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110 Cards in this Set
- Front
- Back
- 3rd side (hint)
If you have a carbon-12, and a carbon-14 nucleus, both of which are isotopes, which one is more unstable and why? |
The carbon-14 nucleus will be more unstable because is has more neutrons, so it's more likely to decay. |
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How often does nuclei decay happen? |
Nuclei decay happens randomly. |
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What is the decay constant? What is the symbol for decay constant? What is the unit for decay constant? |
Decay constant - The probability of a nucleus decaying in the next second. Symbol is lambda. Unit is per second (s^-1 or /s) |
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When looking at one nucleus, would the decay constant be big or tiny and why? If you look at multiple nuclei, will the decay constant be larger or smaller than when looking at one nucleus? And why? |
The decay constant is usually 'tiny' if you are looking at one nucleus because it's very unlikely that the nucleus will decay in the next second. If you look at multiple nuclei, the decay constant will be larger than when looking at one nucleus because the chances of one of them decaying in the next second will be greater (lambda↑) |
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If we have a lump of undecayed radioactive material at the start, we can say none of the nuclei in that lump of material have decayed yet. When the material starts to decay, what assumption can we make about the number of decays per second? What does this imply about the radioactivity at the start? |
When the decay begins, we can assume that we will get many decays happening per second. This implies that there is high radioactivity at the start. (Many decays per second) |
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In nuclear physics, is activity and radioactivity interchangeable? |
Yes. They both mean the same thing in nuclear physics. |
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Define Activity/Radioactivity. What is the unit for this? |
Activity/Radioactivity - The amount of nuclei decays happening per second. Unit is c.p.s (counts per second) OR Bq (Bequerels). |
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After the lump of radioactive material has started to decay, and one half life passes, what 3 things change and what happens to these 3 things? |
After 1 half life passes; 1) Number of undecayed nuclei 2) Mass of undecayed material 3) Level of radioactivity All halve. |
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Define Half life. |
Half life - The time taken for the radioactivity of an isotope to halve. |
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Let's say we have all nuclei (represented by 1). How many half lives will it take for us to get to ⅛ of the nuclei? |
1→(1hl)→½→(1hl)→¼→(1hl)→⅛ 3 half lives to go from all nuclei (1) to ⅛ nuclei. |
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Half life can be represented on a graph. For this graph, the x-axis is days and the y-axis is activity (in c.p.s or Bq) 1) What can the variable on the x-axis be replaced with? Why? 2) What can the variable of the y-axis be replaced with? Why? |
1) x-axis can be replaced with months, years, secs etc (any frame of time since half life can be any frame of time) 2) y-axis can be replaced with mass of undecayed nuclei or number of undecayed nuclei because both of those also halve when 1 half life passes. |
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What kind of decay do half life graphs show? |
Half life graphs show exponential decay.
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From this graph, what is the half life? Why? |
The half life is 1.5 days since it takes 1.5 days for activity to halve. |
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Sometimes no graph will be given to you and you'll be expected to find half life.
Practice: Radioactivity 2000Bq→250Bq in 6 days. Find half life.
HINT: TRY TO FIND NO° OF HALF LIVES FIRST. |
2000→(1hl)→1000→(1hl)→500→(1hl)→250
3 half lives.
Total time / no° of half lives = half life. 6 days ÷ 3 = 2 days.
2 days = 1 half life. |
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Practice 2: 1 half life is 10 hours. What would the activity be after 40 hours if it started at 145 c.p.s, and 25 c.p.s of that reading is a Background Count?
Also: What is a background count? Give 2 possible sources of a background count. What should we do with background count if it's given to us? |
NOTE: Background Count is when you also measure radiation from other sources as well. E.g. Cosmic rays, radon gas etc.
Whenever you're given a background count, subtract it from the recorded count to get the actual count.
145 - 25 = 120 c.p.s
Half life no°: 40/10 = 4 half lives
120→(1hl)→60→(1hl)→30→(1hl)→15→(1hl)→7.5
New activity = 7.5 c.p.s |
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What is background count? Give two examples of sources of background counts.
