Light - Light is a product of energy that is visible to the human eye. Applied Concept: The most common source of light is thermal energy. Light sources include the sun, incandescent bulbs, and flame.
Potential energy - Potential energy (PE) is energy stored in a physical system; this energy can be released or converted into other forms of energy. Forms of potential energy include elastic, electrical, thermal, gravitational, and chemical.
Entropy - Entropy is the tendency to evolve to a state of uniformity. Entropy is loosely referred to a breakdown of a system. Applied Concept: Examples of Entropy include–melting ice (change of temperature, until of the water equals the temperature of the room); shuffling a new card deck (change of organization, until the cards are randomly distributed); spraying air freshener (change of concentration, until the entire room smells the same).
Friction - Friction is the force that resists motion when one object is rubbed against another. Friction always opposes movement. Applied Concept: If you were to hit a hockey puck across ice it would travel further than hitting a hockey puck across asphalt, due to ice having much less friction than asphalt.