Energy Types and Transformations You Should Know for the GED Science Test

By Murray Shukyn, Achim K. Krull

You will need to have a general understanding of energy types and transformation for the GED Science test. Energy is power that has the capacity to do work or effect change, and it comes in many forms that can be broken down into two main categories:

  • Kinetic: Energy in motion, including the following forms of energy:

    • Electrical: Electrical energy is the flow of electrons, negatively charged particles in atoms.

    • Electromagnetic (radiant): Various forms of light, including the visible light you’re most familiar with, microwaves, and X-rays, are all forms of electromagnetic energy.

    • Motion: Anything in motion carries energy that’s a product of its mass and velocity.

    • Sound: Sound energy causes vibration and is a relatively small source of energy.

    • Thermal: Although you can’t always see heat move, you can feel it flow from an object or cause steam to rise from water.

  • Potential: Energy at rest, stored in an object by virtue of its position, electrical charge, or other factor(s). Potential energy includes the following forms of energy:

    • Chemical: Energy stored in the bonds among atoms in a compound. When bonds are formed or broken through chemical reactions, energy can be released.

    • Gravitational: Energy exerted on objects by the gravitational field surrounding them. If you do a push-up, you experience gravitational energy acting on your body.

    • Nuclear: Energy stored in the nucleus (core) of an atom. When an atom is split (a process referred to as fission) or two atoms combine (fusion), energy is released. Nuclear power plants use fission to produce energy. Fusion is responsible for most of the energy produced by the sun and other stars.

    • Elastic: The energy stored in a stretched rubber band is elastic energy. If you release the rubber band, the energy is converted into mechanical (motion) energy.

According to the law of conservation of energy, the total energy in a system remains constant; in other words, energy can’t be created or destroyed, although it can be converted from one type of energy to another. For example, when you flip a switch to turn on the lights, electrical energy is converted into electromagnetic energy in the form of light and into heat energy. The electrical energy doesn’t just disappear.

You’re probably most familiar with energy that’s used every day for heating, refrigeration, light, or performing mechanical work to operate machines.

  1. A screw becomes warm when unscrewed from a board using an electric screwdriver. Which of the following best describes the type of energy conversion taking place?

    • (A) mechanical to thermal to electrical

    • (B) electrical to mechanical to thermal

    • (C) gravitational to mechanical to thermal

    • (D) chemical to mechanical to thermal

  2. Trees are damaged when struck by lightning, but the lightning is nowhere apparent afterward. Because lightning is a form of energy, what would explain the apparent disappearance of the energy in the lightning?

    • (A) The energy in the lightning disappears.

    • (B) The tree absorbs the lightning and stores the energy for future use.

    • (C) The energy in the lightning is converted to mechanical and thermal energy.

    • (D) Lightning striking the tree creates new energy, which damages the tree.

Now check your answers:

  1. Electrical energy is converted into mechanical energy to turn the screw, which is then converted into thermal energy in the form of heat, so Choice (B) is correct.

  2. Electrical (and light) energy from the lightning is converted into mechanical energy that causes the tree to split and thermal energy in the form of heat, Choice (C). Based on the law of the conservation of energy, you can instantly rule out Choices (A) and (D) because energy can neither be created nor destroyed. Choice (B) would be a good second guess, but it’s wrong because the tree has no means to store the electrical energy in order to release it later.