If you're given a background count and a recorded count, what must you do to get the actual count? |
Background Count is when you also measure radiation from other sources as well. E.g. Cosmic rays, radon gas etc.Whenever you're given a background count, subtract it from the recorded count to get the actual count. |
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What 3 symbols do I need to know? (isotope activity, no of undecayed nuclei, decay constant) and their units. |
A: activity of an isotope (c.p.s or Bq)
(Lambda): decay constant (/s or s^-1)
N: No° of undecayed nuclei (no unit) |
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What does the activity of a radioactive sample depend on? What proportionality can we create from this piece of information? Why is this proportionality valid? What equation is This proportionality represented by? |
It depends on how big it is (how many nuclei are in it). We can say A oc N since the more nuclei we have, the higher the activity. This proportionality is represented by the equation (see picture) |
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The equation for nuclear activity can have a minus in it, but does it have to have a minus? Why is the minus there? |
The minus doesnt have to be there. The minus is there to show that each decay reduces the no° of nuclei. |
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There is another important equation I need to know. What is it? (It's a fraction of ... Left.) (There is a derivation for this equation, but I don't need to know it)
State what each part of the equation means, and its units. |
Its a fraction of mass/activity/number of nuclei left. (Essentially, it's the fraction of original left).
A↓0, m↓0, N↓0 - original activity/mass/number of nuclei at start.
(Lambda) is decay constant
t is the time that has passed. |
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Using this equation, derive the equation for half life. (Let 1 half life = t↓½) |
When 1 half life passes, fraction of original = ½
Ln both sides. |
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There are 2 important times I need to know about when looking at decay. One of them is half life (t↓½). What is the other important time? What is the symbol for this time? |
Time constant (t↓c) |
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Define time constant. |
Time constant (t↓c) - The time at which (See picture)
OR
The time at which the fraction of (original) remaining = 0.37. E.g. N / N↓0 = 0.37 |
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Derive the equation for time constant using eqn in picture. |
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When time = t↓c, what is N / N↓0 equal to? |
N / N↓0 = 0.37 |
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Let's say we have a source of gamma radiation (which is nuclei decaying by releasing energy, NOT changing themselves in this case),
Explain, with steps, how you will measure the number of decays happening per second. |
1) Keep the source in an enclosed area (preferably a sphere)
2) Connect a GM (Geiger Muller) counter to where the source is
3) The GM counter will record the no° of decays happening per second (in c.p.s or Bq).
4) The area of the detector only covers a small part of the imaginary sphere, so:
Measured rate from GM / total activity = Area of GM counter / Area of container ( 4{pi}r² here ) (this eqn also shown on hint sheet)
Then solve for total activity (number of decays happening per sec) |
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For beta decay, can the GM counter method be used to calculate activity?
Why would the value for beta activity be less accurate than the value for gamma activity? |
The GM method can be used for beta decay, but
The value for beta activity will be less accurate because beta radiation is reduced by air, and alot less of the beta radiation will be recorded. |
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For alpha decay, can the GM method be used to calculate activity? Under what circumstance can the GM method be used to calculate activity in alpha decay? |
The GM method can't be used to calculate alpha decay activity at all (UNLESS IN A VACUUM) |
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For a gamma radiation source, If we have 2 circles, one with a smaller radius (r↓1) and another with a bigger radius (r↓2), the radiation will pass through both spheres. But what will be different at the spheres, and at which sphere would it be less? |
The intensity of the radiation for every m² will be different at each sphere. The intensity of the radiation for every m² at the bigger sphere will be less than the intensity of the radiation for every m² at the smaller sphere. |
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What is the equation for the intensity (I) of a radioactive source, if the source was contained in a sphere? State what each part of the equation means. |
Intensity symbol is I k is a constant
4(pi)r² is surface area of a sphere |
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From this equation, what 2 things are constant? (assuming radioactive source stays the same)
Using this information, what proportionality can we create?
