Measuring enthalpy changes

• A 1K rise in temp is the same as a 1 degree celsius rise in temp
• Specific heat capacity c is the energy required to raise the temp of 1g of a substance by 1K
• Good conductors have small values of c whilst insulators have high values
• Heat energy is given by symbol q
• $q =$$mc∆T$
• Data book values are obtained using much more sophisticated apparatus than a spirit burner and a beaker of water. Much less heat was transferred to the water in the experiment than expected
• Reasons for less heat transfer / lower experimental value than data book value in spirit burner experiment:

  • Heat loss to the surroundings other than water
  • Incomplete combustion of methanol - CO instead of CO2 this would be seen as black layer of soot on beaker
  • evaporation of methanol from the wick - burner must be weighed ASAP after extinguishing the flame
  • Non-standard conditions - conditions for the experiment unlikely to be exactly standard
• The use of draught screens and an input of oxygen gas could minimise errors from heat loss and incomplete combustion