calorimetry

• How can a simple calorimeter be made?

   from a polystyrene drinking cup, a vacuum flask or metal can

  ( need a plastic lid and thermometer)
• What is specific heat capacity?

  • The energy needed to increase the temperature of 1 g of a substance by 1 oC is called the specific heat capacity (c ) of the liquid
  • The specific heat capacity of water is 4.18 J g-1 K-1
• How can the energy transferred as heat be calculated?

  q=mc^T
• What does the q in q=mc^T represent, what are the units?

  the heat transferred

  J
• What does the m in q=mc^T stand for, what are the units?

  the mass of water (usually)

  g
• What does the c in q=mc^T stand for, what are the units?

  the specific heat capacity

  J g-1 oC -1
• What does ^T in q=mc^T stand for, what are the units?

  the temperature change

  oC
• What are the advantages of using a bomb calorimeter?

  minimises heat loss

  pure oxygen used, thus ensures complete combustion
• Why might experimental methods for enthalpy determination not be accurate?


  heat is lost to the surroundings

  not in standard conditions

  reaction may not go to completion
• What is calorimetry?

  an experimental method for finding enthalpy change, which works by measuring temperature change over time

  when recorded and plotted on a graph, data can be extrapolated to the exact point at which the reaction starts, giving a more accurate value for the change in temperature
• What is specific heat capacity?

  the energy required to raise 1g of substance by 1K without a change of state
• how can enthalpy change per mole be calculated?


  ^H= q / n
• sources of error in calorimetry?

  heat loss can occur due to conduction or convection - heat lost to surroundings can be reduced by putting a lid on the calorimeter and insulating the outsides of the calorimeter, using an insulator like polystyrene