And what equation can we create for 2 different distances from the radioactive source? (NOTE: The equation you create is the equation for inverse square law). |
I oc 1 / r²
Equation created: Intensity↓1 x {dist↓1}² = Intensity↓2 x {dist↓2}²
For 2 different distances from the radioactive source. |
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Proportionality Practice: If we move the GM counter x2 distance away, what happens to intensity? |
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Practice Question: What happens to intensity if you move 2m further away? (Assume you know intensity 1, and original distance from source) |
You can do I2 / I1 to see how much bigger/smaller the new intensity is. |
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What is nuclear fission? Where is nuclear fission used (2 things)? What kind of nuclei does nuclear fission usually occur in? |
The process of breaking nuclei apart. Nuclear fission is used in nuclear power stations and atomic bombs. Nuclear fission usually occurs in heavy (larger) nuclei. |
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Name 1 nucleus that nuclear fission occurs in. |
Uranium-238 |
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Is uranium-238 stable or unstable? Why? |
Uranium-238 is fairly unstable because it has more neutrons than usual, meaning it's ready to break apart. |
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Uranium-238 is unstable and ready to undergo nuclear fission, but what is done to give it a little extra jumpstart to break apart? Why do we do this? |
We fire 1 neutron into it to make it unstable enough to break apart. |
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Describe the process of nuclear fission using uranium-238. Draw a diagram as well, labelling any parts of relevance. Give the steps as well. |
1) 1 neutron is fired into an unstable uranium-238 nucleus, making it unstable enough to break apart. 2) The uranium-238 splits into 2 smaller nuclei (known as daughter particles), AND 2 or 3 neutrons are also emitted in the process. 3) If there are other uranium-238 nuclei around, the emitted neutrons will then cause fission to occur in those nuclei, leading to a chain reaction. |
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Nuclear fission can lead to chain reactions. Chain reactions can be a good thing if they're controlled, but can be a VERY BAD thing if it's left unchecked. What is the reason for this? |
This is because every time fission happens, energy is released from the nucleus. |
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Nuclear fission is used in nuclear power stations. What is the energy produced from nuclear fission used for in power stations? (After the energy is used, explain what happens in a nuclear power station). |
In a nuclear power station, the energy produced from nuclear fission is used to heat water to make steam, to turn the turbine, which powers the generator, which generates electricity, which goes to transformers to produce the correct voltage, which then gets transferred to homes. |
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Nuclear power stations use nuclear reactors to do nuclear fission.
Draw what a nuclear reactor looks like, and label every part of importance. |
Control rods can be made od Boron or Cadmium. |
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In a nuclear reactor, we have some liquid known as the coolant or special coolant (NOT the water that gets turned into steam). What is the purpose of the coolant in a nuclear reactor? |
The coolant takes the heat from the energy to the water, which then turns the water to steam. |
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In a nuclear reactor, fuel rods are put into the coolant. 1) What do the fuel rods contain? 2) What occurs inside the fuel rods? 3) What will this cause to happen? |
1) The fuel rods contain pelletd of refined Uranium-238. 2) Fission will occur inside the rods. 3) This will cause neutrons to fly back and forth, from rod to rod, causing fission to occur in the next rod, therefore heating the coolant up. |
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If you just had the fuel rods with neutrons going back and forth (with no moderator), would fission occur?
Why? |
If you just had the fuel rods with neutrons going back and forth, you would get little or no fission because the neutrons are travelling too fast (with too much energy) to be absorbed by any uranium-238 nuclei. |
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Where are moderators placed in a nuclear reactor?
What is the purpose of moderators in a nuclear reactor? What can moderators be made out of? |
Moderators are placed inbetween each fuel rod.
Moderators are used to slow the neutrons down so they can be absorbed.
Moderators can be made out of water or graphite. |
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Does the use of moderators increase or decrease the rate of nuclear fission?
