Manhattan project
.
fusion/fission
I- FUSION / FISSION
1)
In stars hydrogen atoms fuse together to produce helium and heavier elements.
That's why Karl Sagan said we are the dust of stars. The atoms that build us and everything in our solar system,
were made in a giant star. ( the solar system is believed to form after the explosion of a giant star or supernovae.
The solar system is made of the debris of that explosive star)
When 2 atoms fuse together (need high temperature and high pressure environment),
to produce a new element(helium is formed when nuclei of hydrogen fuse together), a huge amount of energy
is produced in the form of radiation. (visible light, infra red, gamma rays .... ).
During the process, some matter is transformed into energy. That is, the total mass of the products
is less than the total mass of the reactants. The loss of mass = gain in energy.
The energy produced by a fusion reaction can be computed by the famous Einstein formula:
E = m c2 where c is the speed of light c = 300,000,000 m/s , m is the mass lost my the reactants (kg) and
E is the equivalent energy in joules.
The equation tells you that mass (or matter like a particle) can becomes energy and energy can become mass (matter).
For example, in a fusion reaction some of the mass of the reactants will be changed into energy (radiation).
Take this equation of fusion for example:
2 hydrogen nuclei + 2 neutrons = 1 helium nucleus + energy
find the total mass of the reactants. m = ________ g / mole = _______ kg (2 masses of H and 2 masses of neutrons)
use : mass of 1 neutron = 1.0087 g/mol
mass of hydrogen is to be found in the periodic table.
find the total mass of the product (helium) = __________ g/mol = ______kg (see periodic table)
Is the mass the same ? Compute the difference = ∆m = __________ kg/mol
What did happen to this mass ? Find the energy produced by the reaction ∆E = ∆m c2 in joules/
Is this a big number? this because you multiply by the square of ________.
2)
Lisa Meitner is the scientist who understood how to trigger a fission reaction./
However, she didn't get full credits for it. Instead her ex colleague Otto Hahn (from Kaiser Wilhelm Institute, Germany)
got the Nobel prize (chemistry) in 1944 and didn't share it. Lisa Meitner was newish and began her career in
Germany before the rise of the Nazis. She was safe for a while because of her Austrian citizenship but
was forced to flee to Holland and then Sweden (when the Nazis occupied Austria).
She did regret to have stayed in the institute while the Nazis were in power. Otto Hahn took
full credits for the discovery and didn't mention her name when he received the prize.
Letters between Otto and Lisa showed that she is the one who understood the process.
She was offered to work with Oppenheimer on the Manhattan project but declined since
she didn't want to be involved in the building of an atomic bomb. (note :Oppenheimer, director of the Manhattan project said
looking at the explosion: "God bless us, we have created something more awful than hell". )
She came with the idea that shooting a neutron at an unstable atom like uranium will produce
fission fragments (other elements / particles) and a huge amount of energy.
This is because uranium is unstable and will decay in another element.
In the process, some mass will be transformed into energy .
Very much like for the fusion reaction.
The energy can be computed thanks to Einstein formula E = m c2 . The formula shows
that matter (like a particle or a piece of an atom) can become pure energy (like radiation).
Note: the opposite is also true. pure energy can also become matter. (In a collider atoms are
smashed together and become pure energy and then energy becomes new particles)
consider the fission:
neutron + Uranium 235 = Barium 140 + Krypton 83 + 2 neutrons
(neutron is the projectile and uranium 235 is an isotope of uranium 238. it has 3 less neutrons than uranium 238)
The mass of a neutron is 1g/mol, mass of uranium 235 is 235g/mol ....
Find the loss in mass that occurred during this reaction. m = _______ g = __________ kg
Use Einstein equation to find the energy produced by the reaction. (mass lost = energy = mc2)
(mass transformed into energy). Use the periodic table.
3) We use fission in a nuclear reactor to produce electricity. We collect the energy produced
due to the transformation of some of the mass of Uranium235. (conversion of mass to energy) .
This is still a fission a reaction, except now we control the chain reaction
Observe the image below. In a bomb, the 3 neutrons
produced by the fission will become 3 projectiles ready to hit another atom of uranium.
