Energy comes in many forms such as light, heat, motion, and potential energy. Chemical fuels such as natural gas and gasoline are chemicals that have a lot of potential energy, which is energy that is stored in the bonds of the molecules. Because they have so much energy stored in them, these fuels have the potential to release energy when their bonds are rearranged and made more stable. Such bond rearrangements release energy into the surroundings often causing a temperature increase. By measuring the temperature increase, it is possible to determine how much energy was released and thus how much energy was originally stored in the molecules. In this experiment, you will find and compare the energy released (heat of combustion) for two different fuels: paraffin wax and ethanol. Paraffin is a member of a group of compounds called hydrocarbons that are composed entirely of carbon and hydrogen atoms. Hydrocarbons include natural gas, wax, gasoline, and diesel. Ethanol, C2H5OH, can also be used as a fuel. In this experiment, you will compare the energy content of paraffin and ethanol by measuring their heats of combustion in kJ/g.
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 increase of the water, you can find the amount of heat transferred to it, using the formula q = Cp•m•T where q is heat, Cp is the heat capacity of water, m is the mass of water, and T