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Unit 1•Lesson 1 3 min read

What is Energy? Forms of Energy

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Learning Objectives

Define energy as the capacity to do work.
Identify and provide examples of the major forms of energy: chemical, thermal, radiant, mechanical, electrical, and nuclear.
Understand that energy can be classified as either potential (stored) or kinetic (motion).

The Universe's Power Source

What makes a car move, a light bulb shine, or a person run? The answer to all of these is energy. In science, energy is defined as the capacity to do work or cause a change. Work, in the physics sense, means applying a force to an object to move it over a distance. Energy is what makes everything happen.

All forms of energy can be broadly categorized into two main types: potential energy and kinetic energy.

Potential Energy (PE): This is stored energy. It's the energy an object has due to its position or its chemical composition. A stretched rubber band has potential energy.
Kinetic Energy (KE): This is the energy of motion. Anything that is moving has kinetic energy. A rolling bowling ball has kinetic energy.

Let's explore the different forms energy can take.

Forms of Energy

1.Mechanical Energy: This is the energy associated with the motion and position of an object. It is the sum of an object's kinetic and potential energy. A flying bird has mechanical energy (kinetic from its flight, potential from its height).
2.Thermal Energy (Heat): This is the total energy of the moving particles (atoms and molecules) within a substance. The faster the particles move, the more thermal energy the substance has, and the hotter it feels. A cup of hot chocolate has more thermal energy than a cup of cold water.
3.Chemical Energy: This is a form of potential energy stored in the bonds of chemical compounds. When these bonds are broken during a chemical reaction, the stored energy is released. Food, batteries, and fuels like wood and gasoline are all examples of stored chemical energy.
4.Electrical Energy: This is the energy of moving electrons, which are tiny charged particles. We harness this flow of electrons as electricity to power our homes and devices. Lightning is a powerful natural example of electrical energy.
5.Radiant Energy (or Electromagnetic Energy): This is energy that travels in waves through space. The most familiar form is visible light. Other forms include microwaves, radio waves, X-rays, and infrared radiation (which we feel as heat from the sun or a fire).
6.Nuclear Energy: This is a form of potential energy stored in the nucleus (the core) of an atom. This energy can be released when nuclei are split apart (fission) or joined together (fusion). Nuclear power plants use fission to generate electricity, while the sun is powered by fusion.

Key Terms

**Energy
The capacity to do work or to cause change. The SI unit is the Joule (J).~|~Potential Energy: Stored energy based on an object's position or state.~|~Kinetic Energy: The energy of motion.~|~Mechanical Energy: The sum of potential and kinetic energy in an object used to do work.~|~Thermal Energy: The total kinetic energy of the particles in a substance, often called heat.~|~Chemical Energy: Potential energy stored in the bonds of chemical compounds.~|~Radiant Energy: Energy that travels in electromagnetic waves, such as light.~|~Nuclear Energy: Energy stored in the nucleus of an atom.

Check Your Understanding

1

A battery contains what primary form of energy?

2

The sun warms the Earth primarily through which form of energy?

3

Is a moving train an example of potential energy or kinetic energy?

Next
The Law of Conservation of Energy