Download Energy Unit Packet energy_unit_packet

ENERGY
Name ______________________
Energy is the ability to do work. Work is the ability to exert a force over a distance. Work
is done when force moves an object in the direction of that force. Energy is one of two
basic concepts of physics. Physics is the study of matter and energy. The word “physics”
comes from a Greek word meaning nature. Physics explains sound to musicians, color to
artists, and speed to race car drivers.
When Herman lifts this barbell, he is applying
an upward force. The distance the barbell
moved is measured from its resting place on
the floor to the position over Herman’s head.
In order for Herman to apply the lifting force,
he must use energy.
Kinds of Energy
We will study two kinds of energy: potential and kinetic
Potential Energy
Energy isn't always moving. Potential energy is stored energy at rest. Potential energy
means that the system could do work but isn't doing so at the moment. There are many
different examples of potential energy. For instance, a stretched rubber band or a
compressed spring are ready to snap back, exerting a force over distance as they do so. A
ton of water at the top of a waterfall has the potential to do a certain amount of work as it
tumbles to the bottom. But, when the water has crashed onto the rocks at the bottom of the
fall, its work potential has been used up.
Potential energy is energy waiting to be unlocked.
Herman’s barbell now has potential energy. If he were to drop it, the
barbell would exert a force of its own. Look out Herman!
Kinetic Energy
When energy makes things move it is called kinetic energy. A rotating wheel, a speeding
car, a falling leaf - all do work, therefore they possess kinetic energy. Heat is a special kind
of kinetic energy - the kind associated with atoms in motion. Sound is caused by the
atoms and molecules bumping into each other as waves. We hear sounds because our
eardrums vibrate in response to moving air molecules. Mechanical force is the form of
energy we use to do work - to push, pull, or lift objects from one place to another.
Oh, oh! Herman dropped his barbell. The barbell now has
kinetic energy because it is moving. Herman is moving, too.
Energy can take several forms. This mnemonic may help you remember the six forms of
energy.
SCREAM-
sound
chemical (Includes Food energy)
radiant (heat and light. We will treat these as separate energy forms in this unit.)
electrical
atomic (only covered briefly in this unit)
mechanical (motion)
These forms are all interchangeable. They can be transformed (changed) into different
forms. Chemical energy can be changed into heat by burning a fuel. Heat can be
transformed into mechanical energy in an engine. Mechanical energy can be transformed
into electrical energy by a generator. An electric light bulb produces light. An electric range
produces heat. A radio emits sound energy, and a fan converts electrical energy into
mechanical energy, heat energy, and sound energy. During these transformations, the
total amount of energy after the change is the same as the amount before the change.
Energy cannot be destroyed or created. This is the Law of Conservation of Energy or
the First Law of Thermodynamics .
A light bulb transforms electrical energy into light and heat energy.
Energy from burning gasoline transforms from the chemical energy in
the fuel into intense heat energy. The engine then transforms the heat
energy into mechanical energy that makes the car move.
The Second Law of Thermodynamics states that transformation always leads from more
useful energy to less useful forms. For example, when you burn coal or gas, some of the
high-grade energy is lost as heat to the atmosphere where it cannot be recovered to do
work.
Energy Efficiency refers to the amount of energy lost during transformation. A more
efficient conversion process means that less energy is lost as heat than would be lost
through a less efficient process.
Transferring Energy
Energy can be moved from one object to another object. For example, a stove burner
transfers heat to a frying pan, which then transfers heat to the oil, which then transfers
heat to the food. Also, a moving baseball transfers mechanical energy to the catcher’s mitt.
Energy Transfer is like a bus transfer. Here Sally Smart is transferring
from one bus to another. Sally is like energy being transferred: she is
moving from one place to another but is still the same Sally.
Forms of Energy
Draw one form of energy in each space. Some of your illustrations may use more than one
form of energy. Label each form of energy.
