Transcript Chapter 22 Nuclear Reactions

EOCT
Review
Energy
Transformations
Transfer of Energy
Heat is transferred
three ways…
Conduction
the movement of heat
energy through a
substance by direct
contact between the
particles
Ex. – a candle heats one end of a metal
rod and the other end gets hot because
of the transfer of heat
Convection
the transfer of heat
energy by the actual
movement (or currents)
of heated matter
Ex. – The water in the
bottom of a teapot
becomes hot creating
currents which carry heat
upward
Radiation
transfer of heat energy
by waves from an area
of high temperature to
an area of low
temperature
Ex. – Heat from a space
heater, fireplace, or the sun
is the spontaneous release of
energy and particles from the
nucleus of an atom.
ISOTOPES
 Atoms of the same element
with a different number of
neutrons.
 Ex: carbon-12 & carbon-14
 Carbon-12
 6 protons
 6 neutrons
 6 electrons
 Carbon-14
 6 protons
 8 neutrons
 6 electrons
The nucleus of an atom can be
unstable is there are too many
neutrons for the number of protons.
An unstable nucleus will be
radioactive.
All elements with an atomic
number greater than 83 are
radioactive
3 Types of Radioactivity
Radioactive Decay
 ALPHA PARTICLE (α)
 BETA PARTICLE (β)
 GAMMA RAYS (γ)
ALPHA
PARTICLE
 2 protons & 2 neutrons
 nucleus of a helium atom
 weakest type of radiation
 can be stopped by a piece of paper
 12 inches max. distance travel
What happens to the numbers
of particles in the nucleus after
alpha decay?
BETA
PARTICLE
 an electron emitted from the nucleus
 A neutron splits into a proton & electron
 The electron is expelled out of the nucleus
 The proton stays and increases the number of protons
by one.
 The atomic number of the element increases by one
 The element changes into the next higher element on
the periodic table.
 100x stronger than an alpha particle
What happens to the numbers of particles in
the nucleus after beta decay?
Gamma Rays
 An electromagnetic wave
 A packet of energy
 The energy readjustment in the nucleus
 Most powerful form of radiation
 The sun is a great source of gamma radiation
Gamma Ray Photography From Space
Antoine
Henri Becquerel
 In 1896, radioactivity was
first discovered.
 Used uranium salts = placed
them near a photographic
film plate.
 exposed the film (below)
 Awarded Nobel Prize in
1903 in Physics
Pierre & Marie Curie (1898)
 Discover the radioactive properties of radium & polonium
 Together awarded the Nobel Prize in 1903 (physics) along
with Henri Becquerel
 Marie is award a second Nobel Prize in 1911 (chemistry)
 Pierre is killed in an accident in 1906, Marie continues
working with radioactive substances.
Transmutation
 = changes from one element to another
element during α and β decay.
 Alpha Decay = mass number decreases
by 4 and the atomic number decreases by
2
 Beta Decay = mass number does not
change and the atomic number increases
by 1
Alpha Decay
 Uranium-238 has 92 protons
 After alpha decay
(2 protons & 2 neutrons leave the nucleus)
 Becomes Thorium-234 and has 90 protons
Beta Decay
 Carbon-14 has 6 protons & 8 neutrons
 After beta decay (a neutron is split into a proton and electron
& the electron is expelled from the nucleus)
 Becomes Nitrogen-14 and has 7 protons and 7 neutrons
Half Life
= the time it takes for one half of the mass of a
radioactive substance to decay.
Ex: carbon-14 = 5730 years
100 gram sample
– In 5730 yrs = 50 grams C-14 & 50 grams N-14
– In11,460 yrs = 25 grams C-14 & 75 grams N-14
– In 17,190 yrs = 12.5 grams C-14 & 87.5 grams N-14
The Decay of
Strontium-90
Number of half- Elapsed Time
lives
Amount of
strontium-90
present
0
0
10.0 g
1
29 years
5.0 g
2
58 years
?
?
?
.625g
Nuclear Reactions
Nuclear Fission
Nuclear Fusion
Nuclear Fission
 = the splitting of the nucleus into two smaller
nuclei
 Neutrons are used to split the nucleus
 Additional neutrons are released to continue on
to hit/split other nuclei
Chain Reactions
 Critical Mass (required) = concentration of
radioactive atoms in a sample.
Controlled Chain Reaction = many of the
neutrons that are produced are absorbed in “control
rods” prevent excess energy to be released.
Ex. Nuclear Power Plants
Uncontrolled Chain Reaction = all the neutrons
are allowed to continue to hit/split other nuclei
causing massive amounts of energy to be released
all at once.
 Ex. Atomic Bomb (used on Japan in 1945)
Controlled Chain Reaction
Uncontrolled Chain Reaction
Nuclear Fusion
 = the joining of two smaller nuclei into a single
larger nucleus
 Extremely more powerful release of energy
than fission
 Requires a temperature of 10 million degrees
Celsius
 Also known as a thermonuclear reaction
 ex: H-bomb and the sun/stars
Fusion Explosions
World War Breaks out in Europe in 1939
Szilard drafted a letter in consultation with Albert
Einstein that was addressed from Einstein to
President F.D. Roosevelt and which warned
him of the possibility of nuclear weapons (the
"Einstein Letter").
This letter was delivered to FDR on October 11,
1939, and ten days later the first meeting of the
Advisory Committee on Uranium (the "Briggs
Uranium Committee") was held in Washington,
DC on Pres. Roosevelt's order.
“The Gadget”
Code Name =
Trinity
 July 16, 1945 - At 5:29:45
a.m. “The Gadget” was
detonated in the first atomic
explosion in history. The
explosive yield was 20-22
Kt, vaporizing the steel
tower.
August 6, 1945
 “Little Boy” is used on
Hiroshima, Japan
 Dropped from the B-29
bomber named “The Enola
Gay”
 5 mile circle of destruction
 est. 78,000 killed & 70,000
injured
August 9, 1945
 “Fat Man” is used on
Nagasaki, Japan
 2 mile circle of
destruction
 40,000 killed &
25,000 injured
 Japan
unconditionally
surrenders a few
days later & WWII is
officially over
Further Nuclear Developments
 August 1949 = Soviet Union tests their first
atomic bomb after spies deliver US secret
bomb blue-prints
 November 1952 = United States the first
Hydrogen bomb (H-bomb) 10 MT in strength,
USSR tests their first H-bomb in Aug. 1953
 Other Atomic weapons countries include Great
Britain, China, France, India, Pakistan, and
possibly Israel. North Korea and Iran are
currently in the news for seeking nuclear
capabilities.