Why? |
The use of moderators increases the rate of nuclear fission because by slowing down the neutrons, it allows for more of them to be absorbed, increasing the amount of fission that can take place.
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In a nuclear reactor, where do we put control rods? What are the control rods used for? |
Control rods are put between the fuel rods. Control rods are used to absorb neutrons, so they don't make it to the next fuel rod to cause fission. |
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If there is too much fission occuring in a nuclear reactor, what do we do with the control rods? Why? If we want more fission, what do we do with the control rods? Why? |
If there is too much fission occuring, we drop the control rods in-between the fuel rods so that they can absorb the neutrons. If we want more fission, then we can lift the control rods back up, so more fission can happen since more neutrons can travel between the fuel rods. |
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What are the 2 substances that control rods are usually made out of? |
Control rods are usually made out of Boron or Cadmium. |
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What is one of the problems with nuclear reactors? (Has to do with the fuel rods) |
One problem with nuclear reactors is that the number of uranium in the fuel rods will actually decrease overtime, and we can't keep the reactor going until there's no uranium left. In fact, fuel rods are used up when there's still quite alot of uranium left in them that haven't fissioned. |
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When a fuel rod has been used up, it must be disposed of, along with the remaining uranium (that is still radioactive) inside it. Explain how the fuel rods are disposed of. |
The used up fuel rods (along with their casings) are put in acid to melt them, making a very harmful nuclear waste. The waste is then vitrified (encased in glass) because glass is non-porous (liquids can't seap through or come out of it). The vitrified waste is then buried underground. |
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The nuclear waste produced when melting used up fuel rods is very harmful. What will a few ml of this waste do to a reservoir of water? |
A few ml of this nuclear waste in a reservoir of water will make the water unsafe to drink. |
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Where must nuclear reactors be kept, relative to people? |
Nuclear reactors must be kept as far away from people as possible. |
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Where would be a good place to put nuclear reactors?
What is the problem with putting nuclear reactors here?
How is this problem tackled? Why does this solution resolve the problem? |
Burying nuclear reactors underground may be a good idea.
The problem with putting nuclear reactors underground is that when disposing of used up fuel rods, the melted fuel rods could get into water supplies.
This problem is tackled by vitrifying the waste (encasing it in glass) and burying it further underground. This solution resolves the problem because glass is non-porous (liquids can't seap through or come out of it), so no waste can contaminate water reservoirs. |
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What is Nuclear Fusion? In what kind of nuclei does nuclear fission usually happen to? Where does nuclear fusion usually happen (2 things)? |
Nuclear Fusion - The process of fusing nuclei together. Fusion usually happens to light (smaller) nuclei. Nuclear fusion usually happens in the sun and in hydrogen bombs (a type of nuclear bomb.) |
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Write down the nuclear reaction for two Deuterium nuclei (hydrogen nuclei, but with 1 extra neutron. Basically mass number, 2, atomic number, 1) undergoing fusion together.
Write down the result, the condition needed for this nuclear fusion to happen, and what is given off as a result of the reaction. |
They add, making a helium nucleus. Energy is given off as a result. |
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How many hydrogen nuclei are there in the sun (in general)? What kind of hydrogen nuclei are in the sun? |
Loads! Normal hydrogen and hydrogen isotopes are in the sun (Deuterium, which is 1 neutron 1 proton, and Tritium, which is 2 neutrons and 1 proton). |
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When we have hydrogen nuclei in normal conditions, will they fuse together? What would happen if they fused together in normal conditions? Why don't hydrogen nuclei fuse together in normal conditions? |
In normal conditions, hydrogen atoms won't fuse together. If they did fuse together in normal conditions, we would have hydrogen bombs happening naturally. Hydrogen nuclei don't fuse together in normal conditions because hydrogen nuclei are positively charged (just like any other nuclei.) And like charges repell. For nuclear fusion to happen, the nuclei must get VERY CLOSE to each other (about 5fm), and they can't get that close normally. |
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What conditions are needed for nuclear fusion to happen? Explain why each condition is needed. (4 conditions)
What will happen if these 4 conditions are met? (Use 2 normal hydrogens to explain) |
1) The 2 nuclei must approach each other VERY QUICKLY so they can get very close to each other and overcome the electrostatic repulsion.
