Introduction
Energy is defined simply by scientists as the
capacity for doing work.
Matter is the material (atoms
and
molecules) that constructs things on the
Earth and in the Universe. Albert Einstein suggested
early in this century that energy and matter are related
to each other at the atomic level. Einstein theorized
that it should be possible to convert matter into
energy. From Einstein's theories, scientists were able
to harness the energy of matter beginning in the 1940s
through nuclear
fission.
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A D V E R T I S E M E N T
The most spectacular example of this
process is a nuclear explosion from an atomic bomb. A
more peaceful example of our use of this fact of nature
is the production of electricity from controlled fission
reactions in nuclear reactors. Einstein also suggested
that it should be possible to transform energy into
matter.
Energy and matter are
also associated to each other at much larger scales of
nature. Later on in this chapter, we will examine how
solar radiation provides the energy to create the matter
that makes up organisms. Organisms then use some of this
matter to power their
metabolism.
Types of Energy
Energy comes in a
variety of forms. The simplest definition of the types
of energy suggests that two forms exist:
kinetic energy and
potential energy. Kinetic energy is the
energy due to motion. A rock falling from a cliff, a bee
in flight, wind blowing leaves of trees, and water
following over a waterfall are all examples of kinetic
energy. Potential energy is the energy stored by an
object that can be potentially transformed into another
form of energy. Water stored behind a dam, the chemical
energy of the food we consume, and the gasoline that we
putting in our cars are all examples of potential
energy. Conversion of this energy occurs when the energy
in food is used by an organism to energize its
metabolism, when the water in the dam flows through
turbines to produce electricity from motion, and when
the gasoline is used in a engine to produce motion from
combustion.
Some other forms of
energy include heat, electricity, sound, energy of
chemical reactions, magnetic attraction, energy of
atomic reactions, and light. Definitions for a few of
these types of energy are as follows:
Radiation - is the emission of energy
from a material object in the form of
electromagnetic waves and
photons.
Chemical Energy - is the energy
produced or consumed in chemical reactions.
Atomic Energy - is the energy
released from an atomic nucleus because of a
change in its subatomic
mass.
Electrical Energy - is the energy
produced from the force between two objects
having the physical property of electrical
charge.
Heat Energy - is a form of energy
created by the combined internal motion of
atoms in a substance.
On Earth, there are
fundamentally only three ways in which energy can be
transferred from one place to another:
conduction,
convection, and
radiation.
Conduction involves the adjacent transfer of
heat energy from one atom to another through the mass of
a gas, liquid, or solid. Condution results in the
continuous flow of heat energy along a temperature
gradient from areas of higher to lower temperature.
Convection involves the transfer of heat
energy by way of mass movements of a substance in gas or
liquid form in a vertical direction (horizontal transfer
is called
advection). Convection is often seen as
rising masses of gas or liquid called
convection currents. It is important to note
that energy transfer by way of conduction and convection
depends on the presence of matter. These forms of energy
transfer do not operate in the vacuum of space.
Radiation is the only means of energy
transfer that can occur across outer space. The transfer
of radiation produced at the Sun's surface through space
supplies the Earth with most of its energy.
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