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What is energy?  

Energy is the ability to do work

Scientists define energy as the ability to do work. Modern civilization is possible because people have learned how to change energy from one form to another and then use it to do work. People use energy for a variety of things, such as to walk and bicycle, to move cars along roads and boats through water, to cook food on stoves, to make ice in freezers, to light our homes and offices, to manufacture products, and to send astronauts into space.

There are many forms of energy:

  • Heat
  • Light
  • Motion
  • Electrical
  • Chemical
  • Gravitational

These forms of energy can be grouped into two general types of energy for doing work:

  • Potential, or stored, energy
  • Kinetic, or working, energy

Energy can be converted from one form to another. For example, the food you eat contains chemical energy, and your body stores this energy until you use it as kinetic energy during work or play. The stored chemical energy in coal or natural gas and the kinetic energy of water flowing in rivers can be converted to electrical energy, which can be converted to light and heat.

Energy sources are renewable or nonrenewable

There are many different sources of energy, but they can all be divided into two categories:

Renewable and nonrenewable energy sources can be used as primary energy sources to produce useful energy such as heat, or they can be used to produce secondary energy sources such as electricity and hydrogen.

Last updated: August 16, 2023