2) Lots of energy is required and must be available so the nuclei will have more speed when approaching each other.
3) The 2 nuclei must get very close to each other (about 5fm) so the strong nuclear force can take over.
4) You can't let any of the particles undergoing nuclear fusion touch anything because they will lose alot of their energy if they do touch something. If these conditions are met, the hydrogen nuclei will fuse together, causing their protons and neutrons to add (Basically, their mass and atomic numbers will add). |
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When nuclear fusion occurs, what is given out?
In what process is the same thing given out? |
Energy is given out.
Energy is also given out in nuclear fission. |
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Nuclear fusion happens alot in the sun. Why? |
Nuclear fusion happens alot in the sun because the temperature in he sun is EXTREMELY HOT!!!, meaning that every particle is moving very fast, including the hydrogen nuclei, so the hydrogen nuclei can fuse together. |
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Scientists have tried to make a nuclear reactor using fusion, but have struggled. Why? |
They have struggled because you can't let any of the particles involved in the process touch anything. As soon as they touch something, they lose alot of their energy, meaning they won't be moving fast enough to fuse. |
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How have scientists tried to create a nuclear reactor using fusion? (2 things)
What problem arose when they tried to make a nuclear fusion reactor? |
They have tried to levitate the particles undergoing fusion in a ring using magnets (to stop them from touching anything so they don't lose their energy).
They have also tried to make the conditions hot enough so the particles fuse together.
The problem was that you can't get a chain reaction from nuclear fusion very easily. Alot of fusion must be happening at one time for a chain reaction to occur. It's difficult to artificially get enough energy out of each fusion, in a reactor, to cause another fusion. |
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Does alot of nuclear fusion happen in the sun? Do nuclear fusion chain reactions happen in the sun? |
Yes. Yes. |
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Which is easier to create a chain reaction with? Nuclear fusion or nuclear fission? |
Nuclear fission. |
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Briefly explain how a chain reaction is caused in nuclear fission. |
One neutron goes into an unstable nuclei, The nuclei splits apart, 2 or 3 neutrons come out, Those neutrons go and cause nuclear fission, And a chain reaction begins. |
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When referring to the mass of an atom or a nucleus, do we refer to them in relative numbers or kg? Can we refer to them in both? |
When referring to the mass of an atom or a nucleus, we usually refer to them in relative numbers and not kg. We can refer to them in both relative numbers AND kg though. (Depending on what the question requires.) |
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Let's say we have a standard helium atom. What is the mass number? |
The mass number is 4. |
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Usually, relative atomic mass doesn't have a unit. In reality, does it have a unit? If so, what is the unit for mass number (relative atomic mass)? What is the unit for any nucleon (proton or neutron)? |
In reality, relative atomic mass DOES HAVE A UNIT! The unit for relative atomic mass is 'u' The unit for any nucleon is 'u' |
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What is 1u equal to? What is the reason for this? (What is relative atomic mass actually based off? Why is 1u equal to what it's equal to?) |
1u = 1/12 the mass of a carbon-12 atom. The reason for this is because mass number (or relative atomic mass) is actually based off carbon-12. Carbon-12 has 6 protons and 6 neutrons, thus 12 nucleons. So 1u must be 1/12 the mass of a carbon-12 atom since 1/12 the mass of a carbon-12 atom is the mass of 1 nucleon. 12 x 1/12 = 1 |
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In units of u, what would you expect the mass of 1 neutron and 1 proton to be? Are these the correct masses of 1 proton and 1 neutron in terms of u? |
We would expect: 1 proton = 1u 1 neutron = 1u These masses in terms of u are NOT CORRECT! |
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In reality, when measured to a high degree of accuracy, what is the accurate mass in units u for;
A proton
A neutron
An electron? |
⚫ proton: 1.007276 u ⚪ Neutron: 1.008665 u . Electron: 0.000549 u |
