Transcript No Slide Title

1
An attempt to take ideas about Energy and Conservation from
several disciplines and form an integrated organization.
2
Statements about energy from various sources:
1. There are many forms of energy: wind, water, sun, potential,
chemical, electrical, nuclear, light, motion, heat, mechanical,
internal, external, atomic, nuclear, molecular, gravitational, bond energy,
bonding energy, sound energy etc.
Energy can change from one form to another.
Energy is Conserved
2. Potential Energy can be stored in an atom or nucleus or molecule
or by gravity or in a battery”
3. Work: Force times Distance= KE= 1/2 mv2
PE= mgh
4. In an exothermic reaction heat is given off by a chemical reaction. The energy comes
from substances involved.
5. Electricity often turns into heat
6. A windmill can turn wind energy into electrical energy
7. Nuclear energy is very large and comes from the nucleus! Both fission and fusion
produce energy.
8. Potential energy is in a form you often cannot see.
3
Where does the confusion about energy come from?
4
1. Why is it “work” to push on a wall? We get tired! Books say no work is done!
2. Do these topics have any conceptual similarities as we teach them. Biology (sun energy,
cell energy, chemical energy, potential energy), Physics (mechanics:gravitational potential energy
and kinetic energy, frictional heat energy), thermodynamics: heat transfer, nuclear and electrical
energy), Chemistry (thermochemistry, bond energy, nuclear energy, heat of reaction, heat of fusion
and evaporation and in all areas The Law of Conservation of Energy
3. How do you describe how energy is stored in molecules and bonds and the nucleus?
4. In an exothermic reaction where exactly does the heat come from?
At the atomic level what is the same for all exothermic reactions?
5. What is the connection between mass and energy?
6. How is electrical energy related to the equations of Mechanics in Physics?
7. How are all the different Forms of Energy..mentioned in most texts …..related? Are there really
so many different forms of energy?
8. How is Work done actually related to PE, KE, heat, electricity ?
9. How is Binding Energy related to energy given off in nuclear reactions? Is Binding Energy a form
of energy?
10. What do all the forms of Potential Energy have in common?
5
…………………………………Some confusing definitions…………………………..
Definition: Energy is the capacity of a physical system to perform work. Energy exists in several forms such as heat, kinetic or
mechanical energy, light, potential energy, electrical, or other forms.
Energy Definition: Energy may be defined as the ability to do work. It is a scalar physical quantity. Although energy is
conserved, there are many different types of energy, such as kinetic energy, potential energy, light, sound, and nuclear energy
… a form of power such as , electricity, heat or light
that is used for moving things around…work.
…the power that is present in all physical things and that can be changed into something such as heat, movement or light.
Electrical energy is the movement of electrons. That is kinetic energy. The voltage in an electrical circuit is the potential
energy that can start electrons moving. Electrical forces cause the movement to occur.
Chemical energy is potential energy until the chemical reaction puts atoms and molecules in motion. Heat energy (KE) is
often the result of a chemical reaction.
Confusion also comes from using “h” instead of h for example in “mgh” and Vlost instead of V in V=IR and energy =
VIt etc etc
The following are
examples using
consistent concepts
of KE and PE
throughout science
6
Definitions that prove consistent throughout the curriculum:
1. Work is the Transfer of Energy from one form or condition to another.
Mass=Energy is always Conserved in all interactions
2. There are 3 forms of energy: kinetic, potential and electromagnetic.
(Mass is converted into Energy via E= Δ mC2)
3. Kinetic energy may assume the form of Macroscopic 1/2 MV2 or
Microscopic Heat. (Heat in or out can be calculated)
4. Potential energy is associated with the relative positions between
bodies. Most common: Since all molecules and atoms and opposite
charged ions attract each other …Potential Energy goes UP
when attracting bodies move away from each other and
goes down when they approach…at least until they get to their
“bond distance” in which case repulsion becomes greater than attraction.
Ultimately all losses PE involve mass being converted into energy.
5. Electromagnetic energy refers to any of the electromagnetic spectrum.
7
8
Examples of sources of potential energy in systems
1. Gravitational: Masses attract the earth…when moved further away PE goes up.
2. Electrostatic
A. Electrical:
When electrons are moved from protons PE goes up; when electrons
are moved closer together PE goes up. …as in charging a capacitor etc.
