ENERGY CHANGES MAKE THINGS HAPPEN
A simple definition of energy; Energy changes and transformations make things happen; Some
examples of energy changes making things happen; Stored Solar Energy is the fuel for most living
organisms and human made machines; a little bit about Energy and Heat Flow; Some different types of
Energy; the First Law of Thermodynamics and other intriguing things you should know about energy; a
final example of monkey's, bananas, and energy conversions.
For anything to happen there
always has to be an energy
conversion or change.
An example of Some of the Energy
Changes that have to happen in
order for a person to Jump are
given below:
It always starts
in the sun, where
matter is changed
into
electromagnetic
energy and zips
out into space. The
energy a person
uses to jump
always comes first
from the sun.
A tiny bit of the sun's energy falls
onto earth. On earth some of the solar
energy is changed by photosynthesis
into chemical energy stored in the
carbohydrate molecules in plant cells.
A human eats a
plant. Or a human
eats an animal
that ate a plant.
The chemical
energy stored in
the plant (or
animal) cells is
moved into the
cells of the
human's body. All
of the body
processes, like
digestion, pumping
blood, breathing,
are powered by
cells converting
the stored
chemical energy
into work and
heat, in a process
called respiration. Respiration takes
place in every cell in your body.
Introduction to Energy Changes ENERGY INDEX
Or The Changes that Make Things
ENERGY HOME PAGE
Change
THE MYSTERIOUS EVERYTHING
Energy is that "certain something"
ENERGY CHANGES IN
inside stuff (or matter to be more
precise) that makes everything happen. FLEAS AND CATAPULTS
When something or somebody moves or CONVERTING SUNLIGHT TO
jumps or falls or explodes or breathes or CHEMICAL ENERGY
thinks or dances or does anything, it's
HOW TO GET HOTTER
because energy is being transformed.
ENERGY FLOWS IN NATURE
Energy is being transformed or
changed from one type of energy to
ENERGY PYRAMID
another, or, in the case of heat flow,
HOW MANY FORMS OF
ENERGY?
from one place to another place.
FIRST LAW OF THERMO
SECOND LAW OF THERMO
There are
some things
about the way
energy always
behaves that
everybody (yes
everybody)
ought to know
about. This is the
section that will
introduce you to
the basics of
energy behavior.
You will discover
here that you are
very interested in
energy.
"This is good stuff," you will say to
yourself over and over, as you read
through these pages.
"I never
THE DEFINITION OF ENERGY
POWER & ENERGY
ENERGY IN THE WIND
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Inside the
muscle cells of the
human (or any
animal), the
chemical energy
is transformed
(changed) into
mechanical work
and heat. The
muscle contracts,
the legs push, and
the body leaps into
the air. Some of the
chemical energy
has now been
changed into the
kenetic energy of
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SUPER BUGS - PART 1
DR G'S WHALE PAGES
WHO WE ARE
DROP US A LINE
knew how
much I loved thermodynamics," you will
add as a happy afterthought.
We start with the stories of a dancin'
fool, a cd player, a locomotive, and
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We make mistakes.
We're always grateful when you
point them out.
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comments.
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Some Things You Should Know
About Energy:
1) For anything to happen there has
to be a transfer or change or
conversion of Energy.
- A transfer from one type of energy
to another type - like from chemical to
mechanical, or potential to kinetic.
Whole Lot of Changes
Goin' On and On and
On...
- Or a transfer of energy from one
place or area to another place or area
(an engineer would say from one
system to another system).
Chemical energy that was
"waiting around", doing nothing
much but "sitting" in the battery
being potential, suddenly
starts turning into electrical
energy. The new electrical
energy, formerly known as chemical, zips through some wires to
the electric motor that spins the disc. Now the energy that used
to be electrical has become the mechanical energy of the
spinning disc.
- Energy always
moves from a "higher
concentration" of
energy to a "lower
concentration" of
energy. (What the
hec does that mean?
We'll tell you in the
next installment).
2) There are two ways that energy
can be transferred - by work or by
heat flow.