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In nuclear physics, do we use the general, expected masses (proton = 1u and neutron = 1u) or the very accurate masses? Why? |
In nuclear physics, the more accurate proton and neutron masses must be used because the very small mass difference between the expected mass and the actual mass makes all the difference. |
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Let's say we have a normal helium atom (2 protons, 2 neutrons, 2 electrons). 1) Using the accurate masses of the constituents, calculate the mass that you would expect the helium atom to be. When the helium atom's mass is measured to a high degree of accuracy, we find it to be: m = 4.002603 u. The calculated mass and the measured mass are different. 2) What do we call the difference between the calculated mass (mass from adding the constituents) and the measured mass? 3) What is the equation used to find 'this thing'? And what is the symbol for this thing? 4) Calculate this thing for a helium atom using the calculated helium mass and the measured helium mass. |
1) m = 2(1.007276) + 2(1.008665) + 2(0.000549) = 4.032980 u 2) The difference between the calculated mass (mass from adding the constituents) and the measured mass is called the mass defect. 3) mass defect equation: Mass of constituents - actual mass = mass defect. (∆m) 4) mass defect for a helium atom: 4.032980 u - 4.002603 u = 0.030377 u |
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Which is ALWAYS BIGGER? Mass of constituents (calculated mass) or actual mass (mass when in nucleus)? |
Mass of constituents > actual mass ALWAYS. |
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If we take protons, neutrons and electrons and shove them together to make an atom, What is lost in the process and what is it lost as? |
Mass is lost in the process as ENEEGY! |
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There are 2 different methods to calculate how much energy the mass defect is lost as in joules.
1) Describe how you would do the the 1st method.
2) Describe how you would do the 2nd method.
3) Which method is better/quicker and should be used more? |
1) a) Convert the mass defect from 'u' to kg by multiplying by (1.67 x 10^-27)
b) Sub the mass defect in kg into: E = ∆mc² where ∆m is the mass defect and c is speed of light. DONE!
2) a) You can go straight from 'u' to MeV (Mega electron-volts) by multiplying the mass defect in 'u' by x 931.3.
b) You can convert MeV to J (joules) by multiplying by x (1.6 x 10^-13) since 1 MeV = (1.6 x 10^-13) J using conversions from AS + standard unit conversions. (M = x 10^6)
3) Method 2) is the quicker method, and should be used more. |
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If 1u was turned into energy, how much would the energy be in MeV? |
The energy would be 931.3 MeV. |
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What is the amount of energy that the mass defect is lost as called? |
Binding energy. |
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Define Binding Energy. |
Binding energy - the energy (or work) required to separate a nucleus/atom into it's constituents. |
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The energy that the mass defect is lost as when the constituents come together to form an atom or nucleus is the same as... (What?) What are both of these energies equal to? |
The energy needed to separate out an atom or nucleus into it's constituents to regain the mass defect as mass. Both of these energies are equal to the Binding Energy. |
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We discovered the mass defect of a helium atom to be 0.030377 u from before. Find the binding energy of a helium atom. |
Mass defect x 931.3 = binding energy in MeV. x (1.6 x 10^-13) = binding energy in joules. 0.030377 x 931.3 = 28.3 MeV 28.3 x (1.6 x 10^-13) = 4.528 x 10^-12 J |
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Any alpha particle that didn't hit the nucleus in the middle did what? Where there alot of alpha particles that did this? |
Any alpha particle that didn't hit the nucleus just went straight through the thin gold foil (transmitted through the thin gold foil). There were alot of alpha particles that did this. Most of the alpha particles were transmitted through the metal gold foil. |
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Define Distance of closest approach. |
Distance of closest approach - How close an alpha particle (or any other +ve particle) can get to a nucleus. |
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How would you calculate the distance of closest approach for a positive incident particle being fired at the nucleus of an atom?