Light (Radiant)
Heat (Radiant)
Sound
Motion/Mechanical
Chemical (Food)
Electrical
Chemical to Heat and Light (Radiant)
A) Match
Watch as the teacher lights a match. What did you observe?
How was energy transformed, or converted—what forms of energy were involved and how
did they change?
B) Hand Warmer.
Hold the hand warmer. Describe its temperature.
After the pack is activated, feel it again. Describe its temperature. What does the inside
feel like now?
What energy transformations just occurred?
Light Energy to Food Energy
Leaves of plants like trees and grass transform light energy from the sun into food energy
(a special type of chemical energy).
Electricity to Radiant
Electricity is the flow of electrons from a source and through a circuit. Electrons are tiny
negatively-charged particles orbit the nucleus of an atom. These electrons can move from
one atom to another.
Observe the temperature and color of an incandescent light bulb while it is turned off.
Describe your observations.
After the bulb is turned on, what do you observe about it? What energy transformations
took place?
Motion (Mechanical) to Electricity
Rub an inflated latex balloon in your hair. What do you notice about your hair?
You caused a charge of static electricity to build up in your hair. This was caused by the
motions you made as you rubbed the balloon. Static electricity is electricity that is not
moving. This is different than the electricity in your wall outlet. Electricity that powers your
lights and your television is called current electricity. It moves through a circuit like a
current of water moving through a pipe. Static electricity is more like a puddle.
We generate this current electricity by passing a massive coil of wire through a magnetic
field. You have probably experienced magnetic fields whenever you played with magnets.
To move this huge coil of wire requires mechanical energy. This can come from steam
produced by coal fires, gas fires, nuclear power, or it can come from hydroelectric power
(water falling and turning turbines on its way down), wind power and other sources. A
turbine is the machine that encounters the mechanical force and gets turned or rotated by
that force. It often has large paddle-like structures on it that water strikes. The turbine is
connected to that huge coil of wire.
Friction (mechanical) to Heat
Rub your hands together. What do you notice?
Rub your hands on a carpet. What happens to your hand?
Put soapy water in your hands and rub them together again. Did they feel the same as
they did without the soap? Explain the difference if any.
Friction transforms motion (mechanical) energy into heat. The soap was a lubricant that
reduced the friction.
How can you use this information to solve the friction problem in a car engine that has lots
of moving parts rubbing together?
Conduction is the transfer of heat energy through a substance. Heat energy is the motion
of atoms and molecules. Moving atoms and molecules bump into their neighbors, causing
them to move too.
The metal fork conducts or carries the
heat from the flame to the hand. Always
be very careful around heat sources.
The heat energy from the flame travels along this metal rod.
A pan on a stove conducts heat from the burner to the liquid in the pan. On an electric
stove, electrical energy is converted in to heat and _____________.
Heat energy also moves toward the cook’s hand. What prevents the hand from being
burned?
An insulator is a material that does not conduct heat very well. Wood, some plastics, and
certain cloth materials are good insulators. They do not conduct heat as quickly or as
efficiently as does metal. They can still get very hot over time, though, so be careful.
This insulator slows the conduction of heat energy from the metal rod.
Sound Energy
If you pluck a tightly stretched rubber band, you may notice a sound. If you look closely at
the rubber band as it makes a sound, what do you see?
Dip your finger into the surface of some water in a tray. What happens to the water surface
as a result of your finger touching it?
Sound is actually just vibrations transferred through the air as waves to our ears. What
form of energy was transformed into the sound energy as the band was plucked?
List four objects or devices that transform some form of energy into sound energy. If you
need help, think about musical instruments. Draw a picture for one of them that shows
what is happening. Then, explain it with words.
1.
2.
3.
4.
Some Renewable Energy Sources
A renewable energy source is any means to generate power that can be used again and
again without having to produce more fuel.