Each one will produce 3 other neutrons so 32 projectiles after the second generation., then 33 after the third generation...
For those who are taking Algebra 2, this is called an exponential growth. In a reactor, carbon rods
absorb some of the neutrons so the chain reaction stays under control.
The advantage is that you just need a tiny bit of uranium to get a huge amount of energy.
No greenhouse gases are emitted. Here is an example to grasp the difference:
To prepare popcorn you need to give the microwave 200 KJ. To get that much of energy you need
10 to 20 g of coal but only 2 micrograms of uranium. Find the ratio between mass of coal and mass of uranium.
(convert micrograms to grams first). ratio = ___________ so you need ______times more coal than uranium.
You can use uranium 238 (natural one) or uranium 235 (processed, enriched).
If you use U 238, you need 140g of it to sustain an average household in electricity during 1 year.
If you use coal, you need 3 tons (3000kg) to sustain the same household. (same time)
what's the ratio ? _____________. (convert kg to g) Is it the same order of magnitude than before ?____
about what power of ten ? (10 ? 102? 103? 104 ? ) __________-
If you use enriched uranium U235, you need only 0.3 g of it to sustain the household for 1 year.
What's the ratio now ? ________ or 10__ .
The draw back are the waste products that are also radioactive. However, if stored properly, the radiations
are contained. The radioactivity will decrease with time. (as plutonium also decay). The worry is that
plutonium can be used to build atomic weapons. (Nagasaki was destroyed by a plutonium bomb).
(although it is harder to build a plutonium bomb than an uranium bomb with U235)
4) 1 g of coal produces 29KJ
1g of Uranium 235 produces 96 400 000KJ
Find the ratio _________ or about 10__
5) When water (H2O) undergoes a phase change from liquid to solid (ice) , bonds between water molecules form
(hydrogen bonds) and energy is produced. The potential energy (binding energy, bonds between molecules) goes
into heat (kinetic energy, energy of motion of molecules) . The molecules can not move freely as before (liquid).
The change in energy per gram of water is - 6.03KJ. This change is a physical change because no bond between the atoms of H2O
are broken. The binding is due to the electric force between the molecules of water that are polarized.
(one side of the molecule is + and one side is - )
(it is a negative energy because the system (1 g of H20) loses energy. )
When hydrogen gas (H2) reacts with oxygen gas (O2 ) to produce water H2O (H2 + 1/2 O2 =H2O)
it is a chemical reaction and it involves the electrons (from outside shells) of the atoms forming covalent bonds.
The reaction is exothermic and chemical potential energy is converted into heat. The system (1g of H20) loses energy
such as the loss is -241.8KJ per gram of water formed. It is a chemical change.
The bonding is possible because of the electric force between the electrons of the outside shells and the nuclei.
When, like in a star, an hydrogen atom fuses with a deuterium atom (isotope of hydrogen) an helium atom results.
It is a nuclear change. hydrogen + deuterium = helium . The system loses energy . potential energy is changed into radiation (heat).
The loss is huge, for 1 g of helium formed = - 529,000,000KJ. ( it is also what happens in a thermonuclear weapon)
The bonding is possible because of the strong force between the protons and the neutrons.
The strong force holds all the nucleons together inside the nucleus.
Answer these questions :
A) When water change from a liquid to a gas,it is a ___________ change/ (nuclear ? physical ? chemical ? ).
the bonds between the molecules of water are _________ in ice than in liquid water (weaker ? stronger ? ).
These bonds are due to the work of the _________ force between the polarized molecules.
B) When hydrogen gas reacts with oxygen as to produce water, the change is said to be ____________. (nuclear ? physical ? chemical?).
The new bonds formed are between ________ (atoms ? molecules ? nucleons)/ The reaction is endothermic or exothermic ?_________
The bonds form because of the work of the electric force between the electrons and the _____________.
C) when hydrogen atoms fuse together, it is a ___________ change. the bonds formed are between the ___________ (molecules? nucleons?
atoms ?). it involves the _______ _________ force.
D) inside a helium nucleus, ___________ bonds hold the nucleons together (molecular ? nuclear ? covalent (between atoms) ?)
