Forms of Energy

  • Energy is found in different forms, but all energy falls into the following two categories – potential energy and kinetic energy.
  • Potential energy is stored energy, or the energy of position. It consists of the following forms:
    • Chemical energy is energy stored in the bonds between atoms in molecules.
      • Examples include energy stored in petroleum, natural gas, propane, coal, and biomass.
      • When a chemical reaction takes place, the bonds of atoms are rearranged by being broken or by forming new bonds.
        • Exothermic chemical reactions break their bonding to release thermal energy.
          • Example: gasoline releases energy by burning in a vehicle engine.
        • Endothermic chemical reactions cause molecules to bond. This reaction absorbs thermal energy.
          • Example: photosynthesis absorbs light energy to produce glucose (sugar) and oxygen.
    • Nuclear energy is the stored energy of the nucleus, or center, of an atom.
      • Nuclear fission occurs when the nuclei of atoms are split apart.
        • In nuclear power plants, the nuclei of uranium or plutonium atoms are broken apart to release huge quantities of energy. Plutonium is created in this process by a nuclear change from specific isotopes of uranium.
      • Nuclear fusion occurs when the nuclei of atoms combine to release large amounts of energy in the form of heat and electromagnetic radiation and form a different element. In the sun, hydrogen atoms combine to form helium. Other elements can be formed in other types of stars. This is how different elements were created in the universe.
Examples include a coiled spring, a stretched rubber band, and a compressed gas or liquid. As these bonds are stretched, they absorb energy; as they are let go, the energy is released.
      • Elastic energy, or stored mechanical energy, is energy stored in objects because of a force being applied.
      • Gravitational energy is stored energy associated with gravity because of position or place.
        • Examples include a roller coaster poised at the top of a steep hill, and water in a reservoir behind a dam.
Example of Radiant Energy: You can cook food using radiant energy and even warm your hands by a campfire without sticking your hands into the fire. Other examples of radiant energy include visible light waves such as the light from a light bulb and invisible waves such as solar energy, radio waves, and microwaves.
  • Kinetic energy is the energy of motion. It consists of the following forms:
    • Radiant energy is the energy of electromagnetic radiation traveling in waves.
      • Radiant energy is energy transfer at a distance without direct contact between the energy source and the energy receiver.
      • Electromagnetic waves are produced by the motion of electrically charged particles.
        • These particles travel through empty space as well as through air and other substances.
    • Thermal energy, or heat, is the internal energy in substances caused by atoms and molecules moving and colliding with each other.
      • The flow of thermal energy is called heat transfer.
        • Temperature is a measure of the average heat in a substance.
        • The faster the molecules of matter move, the hotter the substance gets.
        • When something feels hot, it is actually heat transfer to you. When it feels cold, that is heat transfer from you.
      • Heat from the earth (geothermal energy) is an example of thermal energy.
Rainbow Slinky Echo Reverberation: The look of a longitudinal vibration (if it would be visible) may be compared with that of a stadium crowd performing "The Wave." Sound cannot travel through a vacuum because a vacuum has no atoms to transmit the longitudinal vibration. ("The Wave" does not occur in an empty stadium.)
    • Sound energy is the movement of energy in longitudinal waves through a substance (solid, liquid, or gas).
      • Sound is produced when a force causes a substance to vibrate.
        • Examples are voices, music, echoes, and sonic booms.
      • Sound travels in longitudinal vibrations.
    • Motion energy is the movement of substances and objects from one place to another when a force is applied.
      • Examples are hydropower and wind power.
        • Electrical energy is the movement of electrons.
          • Electrons are the negatively-charged particles in atoms.
            • Electricity is the movement of electrons through a wire.

Volts and amperes (amps) are measures of electricity. A volt is the measure of electric pressure that causes electrons to move from one atom to another. It is supplied by a battery or a generator. An amp is the unit used to measure electric current. Current is electricity in motion.

Atomic Structure of Oxygen
The nucleus of an atom consists of protons and neutrons. Electrons orbit around the nucleus. (Nuclei is the plural of nucleus.)
          • Examples of electrical energy include alternating currentAlternating current is when the flow of electricity changes direction back and forth (AC) to supply electricity to households and direct currentDirect current is when electricity flows only one direction. (DC), like using batteries to run an electronic toy or game.
            • Lightning is an example of electrical energy in nature, as is the static that builds up on your body.