B. Chemical:
Anytime PE goes up: Sum of attracting bodies get further apart and
repelling bodies get closer together. It often is difficult to see all of this
but if you analyze simple systems you can see it at work.
4. Nuclear: In any exothermic nuclear reaction…be it fusion or fission it can be shown
that potential energy goes down because attracting bodies are getting
closer…the nuclear force of attraction is much larger than the electrostatic
forces of repulsion.
Potential energy can be shown in graphical form for ALL
changes….not just chemical reactions.
9
Kinetic
Potential
A and B
C
Electromagnetic
D
10
Macroscopic KE
A 1/2 M V2
C
D
E=MC2
For now EM is
left out of the scheme.
B Heat
Microscopic KE
Within each category
energy can go from one
body to another
Conversions within a category
1. Potential Energy:
a. Chemical PE -----Electrical PE: Battery charging capacitor
b. Gravitational PE-----Spring PE: A mass set atop a spring compresses it.
c. Chemical PE -----Gravitational PE: Lift a box
2. Kinetic Energy
a. Microscopic KE: Heat flows from hot to cold
b. Macroscopic KE: Two billiard balls collide.
3. Electromagnetic Energy
a. Fluorescence: UV changed to Visible light
Kinetic
A
1/2 M V2
Potential
Electromagnetic
C
E=MC2
B Heat
Within each category
energy can go from one
body to another
1. Expanding gases cool: B to C
Compress gases: C to B
2. Water evaporates and cools: B to C E=MC2
Water condenses: C to B
3. Wax freezes on your finger: C to B
Wax melts: B to C
4. Car brakes to a stop: A to B
Engine accelerates car: B to A
5. Exothermic chem reaction: C to B
Endothermic chem reaction: B to C
6. Bullet shot from gun: C to B & A
Car bounces down on springs: A to C
7. Car coasts up a hill: A to C
Car coasts down a hill: C to A
8. Driver brakes down a hill: C to A & B Car brakes going up a hill: A to B & C
9. Pendulum: C to A and A to C
Eventually: all ends up as B
10. Drop a book on the table: C to A to B Pour hot water into cold: B to B
11. Lift a rock:Cbody to Cgravity
Push on the wall: C to B
12. Pool balls collide: Aball 1 to Aball 2
A mass compresses a spring: Cgravity to Cspring
13. Battery lights light bulb: C to B etc Electric motor: Celectrical to A and B
11
The Law of Conservation of Energy
Energy is never destroyed; it just changes
forms. (JUST CONSIDER POTENTIAL AND KINETIC )
PE
Example:
Boils down to:
+
KE
5 + 5 = 10
6 + 4 = 10
8 + 2 = 10
= CONSTANT
If PE gets bigger then KE gets
smaller
KE + PE =
0
12
A good definition below
The bonds between atoms are the source of all chemical or covalent type have relatively
low potential chemical energy, as it requires a large amount of outside energy simply to
break the bonds. Weaker bonds, like those of the van der Waal type, have more potential
chemical energy, as they require relatively little energy to break.
Energy is released when these bonds form between atoms, and the energy in chemical
reactions is not created or destroyed. This means that chemical reactions may be analyzed
like mathematical equations. Since a strong bond requires a large amount of energy to
break, this must mean that when that same bond forms, much energy is released. By the
same logic, when a weak bond forms, relatively little energy is released .
13
14
Hydrogen gas + chlorine gas ==== hydrogen chloride gas
74
+
H+H
Exo
PE
199
Cl + Cl
>
273 > 254
2 ( 127 ) bond distances pm
H + H + Cl + Cl
Endo
H2 ……………………………………………… H2
Exo
Endo
Cl2
…………………………….. Cl2
Exo
Endo
PE average
Exo
Coordinate
2H = H2 + heat
2Cl = Cl2 + heat
2H + 2Cl = 2HCl + heat
H2 + Cl2 = 2HCl + heat
The Net reaction is Exothermic because the bond distances between hydrogen and
chlorine are smaller than between hydrogen-hydrogen or chlorine-chlorine…PE is down.
15
16
PE + KE = 0
A Simple Chemical Reaction
C(g) + 02 (g)
------ CO2(g) + heat
121 > 113
PE +
C
+
PE
KE
O
KE
O
O
O
C+O+O
PE
+
Atoms are closer together
O2 + C
…………………….
