Chapter 4.1: Making Things Happen: Energy

Energy

the ability of matter to move from one place to another or from one state to another.

Work

a broad definition for the energy entering or leaving a system that physically moves an object. It exists when energy is transferred between the surrounding environment and a system.

Heat

the flow of thermal energy between two objects of different temperatures.

Kinetic energy

the energy of an object in motion.

Potential energy

energy that is stored and can be used later.

Elastic energy

energy stored in an object when force is applied, such as when it is stretched or compressed.

Chemical energy

a form of potential energy stored in chemical bonds between atoms.

Nuclear energy

energy stored in the nucleus of an atom.

Electrical potential energy

energy stored in the electrical field between charged particles.

Gravitational potential energy

energy of an object due to its position and height.

Thermal energy

the sum total of the motion, or kinetic energy, of molecules in a system.

Electrical kinetic energy

energy possessed by moving electrical charges, primarily electrons, as they flow through a conductor.

Gravitational kinetic energy

the energy of a moving object as it falls. It is greatest when potential energy is smallest.

Heat or thermal energy

the flow of energy between two objects of different temperatures.

Atomic activity

the faster and more furiously molecules move, the hotter the object feels.

Heat transfer

the process of increasing activity at the atomic level of other materials or objects.

Conduction, convection, and radiation

the three ways heat moves between objects.

Conduction

occurs when a heated material physically touches another material, transferring thermal energy.

Convection

the process of transferring heat through the motion of flowing material, most often a liquid or gas.

Convection cell

the circular motion created when hotter material moves upward and cooler material moves downward.

Radiant heat

heat energy transferred as a wave.

Radiation

heat transfer that does not require atoms and molecules to physically touch in order to transfer energy.

Force

something applied to increase or decrease the kinetic energy of an object.

Mechanical energy waves

waves that can only move through a medium, or some kind of matter.

Earthquake waves

waves that move through the rock of Earth's crust and interior, transferring earthquake energy around the globe.

Sound energy

the vibration of air molecules as waves of energy move through them.

Radiation or radiant energy

wave energy that does not rely on matter to be transferred.

Emptiness of space

the area through which radiant energy can move without matter.

Radiant energy

exists as heat, visible light, UV rays, X-rays, and other forms of wave energy along the electromagnetic spectrum.

Wavelength

the distance from the top of one wave to the next and determines whether a wave is visible or invisible.

Laws of thermodynamics

the predictable rules that describe how energy behaves.

First law of thermodynamics (law of conservation of energy)

states that energy cannot be created or destroyed and is conserved. Energy must come from somewhere and must be added to a system as heat or work to create changes.

Second law of thermodynamics (law of entropy)

states that energy flows in one direction.

Entropy

the tendency of something to proceed in one direction.

Joule

a unit that measures energy or work required to move something across one meter while applying one newton of force.

Watts

the number of joules per second used to do work.

Calorie

a term people used before energy was scientifically defined as a joule.

100 watts

The average human being emits this amount of energy (approximately 0.02 calories per second).

2,000 kilocalories each day

The average amount of energy a person needs to consume to replace energy.

Biomass

the stored potential energy in plants and biological matter that fuels nearly every animal on Earth.