In this section we are talking about
heat flow. Work will come later. (But
guess what! Down at the itsy-bitsy
micro level of molecules and atoms,
it's all really work! Really! It's all just
work! Heat flow is sort of an illusion. It
is the average effects of billions and
billions of atoms and molecules!)
3) Energy never appears from
nowhere or disappears into
nothingness. This reality is called the
First Law of Thermodynamics. Text
books often say it this way, "Energy is
neither created nor destroyed", or
"Energy is Conserved". (Those kinds
of definitions usually only make sense
to you if you already understand it.
So, if this is new to you, keep reading
for some easy to follow examples).
FURTHER NOTE: What about the
2nd Law of Thermodynamics, you
ask? Aren't I going to talk about that?
Yup. But not here. Well, we'll mention
it here and there a little, like in Item 1)
THERE HAS TO BE AN ENERGY
CHANGE TO MAKE THINGS HAPPEN!
Put a cd in your portable
player, put on the headphones
and flip the switch.
An electrical signal from sensors that "read" the spinning disc,
travels through a wire to the little speakers in the headphones. In
the headphones, the electrical energy that carried the signal,
now becomes sound energy (sound waves).
Where the Voices Inside Your Head Come From
Inside your head, sound energy in your ears is changed into
electrical and chemical signals that travel to a part of your brain
where those signals are turned into a sensation we call music.
Your brain sends electrical signals to muscles in your legs,
arms, face, and other places. Inside the muscle cells chemical
energy is stored in glucose
molecules (see Introduction to
Photosynthesis). The signals
from your brain tell your
muscles to contract. The
muscles convert the stored
chemical energy into
mechanical work, and you start
to move. (The process in plant
and animal cells that converts
glucose into work and heat is
called respiration). The energy
in the glucose came from a
plant or animal you ate. By
now, you should know from
where the plant got the energy.
You use a bunch of face muscles to smile. You move arm and
leg muscles in a coordinated manner (some people move in a
more coordinated manner than others). You strut and gyrate to
the music. Some people call this dancing. You're busy thinking
how cool you are while billions of cells in your body are busy
coverting chemical energy into work and heat.
above - the stuff on higher to lower
concentrations of energy is part of it.
The diesel powered locomotives rumble
and roar and a mile long train pulls out of
Denver. Thousands of tons of coal in more
than 100 coal cars is on its way to San
Antonio. Inside the coal are millions of BTU's
of stored chemical energy waiting quietly
for the chance to be converted into heat and
electrical energy at a power plant in Texas.
We take such human engineering
wonders for granted nowadays. It is
interesting to consider that the locomotives
are powered by stored solar energy, just
like the jumping humans above, and leaping
monkeys below. Just to keep you thinking
about such things, let's consider some of the
energy changes necessary to power a
locomotive.
A summary below, more detail in coming
pages.
Once again (and again and again and
again) it starts with that great fusion
furnace in the sky we call the sun. But in
this case it started a much longer time ago.
Just as described above, some of the solar
energy that landed on green plants was
converted into plant material and
carbohydrates.
This time, however, the plants weren't
eaten. This time they died, got buried, and
spent a good long while deep under the
earth being slowly turned into petroleum.
The crude oil that is
pumped out of the
ground is taken to an oil
refinery where it is
turned into all kinds of
hydrocarbon fuels like
gasoline, kerosene, jet
fuel, diesel fuel, and
more.
Now the energy changes in the engine
can start.
In the fuel tank the diesel fuel is stored
chemical energy waiting to happen.
Sometimes people call energy waiting to
happen potential energy.
You start to sing off key and too loudly because of the
headphones. Singing requires using the diaphram muscles
below your stomach to force air through the larnyx in your neck.
Once again chemical energy in the muscles is changed into
mechanical energy (and heat). Then the mechanical energy in
the contracting muscles is changed into mechanical pressure
and flow energy (kinetic) of the air being pushed out of your
lungs.
