Transcript Unit 4 Nature_Of_Matter

Physics 30 Unit 4 Review
The Nature of Matter
and Radioactivity
The Nature of Matter
Atomic Theories:
indivisible part of
The Greeks: The atom is the smallest, ____________
an element that can still be called an element.
Thomson:
negative
•Discovered that the electron has a _____________
charge
charge to mass
and also found the ____________________
ratio of the
electron.
cathode ray
•He performed his experiments with ____________________
tubes.
raisin bun
•His model of the atom is called the _________________
model.
Formulas:
CRT
x x x
x x x
Fm = Fc
2
mv
qvB =
r
q
v
=
m Br
Remember:
F = ma
2
v
ac=
r
mv2
Fc= r
Mass Spectrometer:
Velocity Selector
Perpendicular Electric
and Magnetic fields
+
Charged
particles
X
X
X
𝐸=𝐸
1
𝑉𝑞 = 𝑚𝑣 2
2
X
X
X
X
X
X
X
X
X
X
X
X
_
If accelerated by a potential
difference then the
formulas are:
Ion Separator
Just a magnetic or
electric field
If the particles travel
through undeflected, then
the formulas are:
𝐹𝑚 = 𝐹𝑒
𝑞𝑣𝐵 = 𝐸 𝑞
Formulas are:
𝐹𝑚 = 𝐹𝑐
𝑚𝑣 2
𝑞𝑣𝐵 =
𝑟
Properties of Cathode Rays:
•Cathode rays have the same properties no matter which
metal
type of ____________
is used for the cathode.
straight
•Cathode rays travel in ______________
lines.
electric
E
•Cathode rays can be bent in both _________________
magnetic B
and ___________________
fields.
•Cathode rays can cause chemical reactions similar to
light
_______________
(develop photographic film).
•Cathode rays leave a vapour trail when they pass through
gas chamber
bubble chamber
a _________________
as well as a ___________________.
electrons
•Cathode rays are ________________.
Thomson Example:
A negatively charged particle is travelling with a speed of
1.43x106 m/s through a magnetic field of 2.50x10-3 T. The
particle follows a curved path of radius 3.25x10-3 m. What is
the charge to mass ratio of this particle?
Fm = Fc
mv2
qvB = r
6 m/s
q
v
1.43x10
=
m = Br
(2.5x10-3 T) (3.25x10-3 m)
= 1.76x1011 C/kg
Millikan’s Oil Drop Experiment:
negatively charged oil drops between
•He balanced ______________
electric plates. When the particles were suspended, the
electric
gravitational force.
____________
force equaled the _____________
+ plate
Fe
- Oil drop
Fg
- plate
Millikan’s Oil Drop Experiment (Formulas):
•If the oil drop is suspended: •If the oil drop accelerates up:
Fe = Fg
E q = mg
•If the oil drop moves with a
constant speed up or down:
Fe = Fg
E q = mg
Fe = Fg + Fa
E q = mg + ma
•If the oil drop accelerates down:
Fe = Fg - Fa
E q = mg - ma
Millikan’s Oil Drop Experiment (Graphing):
•Oil drops of different weights are suspended between electric
plates requiring different electric field strengths
Millikan’s Oil Drop Experiment (Graphing):
Line of best fit should:
• Average the data points the best
• Go through as many points as possible
• You can leave some points above
and below the line.
Weight of Oil
Drops
(x10?? N)
Slope Calculation:
Electric Field Strength
(x10?? N/C)
Fe = Fg
E q = mg
mg
= q = eE
• Try not to choose data points
• Choose points as far apart
as possible
Rutherford’s Scattering Experiment:
Rutherford’s Planetary Model:
scattering
•Rutherford performed a ______________
experiment.
alpha
•____________
particles were aimed at a layer of thin gold.
photographic film.
•The particles were detected by ______________
•He concluded that the nucleus is:
tiny
•Very ____________
positive
protons
•Contains ________________
charges called __________.
electrons orbit the nucleus like planets orbit the sun.
•__________
Rutherford’s Planetary Model (Formulas):
electric
•There is an _______________
force between the
negative
positive
__________electrons
and __________protons.
This is because
opposite
______________
charges attract.