Give the steps. |
1) Calculate the kinetic energy of the +ve incident particle (e.g. alpha particle) using Ek = ½mv²
2) Calculate the potential energy between the incident particle and the nucleus where their centres are separated by a distance 'r' using:
Ep = (kQq)/r
Where k = constant (9 x 10^9. Must remember) Q = charge of nucleus q = charge of +ve incident particle r = distance between the two of their centres (dist of closest approach in this case)
3) Equate the Ek and Ep to each other. Ek = ½mv² Ep = (kQq)/r ½mv² = (kQq)/r
4) solve for 'r'. r is the distance of closest approach. r = (kQq) / (½mv²).DONE! . DONE!
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Since Rutherford's experiment was done, what have we found out about the nucleus? |
Since Rutherford's experiment, we've found out that the nucleus isn't just a positive lump, but is actually a particle made up of protons and neutrons. |
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When referring to the size or mass of a nucleus, we are only concerned with what characteristic of the nucleus? Why? |
When referring to the size or mass of a nucleus, we are only concerned with the mass number because both protons and neutrons are included in that. |
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What is the mass number and atomic number of an alpha particle (helium nucleus)? |
Mass number - 4 Atomic number - 2 |
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Write the general symbol notation for any atom. Give the CORRECT SYMBOLS as well. Label what each part represents. (Important for later eqns) |
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We can calculate the radius of a nucleus. Draw a helium nucleus and label the nuclear radius. |
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The next few flashcards will address how to calculate nuclear radius.
What shape are nuclei generally? What 2 proportionalities can we create based on this fact? (Find the 1st proportionality, then manipulate it to get the 2nd proportionality) |
Nuclei are generally spherical, so we can make these proportionalities:
A οc R³ (No° of nucleons are proportional to R³)
And putting the proportionality the other way around gives:
R oc A^⅓ (R is proportional to the cube root of the no° of nucleons) NOTE: R is nuclear radius, and A is the number of nucleons (mass number) |
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Even though you always have to put in energy to separate nuclei (Fission by firing high energy, high speed neutron into nucleus) or fuse nuclei (Fusion by firing high speed, high energy nuclei in to each other),
We still manage to get energy OUT of nuclear fission and fusion. What concept explains why this is possible? |
The TOTAL BINDING ENERGY (what's going into a nuclear reaction, and what's coming out) is the concept that explains how we get energy out of fusion and fission. |
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(Basis for Explanation on how we get energy out of fission): Let's say we have uranium-238. It has a certain binding energy.
When uranium-238 is fissioned by firing a neutron into it, what is released? Draw a diagram to show this. Label the 'before' and 'after' states.
In this process, what will happen to the total binding energy? Explain why. |
2 daughter particles and 2 or 3 neutrons are released. Energy is also released. (Mass defect is released as energy)
In this process, the total binding energy will increase because:
energy is given out in the first fission. Neutrons are released, and they go on to do more fission, causing even more energy to be given out than initially, causing the total binding energy to increase overtime. |
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(Basis for Explanation on how we get energy out of fusion):
Let's say we have 2 deuteriums (hydrogen isotopes, mass number 2, atomic number 1).
If we fuse them together, what will they make?
What is given out in the process and as what?
What happens to total binding energy? |
They make helium.
The mass defect is given out as energy.
The total binding energy increases. |
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This flashcard will partially explain how we get energy out of fission.
Fission can be done with uranium-238.
Give one characteristic of uranium-238.
If nuclei have this characteristic, what will they release more of when they are fissioned?
If you try to fuse 2 nuclei with this characteristic, what problem will arise? |
Uranium-238 is a very heavy nucleus.
If nuclei are heavier, they will release more energy when they are fissioned.