Inside a molecule of oxygen gas O2, a ___________ bond holds the 2 atoms together. (the glue is the electrons)
between the molecules of water , inside a crystal of ice, __________ bonds hold the crystal together.
E) which change produces the greatest amount of energy ? _________ ( physical ? chemical?nuclear ?)
To break bonds (between molecules, atoms or nucleons) you need to bring energy. (do the reverse).
Which change require more energy :
pulling the nucleons of helium apart ? (breaking the nuclear bonds), pulling hydrogen apart from oxygen in a water molecule H20
(breaking the covalent bond) ? or melting ice (breaking the molecular bonds) ?
Melting ice is easy, you _____________ and you bring _______ KJ per g of H20.
How can you break water molecules into O2 and H2 ? (it is called electrolysis) .
__________________________ You bring _____ KJ of energy.
This you do do in your kitchen. Can you ,that easily, break helium into small parts ? this demands
a huge amount of energy. You need an atom smasher. What is the device that can break atoms ?
and how it works ? ____________________
(the brand new one is underground between France and Switzerland, you have one in Chicago in the Fermi lab).
Did you know President Bush cut drastically the budget of the Fermi lab ? leaving the European with
better tools to do theoretical Physics ?
F) what's the ratio between the energy produced by the nuclear fusion of hydrogen and the energy produced
when O2 combine with H2 to produce water ?
G) When gasoline is burnt to produce electricity (or coal), what kind of change is it undergoing ?_______________
(gas + oxygen = water + pollution (like carbon dioxide, sulfur dioxide, carbon dioxide ..)
H) Although it is very hard to break helium apart (very stable atom), some atoms will do just that on their own.
And the reaction also produces energy and involves ______ forces. (electric ? nuclear? )
The reaction is called ______________ decay. (collaborative ? radioactive ? annoying ?).
This is because the atoms are sometime unstable , like uranium, and they will spontaneously decay producing
energy and matter (uranium can becomes lead at the end of a chain of decays). The energy produced is in the form of
___________ ( angels ? radiation ? shtroupf ? ). You can also trigger this fission reaction by shooting ________ at an
unstable atom. ( shtroupf ? cookies? neutrons ? test tubes ? ). In a nuclear reactor uranium becomes plutonium after
a _______ is shot at it. What kind of change is that ? __________. Will you produce more energy with 1 g of uranium
or 1 g of gasoline ? _________ how many times more ? ________ (see table at the beginning of the unit)
6) In a atomic bomb (fission ) potential energy is transformed to kinetic energy through a chain reaction.
as shown here : discuss.
more on neutrons, atomic bombs and nuclear reactors on this website
7) more on nuclear reactor
A nuclear reactor can not explode like an atomic bomb.
Even if the chain reaction is out of control (like for Chernobyl),
the chain reaction will stop and the reactor explodes like TNT.
There is not the necessary critical mass of uranium 235 to keep the chain reaction going up to the 80th generation
so you can't get an atomic bomb. What happened in Chernobyl is very unlikely to happen again as we don't use
moderators made of graphite anymore. These moderators tend to burn. We mainly use water to moderate
the chain reaction and to sustain it. We can use light water (with hydrogen) or heavy water (with deuterium).
plus the Chernobyl reactor was not contained.
Enrico Fermi figured out how to use fission to produce thermal energy without trigerring an atomic explosion.
A nuclear reactor uses natural uranium made of mostly U238. It also contains U235 but if it is not enriched,
it contains less than 1% of U235.
The big idea of Fermi to slow down the neutrons using moderators. These slow neutron can split U235 and a
chain reaction is sustained. The slow neutrons tend to bypass U238. When neutrons are absorbed by U238,
U238 becomes U239 that decays into plutonium 239.
When the neutrons slow down they lose kinetic energy than heat up the water. The heat is used to produce water vapor
that turns a turbine. This how electricity is produced. The decay of U238 also produces heat.
If light water is used U235 is needed as water tend to absorb the neutrons. So uranium is enriched to 3 to 7%.
(instead of .75%).
If heavy water is used, natural uranium can be used are the neutron are not absorbed that much.
more about it
more about fission
here to learn more about it
source: http://www.sparknotes.com/math/precalc/conicsections/section1.rhtml
.
fusion/fission
I- FUSION / FISSION
1)
In stars hydrogen atoms fuse together to produce helium and heavier elements.
