Science, Matter, and Energy - Environmental Science - page 29

Another type of moving energy is heat: the total
kinetic energy of all moving atoms, ions, or molecules
within a given substance, excluding the overall motion
of the whole object. When two objects at different tem-
peratures contact one another, kinetic energy in the
form of heat flows from the hotter object to the cooler
object.
In electromagnetic radiation, another type of mov-
ing or kinetic energy, energy travels in the form of a
wave as a result of the changes in electric and magnetic
fields. Many different forms of electromagnetic radia-
tion exist, each having a different wavelength (distance
between successive peaks or troughs in the wave) and
energy content, as shown in Figure 2-8. Such radiation
travels through space at the speed of light, which is
about 300,000 kilometers per second (186,000 miles per
second). Visible light makes up most of the spectrum
of electromagnetic radiation emitted by the sun (Fig-
ure 2-9, p. 30).

2-3 ENERGY

What Is Energy?
Energy is the work needed to move matter and the
heat that flows from hot to cooler samples of matter.
Energy is the ability to do work and transfer heat. Us-
ing energy to do work means moving or lifting some-
thing such as this topic, propelling a car or plane,
warming your room, cooking your food, and using
electricity to move electrons and light your room. The
sun provides our planet with light and heat and pro-
vides plants with energy to produce the chemicals
they need for growth. Animals get the energy they
need from the chemical energy stored in the plant and
animal tissue they eat. When you eat, your body trans-
forms the energy stored in food into energy to do the
work you need to stay alive, move, and think.
Energy exists in a number of different forms: elec-
trical energy from the flow of electrons, mechanical en-
ergy used to move or lift matter, light or radiant energy
produced by sunlight and electric light bulbs, heat
when energy flows from a hot to a colder body, chemi-
cal energy stored in the chemical bonds holding matter
together, and nuclear energy stored in the nuclei of
atoms. These and other types of energy can be classi-
fied into two types based on whether they are moving
energy (called kinetic energy) or stored energy (called
potential energy).
Matter has kinetic energy because of its mass and
its speed or velocity. Examples of this energy in motion
are wind (a moving mass of air), flowing streams, heat
flowing from a body at a high temperature to one at a
lower temperature, and electricity (flowing electrons).

Find out how color, wavelengths, and energy intensities of
visible light are related at Environmental ScienceNow.

Besides moving energy, the other type of energy
is potential energy, which is stored and potentially
available for use. Examples of stored or potential en-
ergy include a rock held in your hand, an unlit match,
still water behind a dam, the chemical energy stored
in gasoline molecules, and the nuclear energy stored in
the nuclei of atoms.
Potential energy can be changed to kinetic energy.
Drop this topic on your foot, and the topic's potential
energy when you held it changes into kinetic energy.

Sun

Ionizing radiation

Nonionizing radiation

Far
ultraviolet
waves

Near
ultraviolet
waves

Near
infrared
waves

Far
infrared
waves

Cosmic
rays

Gamma
rays

Visible
waves

TV
waves

Radio
waves

X rays Microwaves

10 -14
High energy, short
wavelength

10 -12 10 -8 10 -7 10 -6 10 -5 10 -3 10 -2 10 -1 1

Wavelength in meters
(not to scale)

Low energy, long
wavelength

Active Figure 2-8 The electromagnetic spectrum: the range of electromagnetic waves, which differ in wave-
length (distance between successive peaks or troughs) and energy content. See an animation based on this
figure and take a short quiz on the concept.