How do you measure the enthalpy change of combustion of methane using a saucepan?

Answer 1

Enthalpy change of Methane.

• In this case your saucepan is the calorimeter, although i would use a metal that conducts better e.g. a copper cup
  
• measure the mass of the saucepan.
• Measure the mas of saucepan + the amount of water your using (this could be anything)
• Minus this number from the original mass of the calorimeter to give the total mass of the water.

• record the starting temperature of the water and decide when to stop the combustion (e.g. after a 10 degree rise 20, 30 ,40 etc.-normally this is done in kelvin by adding 273 to Celsius
  
• Measure the mass of the fuel your going to burn beforehand often youll need some sort of burner to do this.

• Light your fuel (methane) and put the saucepan over it (this will turn the pan black) make sure the flame has as little movement as possible - keep the pan directly over the heat.
• After the water has risen the set amount stop.
  
• Measure the mass of the methane left.(mass of fuel and burner before - mass of fuel and burner after)

• Using the formula energy transferred =cm deltaT where c is the heat capacity of water 4.18Jg-1K-1 m is the mass of water in grams and deltaT is the change in temperature, this will be the same in Kelvin and Celsius
• Calculate the energy transferred (deltaHc)

Extension

• The energy transferred above is for the mass of fuel burned we want the energy transferred for 1 mole of methane. (energy released per mole)
  

• Work out how many moles of methane you used. number of moles =mass in grams / the molar mass. (formula for methane is CH4 therefor molar mass= 12+(4*1)

• Now you need the energy released per mole of methane ( how many times does the number moles calculated divide into 1 molar of methane.
  

• For this you do (1/number of moles *the energy transferred) all divided by 1000 to give the energy per mole in kilo joules

NOTE: this answer will vary extremely from the true value of enthalpy levels of methane (840.4 KJ-1) as the true value is calculated using standard conditions: a specified temperature , standard atmospheric pressure and standard concentration of fuel.

NOTE: this experiment is just an extreme estimate of the true value as heat is not constantly distributed to the water energy is lost to the air and saucepan etc.