Transcript Energy - MHS Chemistry

ENERGY
energy !
All changes in a system - physical or chemical - are accompanied by a change in _________________.
Energy - What is it?
go to school, move, swim, walk to the
kitchen, play tennis, try, deal with Emmanisa,
“I don’t have enough energy to _________________________________________”
get out of bed, think, come to
Chemistry/Interp, live, eat
do something
to __________________________
Energy is associated with ________________________________________________
doing / action = CHANGE
Energy - defined as
the potential to do work
‘energy’ Greek for ‘work within’
ability to make happen
What’s Work ?
everything (effort), building a tree house or tire swing, pushing
first, examples of work : a carrot, pulling a banana, running in field hockey, cooking a
BIG meal, growing, living with siblings, shoveling snow, split
why is energy involved ? wood
work involves moving something against a force (pushes / pulls)
- you do work, or work is done, on an object to move
it against a force (the object gains energy)
- work is done by an object when it moves with a force (the object loses energy)
The Rock….
There are Four Forces
- gravity - “Rules the Cosmos”, Hecht
attractive force between ALL objects - scales with mass
- electromagnetic (e/m) between charged objects - governs chemistry and biology
attractive between oppositely charged objects
repulsive between like charged objects
+
+ +
includes:
the forces of
Chemistry
-
friction
cohesion
adhesion
chemical bonds
-
drag
tension
- fist and wall
collisions - teeth and hamburger
(contact forces)
- strong - holds parts together in the nucleus
protons, neutrons / quarks
- weak
- transforms one type of quark into another
associated with nuclear decay
-
- forces of nucleus
and nuclear decay
- effective over very
small distances <10-15m
Forces and Energy are properties of matter
Forces - exist between bodies - cannot have a force with ONE body
if one considers energy as
Energy - consequence of forces - then energy is a property of matter
energy is of a body, not an entity unto itself
- you cannot have a cup of energy,
anymore than you can have a cup of color
Energy is stored (in matter) as
position
potential energy (PE) – energy a body possesses due to its ______________
- implies another body (as position is defined relative to something else)
- if there are two bodies, they interact by one or more forces
- PE is the energy stored in the bodies due to the force between them
- the magnitude of the force changes as the relative position of the
bodies changes, so….. the PE depends on the distance between bodies
motion
kinetic energy (KE) – energy a body possesses due to its _______________
- larger mass, moving faster = higher KE
- can’t have motion without a push/pull OR
two or more bodies must interact via a force for one (or all)
of them to move
The Waterfall
The Dam
OPEN THE DAM!!
The Lake
The Turbine
The River
The Waterfall
The Dam
HIGH PE
water at the top of the lake has high PE
as it falls due to gravity
its PE turns into KE
the moving water can do work
on the turbine
The Lake
The Turbine
PE – the potential to do work
 work involves moving
 cannot “see” the expression of energy
until objects are in motion
PE
KE for work to be done
LOW PE
The River
Forms of Motion (Kinetic) Energy
kinetic -energy a body possesses due to its motion as a whole object
the whole body moves in a uniform (one) direction
OR
uniform motion of all the parts that make up the whole
thermal -energy a body possesses due to the motion of its parts
the parts = all parts down to the atomic/subatomic scale
the motion = random (all directions) motion
temperature
measure as the ______________
hot / cold
water and
dye….
Forms of Positional (Potential) Energy - Because there are different types of forces,
bodies can interact or move with or against these different forces.
Change occurs as a consequence of these different forces, so we see/experience
different manifestations of energy.
OR
There are different forms of potential energy depending on the different force involved.
FORCE
gravitational
chemical
nuclear
elastic
electrical
INTERACTING BODIES
Forms of Potential Energy
There are different forms of energy depending on the different force involved.
FORCE
INTERACTING BODIES
gravitational PE gravity
all bodies - scales with mass
stored in any body due to its gravitational interaction with another body
nuclear PE
nuclear particles (protons, neutrons, quarks)
strong / weak
stored in the nuclear particles
e/m
any protons (+) and electrons (-)
electrical PE
stored in an electron due to its position relative to other protons and electrons
elastic PE
e/m
protons (+) and electrons (-) of bonded atoms
stored in bonded atoms due to the compression/stretching of chemical bonds
chemical PE
e/m
protons (+) and electrons (-) of bonded atoms
stored in a bonded atom due to its e/m interaction with the other bonded atom
And Radiation – radiowaves, microwaves, infrared, visible, ultraviolet, X-ray, gamma ray
solar energy - primarily infrared (IR), visible, ultraviolet (UV) radiation
where is radiation ?
in space
( not in matter
)
 originates in matter – travels through space
 e/m in origin
radiation is produced as charged particles
move relative to each other
NOTE: the sun is HOT
- 3,000,000 C (core)
- 6,000 C (surface)
. BUT,
the thermal energy
does not reach the Earth
92.3×106 miles away.
