A fire in a fireplace on a cold winter night is welcome and comforting. The organic compounds that make up wood react with oxygen at an elevated temperature to produce carbon dioxide, water vapor, and large amounts of heat. Combustion is an example of an exothermic chemical reaction, meaning that heat is released in the course of the reaction. When you sit in front of this fire, the heat energy flows from the fire to you. In this chapter, you will learn about heat flow and how some chemical reactions naturally release energy while some other reactions absorb energy. You will learn how to show heat changes in chemical equations and perform calculations in order to determine the heat being absorbed or released in all sorts of chemical reactions, changes of state, and other physical processes.
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