Key Idea: The total change of energy in any system is always equal to the total energy transferred into or out of the system.
Students should know that:
- Even though the forms of energy present within a system may change, the total amount of energy in the system remains the same unless energy is added to or released from the system.
- If the total amount of energy in a system decreases or increases, an equal amount of energy must have gone to or come from somewhere outside the system.
- If no energy enters or leaves a system, a decrease of one form of energy by a certain amount within the system must be balanced by an increase of another form of energy by that same amount within the system (or a net increase of multiple forms of energy by that same amount). Similarly, an increase of one form of energy by a certain amount within a system must be balanced by a decrease of another form of energy by that same amount within the system (or a net decrease of multiple forms of energy by that same amount).
- Energy can neither be created nor destroyed but it can be transferred and/or transformed within and between systems.
- If energy is transferred to or from a very large system (or a very complex system), increases or decreases of energy may be difficult to detect and, therefore, it may appear that energy was not conserved.
Boundaries:
- Assessment items avoid using the phrase “energy conservation” or “conservation of energy” because students often associate these terms with efforts to conserve energy resources.
- Assessment items do not ask students to make calculations about the amount of energy in a system or about changes in energy. Students are not expected to know about energy-mass conversions such as nuclear reactions or other subatomic interactions.
Item ID Number |
Knowledge Being Assessed | Grades 6–8 |
Grades 9–12 |
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No misconceptions are associated with this idea in the selected project.
No NGSS statements are associated with this idea in the selected project.