•Since this force acts inwardly as the electron travels around
centripetal force.
the nucleus, it is also equal to the ____________
Example: Calculate the speed of the electron as it orbits the
nucleus of a hydrogen atom if it’s orbital radius is 5.29x10-7m.
Fe = Fc
kqq = mv2
r
r2
9 )(1.6 × 10−19 )(1.6 × 10−19 )
(8.99
×
10
v=
= 2.19x104m/s
−7
−31
5.29 × 10 (9.11 × 10 )
Maxwell’s Problem:
•According to Maxwell, any accelerating charge produces
light (c)
_____________
which travels at the speed of ___________.
EMR
•This can be shown with symbols:
∆ Ε
Δ𝐵
∆ Ε
•Since the electron in an atom is traveling in a circular path (it’s
direction
_____________
is always changing) it can be considered to be
accelerating even though it’s speed is constant.
•The electrons within atoms are accelerating charged particles.
EMR
They should give off _____________
(a form of energy) as they
travel. They should thus lose energy and collapse into the atom.
Bohr Model of the Atom:
•Within certain orbitals (a certain distance from the nucleus),
EMR
electrons are free to travel without giving off any ___________.
energy
•These orbitals are also called ___________
levels. The lowest
ground
energy level (closest to the nucleus) is called a ______________
state. The energy required to free the electron from the atom
ionization
is called the _______________
energy.
EMR
•When electrons drop energy levels, they give off ___________.
When electrons move up energy levels, they have either been hit
by an ___________
electron or an ______________.
EMR photon
Formulas used with the Bohr Model:
ℎ𝑖𝑡 𝑏𝑦 𝑎𝑛 𝑒 −
or photon
𝐸𝑀𝑅 𝑔𝑖𝑣𝑒𝑛 𝑜𝑓𝑓
positive
negative
•Energy levels can be written as ____________
or ____________
numbers.
subtract
•_____________
the energy levels to find the energy difference
between orbitals.
EMR Formulas
𝜀=
ℎ𝑐
𝜆
𝜀 = ℎ𝑓
e- Formulas
𝜀 = 𝑉𝑞
1
𝜀 = m𝑣 2
2
Hydrogen Atom:
•If the electron drops to the first (lowest) orbital, then
ultraviolet
_______________
is most likely released.
•If the electron drops to the second orbital, then
visible light
_______________
is most likely released.
•If the electron drops to the third orbital, then
infrared
_______________
is most likely released.
Continuous Spectra:
•Light from a hot glowing solid (like an incandescent light bulb)
will produce a continuous spectrum in the visible region.
Prism
White light
Diffraction Grating
𝑟
o
y
g
b
i
v
White light
𝑟
v
𝑣
r
Smaller wavelengths (blue) light is
refracted more.
Longer wavelengths (red) light is
diffracted more.
Blue bends more.
Think of the sky – it’s blue because
the red light light is diffracted more.
Emmission Spectra:
electrons
•Light from an excited elemental gas (excited by ___________
passing through it) will emit certain wavelengths of light. If this
bright
light is passed through a diffraction grating, a ______________
line pattern will be produced. Each element has a
unique
_____________
pattern.
Absorption Spectra:
•When light passes through a cool elemental gas, certain
wavelengths of light are absorbed. These will appear as
______________
dark
_________
lines on a spectrum.
Example:
What is the wavelength of EMR released when an electron within
an atom drops from an energy level of 12.0 eV to 8.5 eV?
E= 12.0 eV – 8.5 eV = 3.5 eV
𝐸=
ℎ𝑐
𝜆
𝜆=
ℎ𝑐
𝐸
(4.14 × 10−15 )(3.00 × 108 )
𝜆=
3.5𝑒𝑉
𝜆 = 3.55 × 10−7 m
Compton Effect:
•He performed a scattering experiment where EMR
photons
(___________)
were fired at electrons. He found that the
electrons moved off with speed after the collision and that the
longer
scattered x-rays had a ______________
wavelength.
•He concluded that EMR can have a mass property:
momentum
___________________.
•Momentum formula for masses:
•Momentum formula for EMR:
•The biggest angle an x-ray can
be scattered is straight back
180o
_________
𝑝 = 𝑚𝑣
𝑝=
ℎ
𝜆
Δ𝜆 =
ℎ
(1
𝑚𝑐
𝐸 = 𝑝𝑐
− 𝑐𝑜𝑠𝜃)
Example:
An X-Ray of wavelength 0.0500 nm scatters at an angle of 300.
