Energy is an integral component of chemical reactions. Some reactions require an input of energy, whereas others release energy as they proceed. When we burn propane, we are oxidizing small hydrocarbons by reacting them with oxygen. This reaction produces heat, which can be used to heat a barbeque for cooking or fill a balloon with hot air so it can soar over the countryside. In this chapter, we will focus primarily on the transfer of heat and energetic changes that occur during chemical reactions.
Adrian Pingstone. commons.wikimedia.org/wiki/File:Flame.inflates.balloon.bath.arp.jpg. Public Domain.