That's why Karl Sagan said we are the dust of stars. The atoms that build us and everything in our solar system,
were made in a giant star. ( the solar system is believed to form after the explosion of a giant star or supernovae.
The solar system is made of the debris of that explosive star)
When 2 atoms fuse together (need high temperature and high pressure environment),
to produce a new element(helium is formed when nuclei of hydrogen fuse together), a huge amount of energy
is produced in the form of radiation. (visible light, infra red, gamma rays .... ).
During the process, some matter is transformed into energy. That is, the total mass of the products
is less than the total mass of the reactants. The loss of mass = gain in energy.
The energy produced by a fusion reaction can be computed by the famous Einstein formula:
E = m c2 where c is the speed of light c = 300,000,000 m/s , m is the mass lost my the reactants (kg) and
E is the equivalent energy in joules.
The equation tells you that mass (or matter like a particle) can becomes energy and energy can become mass (matter).
For example, in a fusion reaction some of the mass of the reactants will be changed into energy (radiation).
Take this equation of fusion for example:
2 hydrogen nuclei + 2 neutrons = 1 helium nucleus + energy
find the total mass of the reactants. m = ________ g / mole = _______ kg (2 masses of H and 2 masses of neutrons)
use : mass of 1 neutron = 1.0087 g/mol
mass of hydrogen is to be found in the periodic table.
find the total mass of the product (helium) = __________ g/mol = ______kg (see periodic table)
Is the mass the same ? Compute the difference = ∆m = __________ kg/mol
What did happen to this mass ? Find the energy produced by the reaction ∆E = ∆m c2 in joules/
Is this a big number? this because you multiply by the square of ________.
2)
Lisa Meitner is the scientist who understood how to trigger a fission reaction./
However, she didn't get full credits for it. Instead her ex colleague Otto Hahn (from Kaiser Wilhelm Institute, Germany)
got the Nobel prize (chemistry) in 1944 and didn't share it. Lisa Meitner was newish and began her career in
Germany before the rise of the Nazis. She was safe for a while because of her Austrian citizenship but
was forced to flee to Holland and then Sweden (when the Nazis occupied Austria).
She did regret to have stayed in the institute while the Nazis were in power. Otto Hahn took
full credits for the discovery and didn't mention her name when he received the prize.
Letters between Otto and Lisa showed that she is the one who understood the process.
She was offered to work with Oppenheimer on the Manhattan project but declined since
she didn't want to be involved in the building of an atomic bomb. (note :Oppenheimer, director of the Manhattan project said
looking at the explosion: "God bless us, we have created something more awful than hell". )
She came with the idea that shooting a neutron at an unstable atom like uranium will produce
fission fragments (other elements / particles) and a huge amount of energy.
This is because uranium is unstable and will decay in another element.
In the process, some mass will be transformed into energy .
Very much like for the fusion reaction.
The energy can be computed thanks to Einstein formula E = m c2 . The formula shows
that matter (like a particle or a piece of an atom) can become pure energy (like radiation).
Note: the opposite is also true. pure energy can also become matter. (In a collider atoms are
smashed together and become pure energy and then energy becomes new particles)
consider the fission:
neutron + Uranium 235 = Barium 140 + Krypton 83 + 2 neutrons
(neutron is the projectile and uranium 235 is an isotope of uranium 238. it has 3 less neutrons than uranium 238)
The mass of a neutron is 1g/mol, mass of uranium 235 is 235g/mol ....
Find the loss in mass that occurred during this reaction. m = _______ g = __________ kg
Use Einstein equation to find the energy produced by the reaction. (mass lost = energy = mc2)
(mass transformed into energy). Use the periodic table.
3) We use fission in a nuclear reactor to produce electricity. We collect the energy produced
due to the transformation of some of the mass of Uranium235. (conversion of mass to energy) .
This is still a fission a reaction, except now we control the chain reaction
Observe the image below. In a bomb, the 3 neutrons
produced by the fission will become 3 projectiles ready to hit another atom of uranium.
