In this experiment, you will find and compare the heat of combustion of two different fuels: paraffin wax and ethanol. Paraffin is a member of a group of compounds called alkanes that are composed entirely of carbon and hydrogen atoms. Many alkanes, such as gasoline and diesel oil, are important fuels. Ethanol, C2H5OH, is used as a gasoline additive (gasohol) and as a gasoline substitute. In this experiment, you will compare the energy content of paraffin and ethanol by measuring their heats of combustion in kJ/g of fuel.
In order to find the heat of combustion, you will first use the energy from burning ethanol or paraffin to heat a known quantity of water. By monitoring the temperature of the water, you can find the amount of heat transferred to it, using the formula
where q is heat, Cp is the specific heat capacity of water, m is the mass of water, and Δt is the change in temperature of the water. Finally, the amount of fuel burned will be taken into account by calculating the heat per gram of fuel consumed in the combustion.
In this experiment, you will
Compare the heat of combustion for paraffin wax and ethanol.
Calculate the heat of combustion and percent efficiency for both fuels.
Sensors and Equipment
This experiment requires each of the following Vernier sensors and equipment (unless otherwise noted):
Step-by-step instructions for computer-based data collection
List of materials and equipment
Note: The experiment preview of the computer edition does not include essential teacher information, safety tips, or sample data. Instructions for Logger Pro and other software (such as LabQuest App or TI handheld software, where available) are on the CD that accompanies the book. We strongly recommend that you purchase the book before performing experiments.