Calculate the wavelength of the scattered photon.
30o
Δ𝜆 =
ℎ
(1
𝑚𝑐
Δ𝜆 =
6.63×10−34
(9.11×10−31 )(3.00×108 )
− 𝑐𝑜𝑠𝜃)
(1 − 𝑐𝑜𝑠30)
Δ𝜆 = 3.25 × 10−13 m
𝜆𝑓 = 𝜆𝑖 + Δ𝜆 = 0.0500 × 10−9 + 3.25× 10−13 = 5.03× 10−11 𝑚
de Broglie Wavelength:
•Proposed that masses can have an EMR property:
wavelength
___________.
•Objects with mass and speed travel with a ______________.
wavelength
The effect is only detectable for very small masses traveling at
high speed. The formula below should be given to you on a
diploma exam.
𝑝𝑚𝑎𝑠𝑠𝑒𝑠 = 𝑝𝐸𝑀𝑅
𝑚𝑣 =
𝜆=
ℎ
𝜆
6.63 × 10−34
ℎ
𝑚𝑣
𝑚𝑎𝑠𝑠 𝑎𝑛𝑑 𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒
Example:
Calculate the wavelength of an electron that has been
accelerated through a potential difference of 2 000 V using the
de Broglie wavelength formula 𝜆 = ℎ
𝑚𝑣
𝜆=
6.63×10−34
9.11×10−31 (??)
𝜀= 𝜀
1
𝑚𝑣 2 = 𝑉𝑞
2
𝜆 = 2.75 × 10−11 𝑚
𝑣=
𝑣=
2𝑉𝑞
𝑚
2(2000𝑉)(1.6 × 10−19 )
9.11 × 10−31
𝑣 = 2.65 × 107
Electron Orbitals:
•Electrons really travel in a ____________
pattern as they
wave
travel around the nucleus of the atom.
•There must be a whole number multiple of wavelengths as
nucleus
the electron orbits the ___________.
𝑛𝜆 = 2𝜋𝑟
You do not have to memorize
this formula for the diploma.
The Standard Model of the Atom:
•Particles responsible for Forces are called
boson
______________
particles.
Boson
•______________
particles responsible for the following
Forces (listed from strongest to weakest):
•The strong nuclear force: __________________
gluons
•The electromagnetic force: __________________
photons
•The weak nuclear force: __________________
W+ W- Zo
graviton
•The gravitational force: __________________
(undetected)
The Standard Model of the Atom:
•Particles that make up matter are called ______________.
fermions
•Very small particles that are elementary particles are
leptons
called ___________________.
The electron and it’s
leptons
neutrino are _________________.
•Larger particles, like neutrons and protons are called
hadrons
___________________.
They are made up of
quarks
___________________.
•_____________
are made up of 2 quarks.
Mesons
•_____________
baryons
are made up of 3 quarks.
The Standard Model of the Atom:
uud
•Protons are made up of the following quarks: _____________
1
n
0
1
+
p
1
0𝛽
-1
+
𝜐
udd
•neutrons are made up of the following quarks: _____________
1
p
1
1
+
n
0
0𝛽
1
+
𝜐
Radioactivity:
half
•Particles that undergo radioactive decay, lose __________
their
mass over a certain period of time. This time is called
half life
_________________.
•During this process, a radioactive element changes into
another element, giving off particles or EMR. This is
called __________________.
transmutation
•Formulas:
Graphing Radioactivity:
Bq
•Radioactivity has lots of different units: __________,
Bq/s
rads
decays / s
___________,
____________,
______________
to list a few.
Terms:
neutron or a proton
Nucleon: __________________________
number of protons (bottom number)
Atomic Number: _______________
The atomic number identifies the element.
number of protons and neutrons (top number)
Mass Number: _______________
the sum of the top numbers on both
Conservation of Nucleons: _____________________________
___________________________________________________
sides of an equation must be equal.
the sum of the bottom numbers on
Conservation of Charge: _____________________________
___________________________________________________
both sides of an equation must be equal.