Each one will produce 3 other neutrons so 32 projectiles after the second generation., then 33 after the third generation...
For those who are taking Algebra 2, this is called an exponential growth. In a reactor, carbon rods
absorb some of the neutrons so the chain reaction stays under control.
The advantage is that you just need a tiny bit of uranium to get a huge amount of energy.
No greenhouse gases are emitted. Here is an example to grasp the difference:
To prepare popcorn you need to give the microwave 200 KJ. To get that much of energy you need
10 to 20 g of coal but only 2 micrograms of uranium. Find the ratio between mass of coal and mass of uranium.
(convert micrograms to grams first). ratio = ___________ so you need ______times more coal than uranium.
You can use uranium 238 (natural one) or uranium 235 (processed, enriched).
If you use U 238, you need 140g of it to sustain an average household in electricity during 1 year.
If you use coal, you need 3 tons (3000kg) to sustain the same household. (same time)
what's the ratio ? _____________. (convert kg to g) Is it the same order of magnitude than before ?____
about what power of ten ? (10 ? 102? 103? 104 ? ) __________-
If you use enriched uranium U235, you need only 0.3 g of it to sustain the household for 1 year.
What's the ratio now ? ________ or 10__ .
The draw back are the waste products that are also radioactive. However, if stored properly, the radiations
are contained. The radioactivity will decrease with time. (as plutonium also decay). The worry is that
plutonium can be used to build atomic weapons. (Nagasaki was destroyed by a plutonium bomb).
(although it is harder to build a plutonium bomb than an uranium bomb with U235)
4) 1 g of coal produces 29KJ
1g of Uranium 235 produces 96 400 000KJ
Find the ratio _________ or about 10__
5) When water (H2O) undergoes a phase change from liquid to solid (ice) , bonds between water molecules form
(hydrogen bonds) and energy is produced. The potential energy (binding energy, bonds between molecules) goes
into heat (kinetic energy, energy of motion of molecules) . The molecules can not move freely as before (liquid).
The change in energy per gram of water is - 6.03KJ. This change is a physical change because no bond between the atoms of H2O
are broken. The binding is due to the electric force between the molecules of water that are polarized.
(one side of the molecule is + and one side is - )
(it is a negative energy because the system (1 g of H20) loses energy. )
When hydrogen gas (H2) reacts with oxygen gas (O2 ) to produce water H2O (H2 + 1/2 O2 =H2O)
it is a chemical reaction and it involves the electrons (from outside shells) of the atoms forming covalent bonds.
The reaction is exothermic and chemical potential energy is converted into heat. The system (1g of H20) loses energy
such as the loss is -241.8KJ per gram of water formed. It is a chemical change.
The bonding is possible because of the electric force between the electrons of the outside shells and the nuclei.
When, like in a star, an hydrogen atom fuses with a deuterium atom (isotope of hydrogen) an helium atom results.
It is a nuclear change. hydrogen + deuterium = helium . The system loses energy . potential energy is changed into radiation (heat).
The loss is huge, for 1 g of helium formed = - 529,000,000KJ. ( it is also what happens in a thermonuclear weapon)
The bonding is possible because of the strong force between the protons and the neutrons.
The strong force holds all the nucleons together inside the nucleus.
Answer these questions :
A) When water change from a liquid to a gas,it is a ___________ change/ (nuclear ? physical ? chemical ? ).
the bonds between the molecules of water are _________ in ice than in liquid water (weaker ? stronger ? ).
These bonds are due to the work of the _________ force between the polarized molecules.
B) When hydrogen gas reacts with oxygen as to produce water, the change is said to be ____________. (nuclear ? physical ? chemical?).
The new bonds formed are between ________ (atoms ? molecules ? nucleons)/ The reaction is endothermic or exothermic ?_________
The bonds form because of the work of the electric force between the electrons and the _____________.
C) when hydrogen atoms fuse together, it is a ___________ change. the bonds formed are between the ___________ (molecules? nucleons?
atoms ?). it involves the _______ _________ force.
D) inside a helium nucleus, ___________ bonds hold the nucleons together (molecular ? nuclear ? covalent (between atoms) ?)