We are warmed by the
infrared radiation
nice example
battery – electrical PE
hook up the battery – electrical PE to KE (electrons moving)
can do the “work” (light the bulb or whatever)
the electrons flowing in the wire move past other electrons/protons
generates radiation
It is practically impossible ( in practice, cannot do )
to calculate the total amount of energy a body possesses because
one would need to consider the interaction of that body with __________________
every other body
___________________________________________________________________
in the universe (interacting through one or more of the four forces)
However, there is a law about the total amount of energy in the universe:
Conservation of Energy
The Law of ______________________________________
that states _______________________________________________________
energy cannot be created or destroyed
_____________________________________________________________
OR the total amount of energy in the universe is constant
energy can be ________________________
transformed
transferred
energy can be _______________________
even though the total
by _____________________
work
energy cannot be calculated,
________________________
heat
the amount of energy
radiation
________________________
gained or lost by an
object can be
Examples of Transfer and Transformation of energy
Lifting a rock with your hand
you moved the rock
against / with ________________________________________________
gravity (between the Rock and Earth)
you did __________
on the rock
work
transfer of energy by __________
work
from _______
to ___________
you
the Rock
the rock gained / lost ____________________________________
gravitational PE
as a result of
_________________________________
your arm pushing
transformation
_________________________________
muscles contracting
_________________________________
food consumed next slide
energy stored in
available
to do…
(many steps / chemical changes)
food ……………………….……………. ADP + phosphate + ENERGY
chemical PE
energy stored in food as ____________________________
next slide
many steps
food
(mostly
carbohydrates)
glucose
+ oxygen
ATP + carbon dioxide
+ water
energy stored in
ATP
(hydrolysis)
ADP + phosphate + ENERGY
useful energy in food is stored in chemical bonds
back to previous slide
available
to do…
Examples of Transfer and Transformation of Energy
Transfer of Energy by Heat
When you heat something it gets _________________________________
hotter
So, heat / heating has something to do with Temperature and Hot and Cold
What happens when you put a hot object next to a cold object ?
____________________________________________________________
the
cold object gets hotter, and the hot object gets colder
____________________________________________________________
until
they are at the same temperature
HOT
COLD
How ?
Something that is HOT has relatively high thermal energy
the individual particles of the object are moving relatively FAST
Something that is COLD has relatively low thermal energy
the individual particles of the object are moving relatively SLOWLY
relatively high thermal energy
particles of the object are moving relatively FAST
HOT
COLD
relatively low thermal energy
particles of the object are moving relatively SLOWLY
HOT
COLD
HOT
COLD
at the interface, the “hot” and “cold” particles collide
faster goes slower (colder), slower goes faster (hotter)
the interface spreads throughout the bodies, until the particles
are moving at the same speed (at the same temperature)
HOT
COLD
HOT
COLD
at the interface, the “hot” and “cold” particles collide
faster goes slower (colder), slower goes faster (hotter)
the interface spreads throughout the bodies, until the particles
are moving at the same speed (at the same temperature)
HOT EDIU COLD
HOT MEDIUM
COLD
HOT MEDIUM COLD
Transfer of Energy by Heat
energy is transferred
(technically) Heat is not ____________________
it is a way that ______________________
a form of energy
(Hecht quote)
“Heat is thermal energy in transit,
and once transferred it is no longer called heat” [it is again thermal energy].
(Thermal) energy is transferred by heat between objects that are
_____________________________________
in contact
and, _________________________________
at different temperatures
Law of Conservation of Energy (and Matter) and our Energy Crisis
Law of Conservation of Energy
Over hundreds of years,
experiments have shown that there is no net gain or loss of energy in the universe
(as long as one accepts that matter is a form of energy).
So, how can we be in an “energy crisis” ?
