What Is Energy?
Forms of Energy
Energy forms are either potential or kinetic. Potential
energy comes in forms that are stored including chemical,
gravitational, mechanical, and nuclear. Kinetic energy is
energy in movement and includes electrical energy, heat,
light, and sound.
Forms of Energy Basics
What is energy?
Scientists define energy as the ability to do work. Modern civilization is possible because people have learned how to
change energy from one form to another and then use it to do work. We use energy to move cars along roads and boats
through water, to cook food on stoves, to make ice in freezers, and to light our homes.
Forms of energy
Many forms of energy exist, but they all fall into two basic categories:
● Potential energy
● Kinetic energy
Sources of Energy
We use many different energy sources to do work. Energy sources are called renewable or nonrenewable. Renewable
and nonrenewable energy are used as primary energy sources.
Nonrenewable energy sources
In the United States, nonrenewable energy sources supply most of the energy we use. Nonrenewable energy sources
include coal, natural gas, petroleum made from crude oil and natural gas liquids, and uranium. These energy sources are
called nonrenewable because their supplies are limited and take a very long time to form. Coal, crude oil, and natural gas
formed from the remains of plants buried underground millions of years ago.
Name/Period_________________/_______
Renewable energy sources
Renewable energy sources include biomass, geothermal energy, hydropower, solar energy, and wind energy. They are
called renewable because they are naturally replenished in a short period of time. Day after day, the sun shines, the wind
blows, and rivers flow.
Potential energy
Potential energy is stored energy and the energy
of position.
Kinetic energy
Kinetic energy is the motion of waves, electrons,
atoms, molecules, substances, and objects.
Chemical energy is energy stored in the bonds
of atoms and molecules. Batteries, biomass,
petroleum, natural gas, and coal are examples of
chemical energy. Chemical energy is converted to
thermal energy when people burn wood in a
fireplace or burn gasoline in a car's engine.
Mechanical energy is energy stored in objects
by tension. Compressed springs and stretched
rubber bands are examples of stored mechanical
energy.
Nuclear energy is energy stored in the nucleus
of an atom—the energy that holds the nucleus
together. Large amounts of energy can be
released when the nuclei are combined or split
apart.
Gravitational energy is energy stored in an
object's height. The higher and heavier the
object, the more gravitational energy is stored.
When a person rides a bicycle down a steep hill
and picks up speed, the gravitational energy is
converting to motion energy. Hydropower is
another example of gravitational energy, where
gravity forces water down through a hydroelectric
turbine to produce electricity.
Radiant energy is electromagnetic energy that
travels in transverse waves. Radiant energy
includes visible light, x-rays, gamma rays, and
radio waves. Light is one type of radiant energy.
Sunshine is radiant energy, which provides the
fuel and warmth that make life on earth possible.
Thermal energy, or heat, is the energy that
comes from the movement of atoms and
molecules in a substance. Heat increases with
increases in the speed that these particles move.
Geothermal energy is the thermal energy in the
earth.
Motion energy is energy stored in the movement
of objects. The faster they move, the more energy
is stored. It takes energy to get an object moving,
and energy is released when an object slows
down. Wind is an example of motion energy. A
dramatic example of motion energy is a car
crash—a car comes to a total stop and releases
all of its motion energy at once in an uncontrolled
instant.
Sound is the movement of energy through
substances in longitudinal
(compression/rarefaction) waves. Sound is
produced when a force causes an object or
substance to vibrate. The energy is transferred
through the substance in a wave. Typically, the
energy in sound is smaller than in other forms of
energy.
Electrical energy is delivered by tiny charged
particles called electrons, typically moving
through a wire. Lightning is an example of
electrical energy in nature. However, most
electrical energy is from combustion of a fossil
fuel or from conversion of a different type of
energy such as chemical, radiant, or nuclear.
Name/Period_________________/_______
Laws of Energy
Energy is neither created nor destroyed
To scientists, conservation of energy does not mean saving energy. Instead, the law of conservation of energy says that
energy is neither created nor destroyed. When people use energy, it doesn't disappear. Energy changes from one form of
energy into another form of energy.
A car engine burns gasoline, converting the chemical energy in gasoline into mechanical energy. Solar photovoltaic cells
change radiant energy into electrical energy. Energy changes form, but the total amount of energy in the universe stays
the same.
Scientists at the U.S. Department of Energy think they have discovered a mysterious new form of energy called "dark
energy" that is actually causing the universe to grow!
Converting one form of energy into another
Energy efficiency is the amount of useful energy obtained from a system. A
perfectly energy-efficient machine would convert all of the energy put into the
machine to useful work. In reality, converting one form of energy into another
form of energy always involves a conversion into useable (or useful energy)
and unusable (or unuseful) forms of energy.
Most energy transformations are not efficient. The human body is a good
example. The human body is like a machine, and the fuel it requires is food.
Food gives a person energy to move, breathe, and think. However, the
human body isn't very efficient at converting food into useful work. The
human body is less than 5% efficient most of the time. The rest of the energy
is converted to heat, which may or may not be useful, depending on how cool
or warm a person wants to be. You can really feel that heat when you
exercise!
Name/Period_________________/_______
Name/Period_________________/_______
Energy Questions
1. What is energy?______________________________________________________________
2. What are the two categories of energy?_____________ & ________________
3. List an example of each of the four types of potential energy
types
Example
Renewable or Nonrenewable
Chemical
mechanical
nuclear
Gravitational
4. List an example for each of the types of kinetic energy and if it is renewable or nonrenewable.
Type of Energy
Example
Renewable or Nonrenewable
Radiant
Thermal
Motion
Sound
Electrical
5. What category would wind fit into and why (this is not in the article you have to think and
justify)?_____________________________________________________________________
___________________________________________________________________________
6. What category would ocean waves fit into and why (think critically)? ___________________
___________________________________________________________________________
7. What is the difference between renewable and nonrenewable energy?___________________
___________________________________________________________________________
8. What does the law of conservation of energy say?___________________________________
___________________________________________________________________________
9. According to the article, most forms of energy conversion are NOT efficient. Based on this
knowledge where does the majority of energy that we eat go? ___________________
10.According to the consumption table, what fuel source was used most commonly? __________
11. Is this fuel renewable?_______ What will do in a few generations? (answer on the back)
