KEY CONCEPT
Energy can change forms
but is never lost.
STANDARDS
6–5.2 Explain how energy can be transformed
from one form to
another (including the
two types of mechanical
energy, potential and
kinetic, as well as chemical and electrical energy) in accordance with
the law of conservation
of energy.
BEFORE, you learned
NOW, you will learn
• Energy causes change
• Energy has different forms
• Kinetic energy and potential
energy are the two general
types of energy
• How energy can be converted
from one form to another
• About the law of conservation
of energy
• How energy conversions may
be inefficient
THINK ABOUT
How does energy
change form?
Potential energy is stored in the
chemicals on the head of a match.
The flame of a burning match
releases that energy as light and
heat. Where does the energy to strike
the match come from in the first place?
VOCABULARY
law of conservation
of energy p. 362
energy efficiency p. 363
Energy changes forms.
A match may not appear to have any energy by itself, but it does contain potential energy that can be released. The chemical energy stored
in a match can be changed into light and heat. Before the chemical
energy in the match changes forms, however, other energy conversions
must take place.
MIND MAP
Use a mind map to take
notes about how energy
changes forms.
Plants convert energy from the Sun into chemical energy, which is
stored in the form of sugars in their cells. When a person eats food that
comes from plants—or from animals that have eaten plants—the person’s cells can release this chemical energy. Some of this chemical energy
is converted into the kinetic energy that a person uses to rub the match
over a rough surface to strike it. The friction between the match and
the striking surface produces heat. The heat provides the energy needed
to start the chemical changes that produce the flame. From the Sun to
the flame, at least five energy conversions have taken place.
check your reading
358 Unit 3: Energy and Machines
How is a person’s chemical energy changed into another form of
energy in the lighting of a match?