ?


  Magnesium chloride and hydrogen
• Complete this equation: Iron + sulphuric acid = ?


  Iron sulphide and hydrogen
• Complete this equation: Zinc + nitric acid = ?

  Zinc nitride and hydrogen
• What is the general equation for a reaction of an acid and a metal carbonate?


  Metal carbonate + acid = salt, carbon dioxide and water
• Complete this equation: Magnesium carbonate + hydrochloric acid = ?


  Magnesium chloride + carbon dioxide + water
• Complete this equation: Copper carbonate + sulphuric acid = ?


  Copper sulphide + carbon dioxide + water
• What is thermal decomposition?


  Thermal decomposition is a chemical decomposition of a substance caused by heat.
• Write a word equation for the thermal decomposition of calcium carbonate?

  Calcium carbonate -> calcium oxide + carbon dioxide
• How and why does the mass change during the thermal decomposition of calcium carbonate?


  The mass appears to have decreased because one of the products, carbon dioxide, escapes to the air.
• Write a general equation for the reaction of a metal oxide and an acid


  Metal oxide + acid -> salt + water
• Complete this equation: Copper oxide + hydrochloric acid = ?


  Copper chloride + water
• Complete this equation: Zinc oxide + sulphuric acid = ?


  Zinc sulphide + water
• Why is the reaction of a metal oxide and an acid known as a neutralisation reaction?


  When acid and base react with each other, they form salt and water. Water and salt both are neutral which means, that whenever acid and base react together, they are neutralised by each other.
• In an experiment that demonstrates the products of combustion, what happens to the temperature, the limewater and the cobalt chloride paper, and why?


  In the above experiment, the limewater in the boiling tube changes colour indicating carbon dioxide is produced by combustion of the hydrocarbon fuel. If water is produced it will condense in the u tube cooled by the ice water. This results in cobalt chloride paper changing colour from blue to pink.