Inside a molecule of oxygen gas O2, a ___________ bond holds the 2 atoms together. (the glue is the electrons)
between the molecules of water , inside a crystal of ice, __________ bonds hold the crystal together.
E) which change produces the greatest amount of energy ? _________ ( physical ? chemical?nuclear ?)
To break bonds (between molecules, atoms or nucleons) you need to bring energy. (do the reverse).
Which change require more energy :
pulling the nucleons of helium apart ? (breaking the nuclear bonds), pulling hydrogen apart from oxygen in a water molecule H20
(breaking the covalent bond) ? or melting ice (breaking the molecular bonds) ?
Melting ice is easy, you _____________ and you bring _______ KJ per g of H20.
How can you break water molecules into O2 and H2 ? (it is called electrolysis) .
__________________________ You bring _____ KJ of energy.
This you do do in your kitchen. Can you ,that easily, break helium into small parts ? this demands
a huge amount of energy. You need an atom smasher. What is the device that can break atoms ?
and how it works ? ____________________
(the brand new one is underground between France and Switzerland, you have one in Chicago in the Fermi lab).
Did you know President Bush cut drastically the budget of the Fermi lab ? leaving the European with
better tools to do theoretical Physics ?
F) what's the ratio between the energy produced by the nuclear fusion of hydrogen and the energy produced
when O2 combine with H2 to produce water ?
G) When gasoline is burnt to produce electricity (or coal), what kind of change is it undergoing ?_______________
(gas + oxygen = water + pollution (like carbon dioxide, sulfur dioxide, carbon dioxide ..)
H) Although it is very hard to break helium apart (very stable atom), some atoms will do just that on their own.
And the reaction also produces energy and involves ______ forces. (electric ? nuclear? )
The reaction is called ______________ decay. (collaborative ? radioactive ? annoying ?).
This is because the atoms are sometime unstable , like uranium, and they will spontaneously decay producing
energy and matter (uranium can becomes lead at the end of a chain of decays). The energy produced is in the form of
___________ ( angels ? radiation ? shtroupf ? ). You can also trigger this fission reaction by shooting ________ at an
unstable atom. ( shtroupf ? cookies? neutrons ? test tubes ? ). In a nuclear reactor uranium becomes plutonium after
a _______ is shot at it. What kind of change is that ? __________. Will you produce more energy with 1 g of uranium
or 1 g of gasoline ? _________ how many times more ? ________ (see table at the beginning of the unit)
6) In a atomic bomb (fission ) potential energy is transformed to kinetic energy through a chain reaction.
as shown here : discuss.
more on neutrons, atomic bombs and nuclear reactors on this website
7) more on nuclear reactor
A nuclear reactor can not explode like an atomic bomb.
Even if the chain reaction is out of control (like for Chernobyl),
the chain reaction will stop and the reactor explodes like TNT.
There is not the necessary critical mass of uranium 235 to keep the chain reaction going up to the 80th generation
so you can't get an atomic bomb. What happened in Chernobyl is very unlikely to happen again as we don't use
moderators made of graphite anymore. These moderators tend to burn. We mainly use water to moderate
the chain reaction and to sustain it. We can use light water (with hydrogen) or heavy water (with deuterium).
plus the Chernobyl reactor was not contained.
Enrico Fermi figured out how to use fission to produce thermal energy without trigerring an atomic explosion.
A nuclear reactor uses natural uranium made of mostly U238. It also contains U235 but if it is not enriched,
it contains less than 1% of U235.
The big idea of Fermi to slow down the neutrons using moderators. These slow neutron can split U235 and a
chain reaction is sustained. The slow neutrons tend to bypass U238. When neutrons are absorbed by U238,
U238 becomes U239 that decays into plutonium 239.
When the neutrons slow down they lose kinetic energy than heat up the water. The heat is used to produce water vapor
that turns a turbine. This how electricity is produced. The decay of U238 also produces heat.
If light water is used U235 is needed as water tend to absorb the neutrons. So uranium is enriched to 3 to 7%.
(instead of .75%).
If heavy water is used, natural uranium can be used are the neutron are not absorbed that much.
more about it
more about fission
here to learn more about it
source: http://www.sparknotes.com/math/precalc/conicsections/section1.rhtml