Transcript Chemical energy - Net Start Class

TAKS objective 4
Energy, Forces, and Motion
Middle School Science
Science TAKS Need to Know
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Energy
The ability to do
work or to cause
change
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Chemical Energy –
Energy transformations
Chemical energy – when light energy from the sun is converted to the
energy in the bonds of the sugar molecules formed in photosynthesis.
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Chemical Energy
Examples of chemical
energy changing into
heat energy:
Lighting a match
Burning a wood fire
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Heat energyEnergy transformations
Heat energy –
energy is absorbed
and temperature
rises.
Specific heat- the
ability of a substance
to absorb heat
energy
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Specifics of Specific Heat
Water Holds Thermal Energy
at Lower Temperature
Specific heat capacity of water is larger than soil,
so the rise of temperature is less for water, all
other things being equal. But, there's another
effect:
Sun's energy penetrates farther into water than
it does into earth, so the temperature rise per
square meter of exposed surface is less for
water.
Temperature is a measure of
the average kinetic energy
of the molecules in the object.
----------------------------------------Will both fingers feel the same
temperature when they're
put in the warm water?
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Electrical energyEnergy transformations
Electrical energy- flow of electrons (a current)
Other ways of generating electricity:
•Water flowing through a dam in a river to move
turbines
•Wind generators that use the energy of moving
wind & operate a generator
•Nuclear power plants convert atomic energy into
heat. Heat boils water to form steam & then
follows the same energy transformations as coal
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power plants Science TAKS Need to Know
Many energy transformations…
Electrical to mechanical:
Electricity used to spin the CD (Spinning CD has mechanical energy due
to its position or motion)
Electrical to sound:
A laser converts the digital information on the CD into electrical energy and
this energy goes to the headphones as a vibration- this transmits Sound!
Chemical to electrical:
Batteries store chemical compounds that react when they are used to
power something. This produces a flow of electrons which is electricity!!
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Sound energyEnergy transformations
Sound – consists of mechanical
energy waves created by vibrations.
Sound must travel through
something (called “medium” or
“media”) such as air, water, or a
solid.
The medium carries the energy of
the wave from one place to another.
Example: Air transmits the energy
of the vibrating material in the
headphones to your eardrums.
A vacuum is a space that contains little or no matter. Sound can’t
travel through a vacuum since there are no particles to squeeze
together (compression) or spread apart (rarefaction)
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Many times it takes a whole series of energy conversions to do a certain job.
For example, just to get the energy to make a piece of toast, there are several
energy conversions involved.
Chemical energy stored in coal is released as heat and light energy when the coal
is burned. The heat energy is used to produce steam and is changed into
mechanical energy in a generator. The generator converts mechanical energy into
electrical energy that travels through power lines into your home. When you use
your toaster, that electrical energy is again changed into heat energy.
Have you ever touched a light bulb when it was on? Or tried to change it when it
burnt out after being on? What you have discovered is the conversion process of
energy- When you turn on a light, not all of the electricity is converted to light
energy. Some of the energy is converted to heat.
Remember, energy is never lost- it’s only converted from one form to another.
This is the law
of conservation of energy
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Light waves do not
need a medium to
transmit energy! They
can even travel through
empty space.
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A wave is a disturbance that
transfers energy from one place
to another.
Water waves are
a form of a wave
that transmits
mechanical
energy across
the surface of
water.
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Seismic waves are caused by
earthquakes that transmit
mechanical energy through the
Earth’s layers.
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Potential (PE)
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Kinetic Energy (KE)
Energy due to
motion of an object
Did you know that
the gas burned in a
car engine is
chemical energy
being turned into
Kinetic Energy?
Rubber band flying
through the air has
kinetic energy
Speed & mass affect
kinetic energy–
Faster/heavier…more
Kinetic Energy
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Before the yo-yo begins its fall it has stored energy due to its
position. At the top it has its maximum potential energy. As it
starts to fall the potential energy begins to be changed into kinetic
energy. At the bottom its potential energy has been converted
into kinetic energy so that it now has its maximum kinetic energy
A waterfall has both potential and
kinetic energy. The water at the top
of Bridal Veil Falls has stored
potential energy. When the water
begins to fall, its potential energy is
changed into kinetic energy.
This change in energy also
happens at Niagara Falls where it
is used to provide electricity from
the transformation of mechanical
and electromagnetic energy.
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Energy Transformations
Potential energy
A rock sitting at the
top of a cliff
Roller coaster car at
the top peak of a
hill
A swimmer posed to
dive off the end of
a diving board
NO MOTION !!
Kinetic energy
A bouncing ball
A moving roller
coaster
A track star
running
A girl skiing
MOTION is the
key!!!!
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A book resting on a desk illustrates balanced forces. However, a book dropped
from a desk illustrates unbalanced forces. In this case, gravity has
overcome the balance of forces.
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You use force to move your body
When you bend your arm, your
muscles contract, which
applies force to your arm
bones. Your arm responds to
this force by moving.
During breathing, muscles
contract (use force) to move
air in and out of the lungs.
The heart contracts
(uses force) to pump
blood through the
blood vessels,
carrying oxygen to the
muscles.
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All living things use force to move
Emerging seedlings
exert force on the
surrounding soil.
This force pushes
the stem of the plant
out of the ground.
Plants exert
force to open
flower petals,
curl & uncurl
leaves &
push roots
through the
soil.
Force is used to
move materials
in & out of cells.
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Fish exert force to
swim by pushing
against the water.
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In order for a force to move something, it must be
an unbalanced force. This means that a force is
stronger in one direction than the forces in the
opposite direction.
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Acceleration of an object moving in one direction is
the speed (m/s) per unit of time (s), or change in speed
divided by time. The unit for acceleration is m/s2.
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Data can be
displayed &
interpreted in many
ways
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Force & motion are related
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What’s the advantage to knowing how much force we use
to do something???
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A lever is a bar that rests on a support
called a fulcrum which lifts or moves
loads.
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Types of levers
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This pulley has 1
wheel, so it
changes the
direction of pull 1
time. The input
force is the same
as the weight
using the pulley.
A pulley is a
simple
machine that
uses grooved
wheels and a
rope to raise,
lower or move
a load. When
a rope passes
over a wheel,
it changes the
direction of
effort (pull)
needed to
move the
load.
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Wedge
A wedge is an object with at least
one slanting side ending in a sharp
edge, which cuts material apart.
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An inclined plane is a ramp used to reduce the effort
needed to raise or lower an object over a vertical
height.
It is easier to climb stairs to get to a second floor than to
climb straight up a rope. It is easier to walk up a long,
gentle hill than to climb up a short, steep hill.
Examples of inclined planes:
Loading ramp; Stairs or wheelchair ramp
Mountain road; Threaded screw.
The ancient Egyptians used inclined planes, or ramps,
to move huge blocks of stone to build the pyramids.
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A screw is an inclined plane
wrapped around a pole
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Wheel & axle
A wheel with a rod, called
an axle, through its center
lifts or moves loads.
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