Coordinate
CO2
Combustion of Methane
1 CH4 + 2 O2
+2632 kj/mole ch4
17
2 H2O + CO2
-3338 kj/mole methane
916 > 848
992 kj/mole O2
2 O2
120 pm
1486 kj/mole
CO2
1640 kj/mole
Ch4
109 pm bond length
116 pm
1852 kj/mole methane
2 H2O
96 pm
19
20
Thermochemistry
21
For example: Suppose 35ml of 80C water is mixed with 19ml of 24C water.
What is the resulting temperature?
(60 C)
Heat energy is transferred from hot object to a cooler one.
COLD
HOT
Kinetic energy falls
Energy Conserved
Kinetic energy rises
1. Hot water is mixed with cold water H = MC  T= KE change
Δ Hhot water
+ Δ Hcold water
[ (35g)(1cal/gC)(T2 - 80C)]
+
=
ZERO
[(19g)(lcal/gC)(T2 - 24C)]
T2 = 60 C
= 0
22
Determining the Specific Heat of Iron2
Heat a 1.0 kg mass in water to about 80 c. Place 200 ml tap water in a styrafoam cup, measure temp. and insert mass.
T1 Water = 22.2C
heat
Kg
200.0 ml water
T1 iron = 81.2 C
Measure T2:
0 = heat lost by Fe + heat gained by water
0
= mc Δ t iron
+
mc Δ t water
0 = (1000g) (CFe) (T2-81.2C) + (200g) (1cal/gC) (T2-22.2C)
Insert the final temperature and solve for CFe
Notice that in the following problems
that delta T can always be interpreted
as T2 – T1 and no confusion of what to do.
23
24
Some examples
1. Going from solid oxygen to nucleons.
Δ PE + Δ KE = 0
up
6
Nucleons
5
Ion
s
down
4
PE
Atom
s
3
2
1
solid
Δ PE + Δ KE = 0
Gas
down
up
Liquid
1-2. O2(s) + energy --- O2(L)
2-3 . O2(L) + energy ----- O2( g )
4-5 O(atom) + Energy ----- O(ion) + 8 electrons
5-6 O(ion) +
3-4. O2(g) + energy ---- 2 O(g)
Energy
---- 8 protons + 8 neutrons
25
Ice…to....nucleons thru heating
Ionize O
atoms
Heat O
atoms
Vaporize
Water
Heat Ice
Melt Ice
Heat
Vapor
Nucleons
Heat
ionz
Decompose
O
water
*
O
nuceons
O
Heat
Water
*
O
O
ions
Total
Energy
*
O
*
atoms
gas
O
*
liquid
solid
*= phase change
KE
PE
26
Demonstration
Have a student insert one finger into 60F liquid wax and another
into 60F water. Essentially both will feel the same.
Now remove both fingers: the wax gets hotter as it freezes and the
water gets cooler as it evaporates.
Water
Gas
PE
Liquid
Heat Absorbed
Wax
Liquid
PE
solid
Heat given off
27
Ice in Water
ICE
heat
0C
Water
PE ice
KE water
Heat from the water is used to (1) melt the ice and (2) warm
the resulting ice water.
18
Burn methanol with oxygen to make carbon dioxide and water + heat
108 pm
2
96 pm
95 pm
143 pm
3
=
4
2
113 pm
121 pm
1850 total to 1672 total = atoms closer together and PE down
0 = KE
+
PE
28
Solid Hot Wax
Liquid Hot Wax
Water
Thermochemistry
20g of wax at 80C in mixed with 50ml of water at 25C. What is the final temp?
