Final answer:
The best synonym for 'harness' in the context of energy is 'Use,' which refers to controlling and making use of energy to perform work or generate power, through processes that often involve energy conversion and transfer.
Step-by-step explanation:
The best synonym for the word harness in the context of energy changes is Use. This word accurately describes the action of controlling and making use of energy resources to perform work or generate power. Humans have been able to harness energy changes, allowing for the development of technology, advancements in industry, and overall improvements in the quality of life.
Harnessing energy often involves converting one form of energy into another more useful form, such as turning kinetic energy from wind into electrical energy with wind turbines. However, it's important to note that while energy conversion and efficient transfer of energy are key to harnessing energy, most processes eventually lead to waste heat, which is less useful for doing work, as per the principles of thermodynamics.