MHS Chemistry
Heat Of Combustion


Fuels are chemical compounds that release useful heat on demand.  Some release heat slowly, like iron (in mitten warmers) or coal.  Others release heat very quickly, like gasoline.  In this experiment, we will determine the amount of energy that a given mass of fuel (candle wax) releases.  To do this, we will measure the amount of energy that a known mass of water absorbs.  Groups will develop and carry out their own procedures.  Heat of combustion is measured with units of energy per mass, in"J/g" of the fuel.

Notes & Hints

  1. Decide what information you will need to record. Prepare a procedure and blank data table in your notebook. You may not work at the lab bench until I have signed your procedure and data table.
  2. You should perform at least three trials.
  3. Hint #1:  What is the formula for calculating heat?
  4. Hint #2:  How do you go about measuring heat?  Refer to previous labs and your text for specifics.
  5. Hint #3:  Decide if it is better to heat the water for a specific amount of time, or a specific temperature change.
  6. Record all data properly and carefully, and show all calculations clearly.  Don't forget to label them AND describe them.


  1. Is the heat absorbed by the water really the same as the heat given off by the fuel?  Is it reasonable to assume this? Explain your reasoning.
  2. Is q(water) positive or negative?
  3. Is q(fuel) positive or negative?
  4. Is Dm(candle) positive or negative?
  5. Is Dm(fuel used) positive or negative?

Write Up

This lab should include a title section, purpose, procedure, data, calculations & results, and answers for the questions in the analysis section. Don't forget: show the calculations for the first trial but show the final results for all trials. Include an average result.

[Heat of Combustion score sheet][Heat and Energy notes][MHS Chem page]