Fd
= Δ PE
0
=
(
+ Δ KE (macroscopic) + Heat
-)
+
0 = (Mass x H fusion wax) +
0
0=
-
- 400)
1810
+
+
52 T2
2T2
+(
-)+(+)
[(Mwax x Cwax T) + (M x Cwater T)]
0= [(20g)( - 20cal/g)] +
[(20g)( 0.1cal/gC)(T2
Heat of fusion is (-) PE goes down
cools
0 = (
+
+ ( - 160 ) +
- 80C)]
( + 50T2)
+ [(50g)(1cal/gC)(T2 - 25C)]
heats
+ (-
1250 )
T2 = 35 C no confusion about t
29
Dissolving
Some compounds are exothermic when dissolved,
some are endothermic when dissolved and some
don’t seem to affect water temperature when dissolved
Dissolving of Ammonium Chloride Endothermic
30
+1
NH4 +1 (g) + Cl-1 (g)
-1
PE
PE
DISSOCIATION
(lattice energy)
HYDRATION
- 307 kj/mole
NH4 +1 (aq) + Cl-1 (aq)
+ 705 kj/mole
0
+1
NH4Cl (s)
-1
H = +18 KJ/MOLE
+
Note: H20 = 0 = -
0
+1
- 381 kj/mole
0
0
0
0
1-
0
0
Dissolving of Sodium Hydroxide
exothermic
Na +1 (g) + OH -1 (g)
PE
DISSOCIATION
31
-1
+1
PE
HYDRATION
NaOH (S)
+1
-1
Na+1 (aq) + OH-1 (aq)
H = - 45 kj/mol
o
o +1 o
o
o o
o -1 o
o o o o
32
Dissolving of Sodium Chloride very slightly exothermic
-1
+1
Na+1 (g) + Cl-1 (g)
PE
+787 kj/mol
DISSOCIATION
+1
NaCl (s)
-1
4
0
6
=
- (406 +363) = -788 kj/mol
HYDRATION
o
o
+1
o
o
o
-1
o
o
o o
o o
Na+1 (aq) + Cl-1 (aq)
Delta H = -1 kj/mol
33
Thermochemistry
Example: Add 5.0 g of ice at 0C to 100ml of water at 25C. What is the final temp?
Δ H = mC(specific heat) Δ T = Δ KE Δ H = m (Hf) ….heat of fusion = Δ PE
H25C
Δ Hice =(5.0g) (+80 cal/g)
water=(100g)(1cal/gC)(T2-25C)
Hice water=(5.0g)(1cal/gC)(T2-0C)
warm water cools
(Use +80 when PE rises and -80 when PE falls;
when a substance freezes the attracting particles
get closer together and PE goes down. This also
happens with water but because of hydrogen
bonding its less obvious to see….ice floats)
cool water heats
ice melts
Δ H total =(100g)(1cal/gC)(T2-25C) + 5.0g)(1cal/gC)(T2-0C)+ 5.0g) (+80 cal/g) = 0
KE goes down
Δ KE
+ Δ KE
(-)
+
KE goes up
+ Δ PE
(+)
Conservation of Energy
100T2 - 2500 + 5T2 - 0 + 400 = 0
+
PE goes up = 0
=0
(+)
Final Temp = 20C
Exothermic Reactions
34
A. 2.0g (0.050mol) of Na0H are put into 300ml of water at 22C and the temperature
rises 2.5C. What happened to the Potential energy of the Na0H?
Fd
= Δ PE
+ Δ KE (macroscopic)
= Δ PE
0= Δ PE + mC Δ T
0= Δ PE +
0
+
+
Heat
0
+
heat
(300g)(1cal/gC)(+2.5C)
chemical PE is lost and KE transferred to the water
Δ PE= -750 calories
The reaction is EXOTHERMIC!
B. 0.10mol of Ammonium Chloride dissolves in 250ml of water and the temp
drops from 24C to 21C. What is the  H of the reaction?
Fd
0
= Δ PE
= Δ PE
+
+
Δ KE (macroscopic)
0
+
+
Heat
mC Δ T
0= Δ PE + (5g)(1cal/gC)(21C-24C) KE is lost by the water and converted to PE
in the chemical system
0= Δ PE + (-15cal) Δ H = + 15cal or
+ 150cal/mol
ENDOTHERMIC!
35
Line Spectra : Δ PE + Δ Electromagnetic energy = 0
down
36
up
Energy levels in a hydrogen atom
0= Δ PE
+ Δ EM energy
“ As the attracting electron gets further from the nucleus the PE goes up”
N=4
IR
N=3
PE
PE
Visible light
PE
N=2
UV
N=1
0
PE
Ionization
37
Calcium 2, 8, 2
Ionization Level
1st
e
Ionization energy increases as electrons
closer to the nucleus are reached.
Rise in PE corresponds to more work
needed to be done to remove it.
1st Electron …Outermost
2nd Electron
3rd Electron
38
External Work Done on a Body
changes to
Kinetic Energy (macroscopic)
Kinetic Energy (microscopic)
Potential Energy
Mechanics
39
1. Work in mechanics (F d) is an usually is an instance where external energy
is transferred to a system.
