Investigating the Energy Content of Fuels

Introduction

Hydrocarbons are compounds containing only hydrogen and carbon atoms. Many common fuels such as gasoline, diesel fuel, heating oil, aviation fuel, and natural gas are essentially mixtures of hydrocarbons. Paraffin wax, used to make many candles, is a mixture of hydrocarbons with the representative formula C₂₅H₅₂.

Ethanol, a substituted hydrocarbon with the formula CH₃CH₂OH, is used as a gasoline additive (gasohol) and as a gasoline substitute. Ethanol is an alcohol—a hydrocarbon derivative in which one or more hydrogen atoms has been replaced by a hydroxyl group (–OH). 1-propanol (CH₃CH₂CH₂OH), 2-propanol (CH₃CH(OH)CH₃), and 1-butanol (CH₃CH₂ CH₂CH₂OH) are other common alcohols.

Objectives

In the Preliminary Activity, you will determine the heat of combustion of paraffin wax (in kJ/g). You will first use the energy from burning paraffin wax to heat a known quantity of water. By monitoring the temperature of the water, you can find the amount of heat transferred to it (in kJ), using the formula

where q is heat, C_p 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 paraffin wax consumed in the combustion.

After completing the Preliminary Activity, you will first use reference sources to find out more about calorimetry and fuels before you choose and investigate a researchable question.