In our discussion of electric heaters, you may have noticed that energy was continually “transformed” or “converted” between forms. However, energy was never “produced” or “created”. Energy cannot be created from nothing. This is the Law of Conservation of Energy. Although processes such as fossil fuel combustion are often referred to as energy “production” or “generation”, the combustion process does not actually produce energy. Rather, the difference in potential energy between that in the fossil fuels and oxygen (the reactants) and carbon dioxide and water (the products) is released.

Similarly, in our example, energy is never destroyed; energy does not simply disappear. This is the other half of the Law of Conservation of Energy. Nevertheless, during the many energy transformations required by an electric heater, we often say that energy is “lost”. What does this mean?

Question For Thought

What do you think it means for energy to be “lost”, when energy is being transformed from one form to another?

The answer to this question will be explored in Key Idea 4: Work.