2. Most texts show equations like: Fd = KE or Fd=PE
Fd=mgh
Fd=1/2mv2
This leads to an incomplete understanding of just what is going on.
The equations are really:
External work Fd= mg Δ h
and
Fd= Δ KE = 1/2 mv22 -1/2 mv12
3. A system that consistently works in mechanics is:
Work
= change in PE +
generated
Fd
= Δ PE
FΔd
= mg Δ h
FΔd
= mg Δ h
change in KE
+
heat
+ Δ KE (macroscopic) + Heat
+
(1/2 mv22 -1/2 mv12)
+
+ (1/2 mv22 -1/2 mv12) +
Which is the same as 0 = F d +
heat
Ffrictiond
Δ PE + Δ KE +
heat
Mechanics
40
Suppose a 2.0 kg block at rest slides down a frictionless ramp 25 cm high
and out on a horizontal surface upon which there was a friction force of 4.0N.
Where does the block stop?
No external work is done.
FΔd
=
0
=
mg Δ h
(
-)
+
+
(1/2 mv22 - 1/2 mv12)
(0)
-
(0)
+
+
Ffrictiond
(+ )
Suppose a 2.0 kg block at rest slides down a frictionless ramp 25 cm high
and out on a horizontal surface upon which there was a friction force of
4.0N.
Where does the block stop?
No external work is done.
Zero = 0 = [(2.0kg)(9.8N/kg)(-0.25m)] + [0 - 0]
d=+1.23m
+ [4.0N)(d)]
41
Mechanics
Suppose YOU lifted a 3.0kg block vertically upward 9.0 meters and let it slide down
an incline upon which the constant force of friction was 15N. What would be the
speed of the block after it had slid a distance of 4.0 meters 15m down the incline and
dropped a vertical distance of 3.0 meters? Only consider the starting and ending
points involved
FΔd
(+)
=
mg Δ h
(-)
+
(3.0)(9.8)(+9.0) = (3.0)(9.8)(-3.0) +
+265 J
= - 88.2J
V2 = 14 m/s
+
(1/2 mv22 - 1/2 mv12)
zero
+
( 1/2 (3.0)( v22 ) - ( 0 )
1.5 V22
+
+60J
Ffrictiond
(+)
+ (15)(4.0)
42
The curious example of taking energy from something
by pushing on it.
KE1 = 40 J Applied Force
4N
Frictionless
Motion
10 m
F•D = Δ PE + Δ KE + heat
From the dot product we get negative work…which \
means we are taking energy out instead of putting it in.
0 = - F•D + Δ PE + Δ KE + heat
0 = -[-FD] + 0 + Δ KE + 0
0= +(4)(10) + KE2 - KE1
0= +40 J + 0 - 40J
40 J of some form of energy must be created from the
lost KE; we know we did “work” …in fact as much
work is done stopping it as was done getting it going.
43
The amount of work we did took energy from the
block and therefore that amount of energy must be
vented via heat from our bodies. This term does not
appear in the equation for the same reason as when
we push on a wall and get tired we are actually
working on the air….its gaining energy…but this
equation can’t be used to “measure” the energy
gained by the air. We can calculate the energy gained
by the air in the above case with reason.
If you did 40 J of work lifting a rock you would do
40 J of work setting it gently back down. In setting it
down the rock loses 40 J of PE and you lose 40 J of
heat….explaining your sense of getting tired.
44
Potential Energy
changes to
KE (macroscopic)
KE (microscopic)
Other form of PE
45
Δ
Electricity: V=IR and EL = IR
Ohm’s Law
PE
V1Q
Δ VQ= Δ VIt
PE
Electric Field
ELQ=VIt=  PE
Q
V2
KE or Heat
-
+
R
L=length of resistance: HEAT formed
46
Suppose you touch a charged van der graaf at 50,000 volts
And 2 x 10 -6 coulomb of charge flows thru your body.
How many joules of heat is generated?
V x q = 50,000 j/c x 2 x 10 -6 coul = 1 x 10 -1 j
same as a kg falling 1 cm
Electrical PE changes to electron KE which changes into heat.
 PE electrical = PE gravitational = same amt of heat formedl
PE + KE electrons = 0
KE electrons + KE atoms = 0
47
Electricity
A 1.5v battery delivers 0.30amps to a toy car for 5.0 s and the 1.0kg car goes
from rest to 2.0 m/s in that time. How much energy is “wasted” as heat?
