L2 - Bond Energy and Reactions

In Thermochemistry I,  you learned how potential energy diagrams can be used to communicate enthalpy changes. It is common knowledge that you have to provide a spark, a flame, or energy in another form to get most fuels to combust.

In the previous lesson, you observed that some of the fuels being tested in the spirit lighters were much easier to ignite than others. Using potential energy diagrams, how can you demonstrate the energy necessary to initiate a combustion and the difference in the magnitude of energy required for some fuels?

In this lesson you will investigate how energy is involved in initiating chemical change. In order to better evaluate biodiesel as a fuel, it is necessary to understand the factors that affect how easily some fuels ignite. Your investigation in this lesson may also provide insight into the scientific reasoning behind the suggested practice of storing fuels in a cool, dark place.

Consider the following question as you complete this lesson:

• Why is energy needed to start an exothermic reaction?