Download lesson-2-explore-page-97-energy-transformations

Middle School Science
Room 212 – Miss Lida
Lesson 2 / Explore – Page 97
“Energy Transformations and Work”
Energy Transformations
 Energy transformation is the conversion of one form of energy to another.
 Energy is also transferred when it moves from one object to another.
Energy Conservation
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The Law of Conservation of Energy – states that energy can be transformed from one
form to another, but it cannot be created or destroyed.
Roller Coasters
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Most roller coasters start by pulling you up to the top of a big hill. When you go up a hill,
the distance between you and Earth increases and so does your potential energy.
You then race downhill, moving faster and faster. The gravitational potential energy is
transformed to kinetic energy.
At the bottom of the hill the kinetic energy is transformed back to gravitational potential
energy as you move up the next hill.
Plants and the Body
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When a plant carries on photosynthesis, it transforms radiant energy from the Sun into
chemical energy.
The energy is stored in the bonds of the plant’s molecules.
When you eat broccoli for example, your body breaks apart the chemical bonds in the
molecules that make up broccoli. This releases chemical energy that your body
transforms to energy it needs, such as energy for movement, temperature control, and
other life processes.
Electric Energy Plants
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When electric energy plants burn fossil fuels, they transform the chemical energy from
the molecules that were made by plants that lived millions of years ago.
The chemical energy is then transformed to the electric energy that you use in your
home and school.
Energy and Work
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Work is the transfer of energy that occurs when a force makes an object move in the
direction of the force while the force acts on the object.
To do work on an object, an object must move in the direction of the force. Work is
done only while the force is moving the object.
Doing Work
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Work depends on the amount of force applied to an object.
Work also depends on the distance the object moves during the time the force is
applied.
Calculating Work
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The equation for work is:
Work (in joules) = force (in newtons) x distance (in meters)
W = Fd
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The force in the equation is in newtons (N), and the distance is in meters (m). The
product of newtons and meters is newton-meter (N●m). A newton-meter is also called
a joule (J).
Energy and Heat
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In every energy transformation and every energy transfer, some energy is transformed
into thermal energy. This thermal energy is transferred to the surroundings.
Thermal energy moving from a region of higher temperature to a region of lower
temperature is called heat.
Scientists sometimes call this heat waste energy because it is not easily used to do
useful work.