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Key Idea: Uncontrolled systems always evolve toward more stable states--that is, toward more uniform energy distribution.

Students should know that:

  1. Unless prevented from doing so, energy will become uniformly distributed among the atoms/molecules within a system or between the system and the surrounding environment.
  2. When energy becomes uniformly distributed, the amount of energy present has not changed but the energy becomes less useful and less concentrated.
  3. After a given amount of energy had become uniformly distributed, it takes additional energy to concentrate the diffuse energy and make it useful again.
  4. Thermal energy in the surrounding environment is sometimes considered a less useful type of energy.



  1. Items do not ask students to perform any calculations. For example, students are not asked to use equations like KE = 1/2mv2 or PE = mgh.
  2. Items do not assess students’ understanding of entropy or the relationship between energy and entropy.

No misconceptions are associated with this idea in the selected project.

No NGSS statements are associated with this idea in the selected project.