3 Types of Radioactivity:
1. Beta Decay: assume beta negative for just “beta decay”
Beta Negative Decay: is an _________________.
electron
0𝛽
𝑒-1
-1
symbols are: __________________
𝜐
an antin-eutrino is also released _________.
Example: Write the decay equation for carbon 14 emitting a
beta negative particle.
14
c
6
14
+
N
7
0𝛽
-1
+
𝜐
3 Types of Radioactivity:
Beta Positive Decay: is an _____________________________.
antimater electron (positron)
0
1𝛽
symbols are: __________________
𝜐
a neutrino is also released __________.
Example: Write the decay equation for carbon 14 emitting a
beta positive particle.
14
c
6
14
+
B
5
0𝛽
1
+
𝜐
3 Types of Radioactivity:
2. Alpha decay: is the nucleus of a ____________
helium
atom.
4 2+
4
2+
Symbols are: ___________________
2𝛼
2𝐻𝑒
Example: Write the decay equation for nitrogen 15 emitting an
alpha particle.
15
7𝑁
4 2+
2𝛼
+
11
5𝐵
3 Types of Radioactivity:
3. Gamma decay: is a high energy, high ____________,
frequency small
wavelength
______________
EMR photon.
0
𝛾
Symbol is: __________________
0𝛾
Example: Write the decay equation for cobalt 56 emitting a
gamma ray.
56
27𝐶𝑜
𝛾 +
56
27𝐶𝑜
Penetrating Ability:
In order of increasing ability to penetrate objects:
thick paper or cardboard
Alpha particles: ___________________
Beta particles: ___________________
thin metal
lead (dense metal)
Gamma Rays: __________________________
Ability to Ionize (danger / risk):
In order of increasing risk:
higher energy due to increased speed
Beta particles: __________________________
higher energy due to larger mass
Alpha particles: __________________________
higher energy due to larger frequency
Gamma Rays: __________________________
or smaller wavelength
Binding Energy:
neutrons of an atom to hold
•Is the energy exerted by the ___________
the ______________
charged protons tightly in the nucleus.
positively
•Some mass of the ___________
neutrons
is converted into energy.
•Formula:
Example: The mass of a lithium-7 nucleus is 7.015989 u.
What’s the binding energy?
7
Li
3
3𝑝+ = 3(1.6726 × 10−27 𝑘𝑔)
4𝑛 = 4(1.6749 × 10−27 𝑘𝑔)
1.17174 × 10−26 𝑘𝑔
7.015989𝑢 (1.66 × 10−27 𝑘𝑔/𝑢) = 1.16465417× 10−26 𝑘𝑔
1.17174 × 10−26 − 1.16465417 × 10−26 = 7.08583 × 10−29
𝐸 = 𝑚𝑐 2 = 7.08585 × 10−29 3.00 × 108
2
= 6.38 × 10−12 𝐽
Nuclear Fission:
splitting
•Is the ____________
of an atom into other elements.
nuclear
•Is the process used in ________________
power plants.
•Formula:
Example: Calculate the energy produced in the following fission reaction.
235
1
U + 0n
235
140
U=3.9029x10-25 kg
1
-27
0n =1.6749x10
kg
140
Xe=2.3234x10-25 kg
94
Sr =1.5595x10-25 kg
Xe +
94
Sr
1
+ 2 0n Mass of reactants 3.919649 × 10−25
Mass of products 3.916398 × 10−25
Mass difference
3.251 × 10−28
Binding Energy E=mc2
3.251 × 10−28 (3.00 × 108 )2
2.9259 × 10−11 𝐽
Nuclear Fusion:
•Is the ____________
fusing
of simpler atoms into heavier elements.
sun
•Is the process going on inside the ________________.
•Formula:
Example: Calculate the energy produced in the following fusion reaction.
2
1
3
H + 1H
4
2
2
-27 kg
1 H=3.4444x10
1
-27 kg
0n =1.6749x10
4
He =6.6463x10-27 kg
3
H
1
=5.0082x10-27 kg
1
He + 0n
Mass of reactants 8.4526 × 10−27
Mass of products 8.3212 × 10−27
Mass difference
1.314 × 10−28
Binding Energy E=mc2
1.314 × 10−28 (3.00 × 108 )2
1.1826 × 10−11 𝐽