Transcript What is Energy?

Follow the Energy
Adapted from Scott Denning’s
presentation for the CSU CMMAP
course Summer 2007
By Jim Barnaby Summer 2008
Follow the Energy
An Overview of Energy’s Effect
on the Earth System
What is energy?
Potential & Kinetic Energy
Types of Energy
Conservation of Energy
Energy flows downhill from hot to cold
Effect of Energy on Matter (Molecular Motion)
Law of Conservation of Energy
What is Energy?
• What is Energy?
My 8th grade textbook says, “Energy is
not matter”
Matter is anything with mass & volume
Can we change matter into energy?
How?
Many textbooks now say:
Matter is Frozen Energy
Energy Can Come From Reactions
Mass can be converted into energy in nuclear
fission and fusion reactions. Fission and
fusion involve atomic nuclei and release
tremendous amounts of energy.
Einstein showed that if matter is destroyed,
energy is created and if energy is
destroyed, matter is created. The total
amount of mass and energy is conserved.
Defining Energy is Hard
“Energy is the ability to do work”
“Energy is the ability of something to cause
change”
(Physicists define work as “when force moves
an object”)
All work requires energy
Work and energy are the same thing
Energy is Currency
Energy is the universal
currency of life
—it causes change and
makes things happen
“Energy Changes
Make Things Happen”
Dave Watson, http://www.ftexploring.com
• Energy is a property or characteristic of
matter that makes things happen, or, in the
case of stored or potential energy, has the
"potential" to make things happen.
• Without energy, nothing would ever
change, nothing would ever happen. You
might say energy is the ultimate agent of
change, the queen mother of all change
agents.
Copyright 2000-2007. The Flying Turtle Company. All rights reserved
Kinetic Energy moves me
Kinetic Energy (KE)
Energy in the form of motion
Depends on mass and velocity of moving
object.
Object in motion has ability to do work.
“… They Said I had Potential”
Potential Energy (PE)
Stored energy due to position
Examples:
rock on a cliff, battery, food,
gasoline, stretched rubber band, apple growing
on a tree
Work is done on object to gain PE
Types of Energy
Five forms of energy:
Mechanical
Heat
Chemical
Electromagnetic
Nuclear
Conservation of Energy
• Energy can be stored
• Energy can move from one piece of matter
to another piece of matter
• Energy can be transformed from one type
of energy to another type of energy
• The First Law of Thermodynamics:
– During all this moving and transforming the
total amount of energy never changes.
Kinds of Energy
• Radiant Energy -- light
• Kinetic Energy -- motion
• Gravitational Potential Energy -- height
• “Internal Energy”
– Temperature, Pressure -- hot air
– Chemical energy
– Nuclear energy
• Conversions among different kinds of energy
power all that happens in the weather and
climate!
If Energy is Conserved …
then why do we need to “conserve energy?”
• Total energy is conserved (First Law), but not its
usefulness!
• Second Law of Thermodynamics:
Energy flows “downhill” from highly concentrated
(hot) forms to very dilute (cold) forms
• Gasoline burned in your car
(hot) makes it move
• Turbulence and friction of
tires on road dissipated as
heat
• Heat radiated to space (cold)
Energy Makes
Things Happen
Hurricane Katrina Devastation in Biloxi, Mississippi
August 29, 2005
Energy’s Effect on Molecules
How does heat energy effect atoms and
molecules within matter?
Heat energy (hot) speeds up molecular
motion
Lack of heat energy (cold) slows down
molecular motion
Everything obeys this law
The law of Conservation of Energy:
Energy cannot be created or destroyed. It may
be transformed from one form into another;
however, the total amount of energy in the
universe remains constant. (Transformers)
Energy conversions occur without a gain or loss in
energy
Due to friction, energy might seem to be lost, but it
has changed into thermal energy.
It all Starts with the Sun
• Nuclear fusion in the Sun
powers all changes on the Earth!
• Solar energy heats the air, lifts
it, blows it around, evaporates
water, makes snowstorms
• Conversion of solar energy and
downhill dissipation as heat
energy drive all weather and
climate phenomena
• Energy comes in hot, and goes
out cold
Planetary Energy Balance
Energy In = Energy Out
What’s Missing?
• Vertical structure
The “greenhouse effect”
• Energy storage and transport
The “general circulation” of the atmosphere and
oceans
Vertical Structure is Crucial
• The world is a big place, but the
atmosphere is very thin, and most of it is
close to the ground
– About 15% of the atmosphere is below our feet
– At the top of Long’s Peak, the figure is 40%
– You are closer to outer space than you are to
Colorado Springs!
• Changes in atmospheric temperature with
height are responsible for the
“Greenhouse Effect,” which keeps us from
freezing to death
Vertical Thermal Structure
• Heated from
below by latent
and sensible
heat fluxes
• Heated in
stratosphere
by ozone
absorption
The Job of the Atmosphere
is to let the energy out!
“Piles up” in tropics
“Escapes” near poles and aloft
The movement of the air (and oceans) allows energy to be
transported to its “escape zones!”
Energy Reservoirs (Stored Energy)
Ocean
Atmosphere
• The oceans are
about 4,000 m
(12,000 ft) deep
• The top 10 m (30 ft)
equal the mass of
the atmosphere
• The top 3 m (9 ft)
equal the heat
capacity of the
atmosphere!
The state of the oceans determines the climate
on time scales of thousands to millions of years!