= Δ PE
Fd
+ Δ KE (macroscopic)
+
Heat
Change of electrical potential energy is: Δ VIt or( Power x time)
Δ V is really Vlost in all equations using ohm’s law: V=IR
FΔd
= Δ VIt
zero
= Vlost I t
0
0
+
+
= (-1.5)(2.0)(5.0) +
= -15J
+
battery lost 15J
(1/2 mv22 - 1/2 mv12)
1/2mV22 - 0
+
+
Ffrictiond
heat
(0.5)(1.0)(3.0)2 - 0
+ heat
+4.5J
+ heat
car gained 4.5J
gained heat 10.5J
48
The Role of Mass
“The Rest Mass particles have is simply the work done in
separating them against their mutual attraction after they are
created” Richard Feynman
This implies that when particles that attract each other are
moved closer and PE goes down…energy must be given off
and MASS MUST BE LOST.
In the case of burning a mol of carbon to carbon dioxide the
amount of KE (= to loss of PE) is equivalent to 5x10-9g.
In normal chemical reactions this mass loss is not measurable.
49
Potential Energy
changes to
KE (microscopic)
50
Binding Energy: The energy
required to take apart attracting
bodies…Texts: energy “stored”
in the atom.
In a Nuclear Reaction enough PE
is lost that the mass loss is
measurable…unlike chemical
reaction.
51
Nuclear Fission and Fusion
Δ PE + Δ KE =0
Fusion:
down
up
8 protons + 8 neutrons ------- 1 oxygen nucleus +
ENERGY
Nucleons moving closer together with the attracting Nuclear Force of Attraction
means the PE is going down greatly.. Energy given off is opposite of Binding Energy
The electrostatic PE goes up but the amount of energy is insignificant
Fission: A nucleus splits and becomes pieces whose binding energy is greater.
8 protons
8neutrons
Individual protona and neutrons
236.90814 AMU
16.12752 AMU
BE
BE
Exothermic
PE
PE
A nucleus
Binding Energy:
Energy required to
take something apart
U235
16.0000 AMU
2
E=
MC
Δ
BE
235.12517AMU
FISSION
Kr
and Ba
Exothermic
Even less mass
Going from Lower Binding Energy to Higher
is Exothermic
If a reaction moves toward more binding energy/nucleon then PE may go down and energy must be given off: exothermic
52
Nuclear Fusion and The Death of a Star
(As gravitationally attractive bodies get
closer together their PE drops.)
Δ PE + Δ KE = 0
Nucleons
Hydrogen
PE
Helium
Heavy elements
Iron
Mass loss
Gravitational attraction produces enough heat to begin
fusion of H to He in the sun. Actually in the processs of
being formed in the collapse of Hatoms the
Gravitational PE dropsand a great deal of heat is
produced. This heat causes the fusion to take place
which produces another dropin PE and even more heat.
(physics books refer to Binding Energy per nucleon to
“explain” what happens.)
When H fuel is expended further collapse of the sun
in which PE drops even more produces a great deal
more heat and begins the fusion of He to elements up to
iron.
When He fuel is gone the sun collapses under the force of gravity and Gravitational PE goes down even more
which further raises the temperature BUT the next fusion reaction to heavier elements is endothermic so there
is not enough KE to cause fusion…in a sun 100x our sun the collapse continues rapidly and a great burst of
heat is given off as the sun core density becomes VERY large….a supernova has produced enough energy to
fuse the heavier elements in the periodic chart and incidently produce the mass difference between products
and reactants.
53
Water
PE
Unique properties
When water freezes..attracting bodies
get closer together and PE goes down
Liquid
just like everything else. However, ice
floats. How can the density get less but
Solid
molecules get closer together?
WATER
The strongest bonding in water is
hydrogen bonding…in the process of
freezing the bonds involved in hydrogen
bonding do get closer together as the
same time the average distance between
molecules get larger…dispersion force
energy actually does go up a little.
54
Student questions:
1. How does compressing a gas increase PE when molecules
are actually getting closer together? Attracting forces are
not a factor in increasing gas pressure….work must be
done on the gas to compress it.
2. How does compressing a spring increase PE: Moving
atoms either side of their equilibrium position will increase
the PE within the solid…attraction results in more PE when
its stretched and repulsion results in more PE when
compressed.
55
www.physchem.info
[email protected]