1. Module 1

1.35. Page 4

Module 1: Lesson 7

Module 1—Thinking Energy

Lesson Summary


In Lesson 7 you considered the following questions:

  • What is Hess’ law?
  • How does Hess’ law relate to enthalpies of reaction?

Hess’ law is a thermodynamic principle that states that the addition of chemical equations yields a net chemical equation with an enthalpy change equal to the sum of the enthalpy changes of the steps. Hess’ law can be used to determine the enthalpy change for reactions that are not able to be investigated experimentally. You evaluated the process used to investigate chemical reactions as multistep processes, and you completed a laboratory exercise to test a hypothesis made using Hess’ law.