The larnyx changes the pressure and flow energy into sound
energy which travels as sound waves through the air and bothers
many of the easily annoyed people within earshot who don't
seem to appreciate your awesome talent. The sound waves in
their ears are also changed into electrical signals inside their
brains, but somehow they aren't as happy about it as you are. So
they don't use muscle cells to smile.
Epilogue to the CD-Dancer Story:
The First Law of Thermodynamics tells us that all of the
previously potential energy that came out of the battery and out
of the dancer's muscle cells doesn't go away to the mysterious
dimension of nothingness. It has to still be around somewhere.
Where is that somewhere? It all ends up as a slight increase in
the energy of air molecules.
Yes, it actually heats up the air a little bit. A little bit warmed
the battery, then flowed into the air. A little bit warmed the wires,
then flowed into the air. The spinning cd and motor did work on
some air molecules, causing them to zip around faster and
transfer their newly increased kinetic energy to still more air
molecules. The cells in your body gave off heat which flowed out
of your body into the air. Your dancing limbs also pushed billions
of air molecules out of the way. All of that heat and motion was
eventually transferred to the air, slightly increasing the energy of
billions of air molecules. After that it was radiated out into space
where it will help to warm up the universe an itsy-bitsy, teensyweensy (yellow polka-dotted) little bit.
That's really
what
happens. Energy
comes from the
sun, gets used
awhile, then gets
sent back out into
space. At the end
of its usefullness it
is what mechanical
engineers often
call low-grade
energy. When energy becomes low-grade it is no longer in a
form that is very useful to life (except maybe to help keep things
a little warmer). Having worn out its welcome, the hapless
energy radiates back out to the cold heat sink of outer
space. Luckily for us a new fresh dose of "high-grade" energy
from the sun radiates into the earth everyday.
Squirt diesel fuel into
a diesel engine cylinder
and suddenly the fuel is
burning so fast and so
hot we call it an
explosion. The potential
chemical energy that
was so quietly waiting in
the diesel fuel is turned
very quickly into heat.
The heated air and
combustion products in
the cylinder expand, the
piston is pushed down by the expanding air
pressure, the crankshaft turns, and
mechanical work is done. Chemical energy
was transformed into mechanical work. Ta
Da!
On a locomotive the diesel engine
crankshaft turns an alternator which
converts mechanical energy into electrical
energy. The electrical energy goes to giant
traction motors which convert the electrical
energy back into the rotating mechanical
torque that
turns the
wheels.
The turning
wheels push
the locomotive
forward. Now
the mechanical
energy
becomes the kinetic energy of motion of the
whole coal train. Don't get in front of it,
because it will require a lot of brake friction
turned into heat to stop this behemoth.
As explained elsewhere, all of this
energy eventually becomes low grade
energy from friction and from heat rejected
by the engine. This raises the surrounding
air temperature a little bit. Eventually the
energy is radiated back out into space. If it
didn't the earth would keep getting warmer
and warmer, and we would all find things
pretty uncomfortable.
(see the 2nd Law of Thermo Page)
In one liter of diesel fuel there are
approximately 39,887 KJ (37,807 Btu) of
potential chemical energy waiting to be
turned into heat. If all this energy could
be turned into work (which it can't) it
would be enough energy to lift a 1000 kg
weight 4070 meters (13,056 feet) above
the earth.
The best
locomotive engines
can turn only about
44% of the fuel they
burn into useful
mechanical work.
Another 33%, or so,
goes out the stack as
very hot exhaust gas.
The remaining 23%
goes mostly into the
cooling water and engine oil. All of the fuel
The Numero Uno Law of Thermodynamics says that, over
a certain period of time, the energy that is radiated back into
space plus the energy that stays behind on earth, has to exactly
equal the energy that comes in from the sun. If the energy
coming into the earth from the sun does not equal the energy
radiated back out into space, then the earth's average
temperature will change over time. If more energy comes in
than goes out, the earth's average temperature would start to go
up, and would keep warming up until the energy in and out is
again balanced. If more energy goes out than comes in, then the
earth's average temperature will get cooler.
