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Forms of Energy
Mechanical Energy
Mechanical Energy is the energy an object
possesses due to its motion or position. For
example, a thrown baseball is in motion. On
the other hand, a brick held in your hand has
stored mechanical energy that would turn into
motion if you dropped it. So, mechanical
energy is both potential and kinetic energy.
Examples of mechanical energy: Because so
many objects are in motion (or could be in
motion), there are literally billions of examples.
Electric motors, jet engines, car engines, and
windmills are examples of kinetic mechanical
energy used by humans. Objects in nature that
are in motion, and therefore have kinetic
mechanical energy, include wind, tides, and
waves.
Chemical energy
Chemical Energy is energy stored in the bonds
between atoms. Batteries, gasoline, coal, and
sugar have stored chemical energy that people
can use. Since it is stored, it is a form of
potential energy.
Chemical reactions involve rearranging atoms.
Usually, once chemical energy is released from
a substance, that substance is transformed into
an entirely new substance. For example, when
vinegar reacts with baking soda, they turn into
sodium acetate, water, and carbon dioxide.
Chemical reactions that produce heat are called
exothermic reactions. Exothermic reactions
make their surroundings warmer by transferring
heat. Chemical reactions that absorb heat are
called endothermic reactions. An endothermic
reaction makes the surroundings cooler by
absorbing heat from them.
Examples of chemical energy: The chemicals in
fireworks store chemical energy in the bonds
between their atoms. When a firework
Adapted from: Forms of Energy, US Energy Information Administration, 2014.
detonates, chemical energy stored in it is
transferred to the surroundings as
thermal energy, sound energy and
kinetic energy. When this happens, the atoms
in the firework are rearranged and become new
substances.
1
2
3
Chemical energy is stored in the bonds between atoms.
Wood stores chemical energy in the bonds
between its atoms. As it burns, the atoms are
rearranged to form new chemicals. Chemical
energy is released and converted to thermal
energy (heat) and light energy. Then the wood
turns into ash, water, and gases (new
substances).
Electrical energy
Electrons are tiny particles that orbit the
nucleus of an atom. Humans can force
electrons along a path from one place to the
other. For example, in a copper electrical wire
electrons are forced from one copper atom to
the next, and so on. Electrical energy is energy
from moving electrons. Since the electrons are
moving, electrical energy is a form of kinetic
energy.
There are special materials, called conductors,
that allow electrons to flow through them.
Copper and aluminum are good conductors.
Some materials do not allow electrons to flow
easily through them, and they are called
insulators. Glass and rubber are good
insulators.
An electrical current occurs when electrons are
pushed, sort of like the current of a stream
pushes a floating stick. The current forces
electrons to move through a wire until they
reach an electrical appliance like a light bulb.
because it is so much larger than a cup of
coffee. Therefore, temperature is simply how
hot or cold an object is, measured in degrees.
Heat is the transfer of thermal energy from one
object to another.
Electrical current "pushes" electrons from atom to atom in a
Examples of thermal energy: Heat always
flows from hotter objects to cooler ones. If you
hold a warm penny, thermal energy will flow
from the penny to your hand. The atoms in the
penny would start to vibrate more slowly, and
the atoms in your skin would start to vibrate
more quickly. Thermal energy would continue
to flow from then penny to your hand until both
your hand and the penny were the same
temperature.
copper wire
Examples of electrical energy: Electrical energy
is formed when chemical energy from a battery
is used to push electrons along a copper wire.
When the electrical energy reaches a light bulb,
it is transformed into radiant energy (light) and
thermal energy (heat). In the same way,
electrical energy travelling through a wire in
your house to a blender is transformed into
motion energy, thermal energy (heat), and
sound energy.
Thermal Energy
Matter is made up of atoms. These atoms
move (or vibrate) constantly. Atoms vibrate
faster in hot objects and slower in cold objects.
Thermal energy is energy from vibrating atoms.
The hotter the substance, the more its
molecules vibrate, and the therefore
efore the higher
its thermal energy. Since thermal energy
involves atoms in motion, it is a form of kinetic
energy.
There is a difference between heat and
temperature. Think about a cup of water and a
swimming pool. They may both have a
temperature of 78o Fahrenheit, but obviously
the swimming pool has much more energy
Adapted from: Forms of Energy, US Energy Information Administration, 2014.
Thermal energy flows from a light bulb to the
air in the room. When the light bulb is turned
off, the thermal energy continues
ntinues to flow until
the light bulb is the same temperature as the
air. Then it no longer feels warm.
Electromagnetic energy
Electromagnetic energy is emitted from objects
as waves. Forms of electromagnetic energy
include radio waves, microwaves, visible light,
and x-rays.
Electromagnetic waves travel at the speed of
light, which is 186,000 miles per second.
Therefore, a radio wave could circle the Earth
almost eight times in one second, and light
travels 93 million miles from the Sun to the
Earth in only nine minutes. Because
electromagnetic waves are moving, they are a
form of kinetic energy.
Electromagnetic energy can travel through the
air, solids, and liquids. In addition,
electromagnetic energy can travel through
space. If it couldn't , sunlight would never reach
the Earth!
Examples of electromagnetic energy:
Microwaves are the shortest electromagnetic
waves. They bounce around inside the
microwave, causing water molecules in the food
to start vibrating billions of time each second,
transforming the electromagnetic energy into
heat energy.
Radar waves 1) are
emitted by the radar
transmitter, 2) reflect
off of the aircraft, and
3) travel back to the
radar receiver.
Radar waves are energy that is emitted from a
special transmitter. The radar waves reflect off
objects, and the reflected waves travel back to
the receiver.
Nuclear Energy
Nuclear energy is energy stored in the nucleus,
or center, of atoms. Because nuclear energy is
stored energy it is a form of potential energy.
During nuclear fission, atoms are split apart to
form new elements. In nuclear fusion, atoms
are fused together to form a new element.
Both processes release tremendous amounts of
energy.
An example of nuclear energy: In a nuclear
reactor, atoms of uranium are split and
become atoms of barium and krypton. This
releases tremendous amounts of energy. Heat
released during nuclear fission is used to turn
water into steam to run electrical generators.
Uranium fission
Adapted from: Forms of Energy, US Energy Information Administration, 2014.