How can we be running out of energy ? we can’t be
we are running out of energy in useful forms (or places)
(useful for some purpose)
So “consuming energy” means ______________________________________
transforming /transferring from
________________________________________________________________
useful forms to less useful (or not useful for the same purpose) forms
fossil fuels (matter)
What are we running out of with respect to the energy crisis? ________________
(mostly ~90%) burning it (transformed)
What is happening to this ? ________________________
Type of change ? ________________________
chemical (evidence? flame )
What are we running out of with respect to the energy crisis? _________________
petroleum (matter)
(mostly ~90%) burning it
What is happening to this ? ________________________
Type of change ? __________________________
chemical (evidence? flame )
(burning fossil fuels)
Fuel + O2
CO2
+
H2O
new substances form - bonds break / new bonds form
Chemical change: __________________________________________________________
in chemical bonds
With respect to a chemical change, useful energy is stored __________________________
(chemical PE)
so, as the fuel burns,
chemical PE of (Fuel + O2)
chemical PE of (CO2 + H2O)
BUT, the point of burning the fuel is not to produce CO2 and H2O.
thermal energy (and radiation)
The point is to “get the energy out” as ___________________________
where was the thermal energy and radiation to begin with ? ____________
in the fuel
(and O2)
as ? _____________________
chemical PE
some of the chemical PE of the fuel (and O2)
is transformed to thermal energy and radiation
The Waterfall
The Dam
Gravitational PE
HIGH Gravitational PE
high water
total
energy
total
energy
low water
GravPE (high water)
this amount of gravitational PE
is transformed to KE
(energy of the moving water)
The Turbine
LOW Gravitational PE
GravPE (low water) + KE (moving water)
if the falling water
if thehits
falling water hits
the surface of athe
pond/river
turbine
KE+PE (splash)
KE (sound)
thermal
electricity
Chemical PE (bond energy)
Burning Fuel
The Fire
HIGH Chemical PE
fuel (C2H6) + O2
total
energy
this amount of chemical PE
is transformed to thermal and radiation
total
energy
CO2 + H2O
ChemPE (fuel + O2)
LOW Chemical PE
ChemPE (CO2 + H2O) + thermal & radiation
The Energy “Crisis”
So “consuming energy” means _______________________________________
transforming /transferring from
________________________________________________________________
useful
forms to less useful (or not useful for the same purpose) forms
Transformation (consumption) of energy
chemical PE (fuel + O2)
chemical PE (CO2 + H2O) + radiation
& thermal energy
transferred
transformed
LCE – no gain / loss in energy….. so……
chemical PE (fuel + O2)
has to equal
chemical PE (CO2 + H2O) + radiation
& thermal energy
so, what’s the problem ?… no energy has been lost….
1.
low (not as useful)
2. Where does thermal energy go?
- out / everywhere
- escapes in to the universe – “lost” / not useful
To heat our buildings
the energy is
ultimately “lost”
as thermal energy
escaping into
the universe
transfer of thermal
energy by heat
cold HOT
air
(some of)
chem PE (fuel)
thermal energy (flame)
transform
WARM
COLD
transfer of thermal
energy by heat
To produce electricity
transfer of kinetic
energy by work
cold
transfer of thermal
HOT energy by heat
(some of)
chem PE (fuel)
thermal energy (flame)
transform
electricity
light (radiation)
transform + thermal energy
kinetic energy
electricity
transform
To produce electricity
electricity
light (radiation)
transform + thermal energy
HOT
COLD
transfer by heat
the energy is
ultimately “lost”
as thermal energy
escaping into
the universe
transfer
ansfer
kinetic energy
electricity
transform
thermal energy (flame)
form
Transportation
transform
thermal
kinetic
hot gases expand
- can only expand “up”
moves forward
transfer of kinetic
energy by work
cold
HOT
transfer of thermal
energy by heat
(some of)
chem PE (fuel)
(KE)
KE
thermal energy
transform
thermal energy (flame)
transform
transform
the energy is
ultimately “lost”
as thermal energy
escaping into
the universe
work
Useful Energy can do _____________
force
move something with respect to a __________
a direction
implies _______________
(outward/inward is a direction)
to move something (THING 1)
move towards Thing1
something else (THING 2) must _________________
____________________
and HIT Thing1
Useful Energy can do work
= move some object in some direction
Thermal energy
random motion of particles within a mass (object)
cannot do __________________
(no net direction of motion)
work
UNLESS it is trapped in an expandable/contractable container
(the hot mass)
example: in a piston, trapped hot gases expand
to push a piston up
in a power plant, trapped hot gases expand
thermal
kinetic
to turn a turbine
untrapped, thermal energy escapes into the universe
and is no longer useful to do work
thermal energy =
degraded energy
The Waterfall
The Dam
The Lake
The Turbine
The River
The Waterfall
The Dam
HIGH PE
The Lake
The Turbine
LOW PE
The River