Solar power from the sun is renewable, because the sun is always producing more. The
suns radiant energy strikes special plates called solar cells. These plates emit electrons,
which eventually flow through a circuit. Solar energy also can be used to heat water for
energy purposes.
Geothermal power comes from the tremendous heat that the Earth continuously
generates. We can place water pipes into this heat, and the heat will turn the water into
steam that can turn turbines. Hot water can also be pumped from the ground to heat
homes.
3) steam or hot water can turn
turbines or can heat buildings.
1) Water is pumped into the pipe.
2) Magma heats the surrounding water and
transfers this heat energy to the water in the
pipe.
Wind is the movement of air that is caused by unequal heating and cooling of the Earth’s
surface. Wind can turn turbines as well. Wind has pushed sail boats and ships around for
centuries before engines were invented,
Tidal power harnesses the energy form the incoming and outgoing tides. As the tide rises,
water flows inward towards the land. As the tide falls, water flows towards the sea. This
power can turn turbines to generate electricity.
Tide coming in turns the wheel turbine
Nuclear or atomic power captures the enormous heat given off by atoms as they split
apart into smaller atoms. We use Uranium 235 and plutonium for this form of power. They
are large atoms that break apart easily. The heat turns water to steam that turns turbines.
Gas, coal, and oil come from dead organisms that lived millions of years ago. As these
organisms were buried by sediments, they became exposed to great heat and pressure.
These forces changed the creatures’ bodies into what we call fossil fuels. This takes a
great deal of time—millions of years. Knowing this, are gas, oil, and coal considered
renewable sources? Why or why not?
Complete the web diagram
with the forms of energy you
have studied. Do you notice how
interconnected energy forms are?
Complete the energy chain below.
Sunlight helps a
tree produce and
store food.
Light energy to
Food energy (a
type of chemical
energy)
Wood from the
tree is burned in
the firebox of a
steam engine.
The steam
engine propels
a train
locomotive.
The engine
generates
electricity.
Food/Chemical
_____________energy
____________energy
_______energy
to
to
to
____________energy
___________energy
energy
to
_________energy
_____________energy
transforms mechanical energy
transformation.
WORD BANK
tidal
engine
radiant
nonrenewable
kinetic
insulator
efficiency
generator
turbine
electron
renewable
conductor
nuclear
solar
work
geothermal
potential
energy
Name _________________________ Date______________
Energy Test
Fill in the blanks with words from the word bank. Note: not all of the words will be used.
(1 pt each)
1. Stored energy at rest is called ______________________________ (what kind of) energy.
2. _______________ refers to the amount of energy lost during conversion.
3. The_____________________________ states that energy can neither be created nor
destroyed, but that it can be converted from one form to another.
4. A generator converts _________________ energy into electrical energy.
5. ___________ energy includes both heat and light forms.
6. A car rolling down a hill is an example of __________________ (what kind of) energy.
7. ___________ is the ability to exert a force over a distance.
8. Geothermal energy is an example of a ________________________ energy source.
9. When you strum a guitar string, you change mechanical energy into ____________energy.
10. Wax melting on the end of a metal rod when a flame is applied to the opposite end is an
example of ________________.
Word Bank
Kinetic
Radiant
Chemical
Atomic
Sound
Efficiency
Potential
Work
Mechanical
Nonrenewable
Renewable
Conduction
Law of Conservation of Energy
2nd Law of Thermodynamics
11. You turn on an electric motor. Use pictures and/or words to describe three energy
conversions that are taking place. Remember to consider all the forms of energy that
the electricity may be converted into. (3 pts)
12. Construct an energy chain below by drawing examples of energy conversions
involving three different forms (heat, mechanical, chemical, etc.). (3 pts)
Converting Energy Crossword Word bank Transparency
Tidal
Engine
Radiant
Nonrenewable
Kinetic
Insulator
Efficiency
Generator
Turbine
Electron
Renewable
Conductor
Nuclear
Solar
Work
Geothermal
Potential
Energy