Energetics

• Label this energy profile diagram

  A - energy

  B - progress of reaction

  C - reactants

  D - products

  E- activation energy

  F - negative energy change

  
• Label this energy profile

  A - energy

  B - progress of reaction

  C - reactants

  D - products

  E - activation energy

  F - positive energy change

  
• What type of reaction is this energy profile diagram showing

  Endothermic

  
• What type of reaction is this energy profile diagram showing

  Exothermic

  
• what is another way of writing energy change

  (delta)H
• describe and explain why a reaction is exothermic in terms of bonds

  In an exothermic reaction, less energy is taken in to break bonds and more energy is released when new bonds are made
• describe and explain why a reaction is endothermic in terms of bonds

  In an endothermic reaction, more energy is taken in to break bonds and less energy is released when new bonds are made
• If the energy change in a reaction is positive what type of reaction is it

  endothermic
• If the energy change in a reaction is negative what type of reaction is it

  exothermic
• what is an exothermic reaction

  when energy is released into the surroundings
• what is an endothermic reaction

  when energy is taken in from the surroundings
• what is the calculation for energy change

  (delta) H = (sigma)bonds broken - (sigma) bonds made
• what are 3 examples of everyday uses of endothermic reactions

  • ice melting into water
  • evaporation of water
  • baking bread
• what are 3 examples of everyday uses of exothermic reactions

  • combustion (burning)
  • hand warmers
  • burning a candle
• Label the experiment to show how energy transfer can be measured 


  A = insulated cup

  B = lid with a hole

  C = thermometer

  D = dilute hydrochloric acid

  E = magnesium powder

  
• how to calculate energy transfered and energy per gram

  1 energy transfered = mass of H2O * 4.2 * temperature change

  2 energy per gram = energy transfered / mass of the fuel used
• what are the 2 energetics

  endothermic and exothermic
• Describe the experiment to see if a reaction is endothermic or exothermic (to do with temperature)


  1 add hydrochloric acid to an insulated cup with a hole in its lid (for a thermometre) and record the start temperature

  2 add the other reactant and record the final temperature when the reaction has visibly stopped

  3 calculate the temperature difference by subtracting the start temperature from the final temperature
• what is bond energy 


  the amount of energy that must be transferred to break a mole of a particular covalent bond