This basic law of thermodynamics is why many scientists are
worried about the "green house effect". They are concerned that
increasing CO2 and other green house gasses will trap in more
energy over time and raise the average temperature of the earth.
Many scientists (but not all - we have to be fair) believe this is
already happening.
One More Time
"There Has to be a Change or Transfer of Energy"
We keep saying it. Nothing can happen in this wondrous
world without energy. Energy is that certain something inside
"stuff" that makes things happen.
But it isn't just energy. Energy
can sit around doing nothing for
a long time, like in a battery or a
tank of diesel fuel. Nothing will
happen until that "waiting"
potential energy gets changed
into another form of energy.
It's energy moving from one
place to another place, or
energy being changed from one
type of energy into another type
of energy, that makes things
happen.
A flashlight converts the
chemical energy stored in batteries
into light and heat. Most of the
energy is converted to heat. Only a
small percentage of the original
energy in the battery is converted
into light energy.
Is There A Definition?
This "energy-changing-making-things-happen" concept is
often not made quite clear enough in books and websites.
Thermodynamics is not so much the study of energy, as it is
the study of energy being changed. Energy that is not
"happening" is only a concept of what might be. Potential
energy for example is really just a mathmatical concept
describing something that can happen.
Think I'm being vague and evasive about energy? Listen to
what Richard Feynman, one of the best known physicists of the
twentieth century said, "It is important to realize that in physics
today, we have no knowledge of what energy is. We do not
energy, even the part that's turned into
useful work, eventually ends up heating
the air, then radiating out into space.
Isn't Energy the Ability to do Work?
Yes.
You will learn from text books and
other sources that the definition of energy
is "the ability to do work". That is the
standard definition. But we think the
definition we are using, "that certain
something inside stuff with the ability to
make things happen", is more helpful as
an introduction to the concept of energy.
For anything to happen work has to be
done on something. Even in the case of
heat flow, which in classical
thermodynamics is not considered a work
process, work is being done on molecules
or atoms.
At some level work is always being
done when something happens. So we
really are saying the same thing.
have a picture that energy comes in little blobs of a definite
amount".
Here's another one from a guy named David Rose (MIT
engineering professor famous for his work in fusion, energy,
and nuclear engineering): "Energy is an abstract concept
invented by physical scientists in the nineteenth century to
describe quantitatively a wide variety of natural phenomena".
Now do you understand?
That's why in the Mysterious Everything page, I emphasize
that what scientists and engineers really do is study, describe,
and predict, how energy behaves when it is in transition.
So learning about energy is learning how it behaves, what it
does and what it does not. We can use our knowledge of how
energy behaves to build machines and power plants and to
better understand the processes of nature, but we can't really
tell you what the heck it is.
I like it that way. Science is full of mysteries and
unanswered questions. A person can be properly scientific and
skeptical and still have a sense of wonder. If you're a person
who has to have all the answers, then you probably won't like
science.
Scientists have to spend a lot of time wondering and asking
questions. Science still has many more questions than answers
- lots and lots to learn. Lots of stuff for good science
"detectives" to find out.
Contact Us
Thermodynamics is more than just a
fun-to-say word. It is also a field of science
and engineering. All this stuff about energy
conversions and heat and work is stuff that
you will study when you study
thermodyanamics.
But you can't truly be a thermodynamic
know-a-lot unless you know the following:
The word "thermo" comes from some
old time language and stands for heat or
energy (depending on who you talk to),
while "dynamics" stands for something like
movement or motion or change. So together
they sort of mean "energy-changes" or
"energy- movement".
It's energy changes we're interested in.
Energy wouldn't be very interesing if it
never changed. Nothing would be very
interesting because nothing would ever
happen.
In the next section we discuss the concept of heat flow more
thoroughly.
An understanding of heat and heat flow is necessary to fully
appreciate the fascinating ways animals and engineers control
the flow of heat. Some fascinating examples of such things will
be coming to these pages soon.
Don't forget the cute diagram below on energy conversions in
monkeys.