If you try and fuse 2 heavy nuclei together, the problem is that you will need to put more energy in to begin with than you are getting out. |
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This flashcard will partially explain how we get energy out of fusion. What is the main characteristic of nuclei that undergo fusion? If nuclei have this characteristic when undergoing fusion, what happens to the amount of energy released from the fusion? If you try to fission nuclei with this characteristic, what problem will arise? |
Nuclei that undergo fusion are usually light. If light nuclei undergo fusion, they release lots of energy when they're fused together. If you try to fission light nuclei, the problem is that you will have to put in more energy than you are getting out. |
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In both fission and fusion, if the 'total binding energy' has increased, the products are more... (What?) |
The products are more stable. |
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'Binding energy per nucleon' is also important. Define Binding energy per nucleon. |
Binding energy per nucleon - The binding energy of a nucleus divided by the number of nucleons in it. |
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There is a graph that shows how the binding energy per nucleon changes as the number of nucleons in a nucleus increases. Draw what this graph looks like. Label the x-axis and y-axis correctly. Label any point of importance. Label the area where fission will occur and where fusion will occur. |
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On this graph, before helium, as the number of nucleons in a nucleus rise, Binding energy per nucleon rises. When is the maximum binding energy acheived? Which atom is the atom with the highest binding energy? |
Maximum binding energy is acheived when there are 56 nucleons (Fe or Iron nucleus) Atom with the highest binding energy per nucleon is Iron (Fe) |
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As stated before, something that has a higher binding energy per nucleon is more stable.
Using this information, explain why nuclei that are lighter than iron-56 tend to fuse
and
nuclei heavier than iron-56 tend to fission. |
Nuclei that are lighter than iron-56 fuse together so they can go towards iron-56, because that means that their binding energy per nucleon is increasing due to their nucleon number increasing, making them more stable.
Nuclei that are heavier than iron-56 tend to fission so they can go towards iron-56, because that means that their binding energy per nucleon is increasing due to their nucleon number decreasing, making them more stable. |
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Summary: Nuclei to the left of iron do what? Nuclei to the right of iron do what? |
Nuclei to the left of iron fuse Nuclei to the right of iron fission. |
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On the binding energy graph, there is a bump on the graph (see where the arrow is pointing. First bump of graph). What nucleus is located at this bump? What 2 characteristics does this nucleus have that is unusual? What do these characteristics explain and how? |
Helium nucleus is located at this bump. Helium has an unusually high binding energy per nucleon, meaning that it's unusually stable for a smaller nucleus/atom compared to it's immediate neighbours. These characteristics explain why when we have unstable nuclei, quite often they emit alpha radiation. They emit a helium nucleus because that's a very stable particle with a high binding energy to give out. |
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Ernest Rutherford was the creator of the Rutherford Scattering.
He was the first person to prove what? (2 things)
What was the name of the experiment that he used to do this? |
He was the first person to theorize and prove that atoms aren't actually a plum pudding (which was the accepted model for an atom some time in the past), So atoms aren't just a solid sphere with electrons stuck on the outside.
He was also the first person to prove that most of an atom is actually empty space.
He did this using what we now know as the 'Rutherford Scattering'. |
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Briefly explain how the Rutherford scattering was done. Draw a diagram to show what was done. Label any part of the diagram that aids in the explanation on how the Rutherford Scattering was done. What did Rutherford find? (What did he see happen)? (2 different observations) What did each observation prove? What did Rutherford assume about the nucleus? |
What Rutherford did was fire alpha particles at this metal foil/leaf (which was thin gold foil in AS particles?) Observation 1: He found that most of the alpha particles went straight through the leaf (they were transmitted through the leaf.) This proved that the majority of an atom's volume is just empty space. Observation 2: He found that some alpha particles (about 1/10000) were being deflected over 90°. (Basically, they were coming back on themselves). This proved that there must be a specific positive part of an atom, but it must also be very small (The nucleus) if it only deflects 1/10000 alpha particles back. Rutherford assumed that this positive part (nucleus) was in the middle of the atom and was very small.
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Rutherford calculated that the amount of alpha particles being deflected back over 90° was about 1/10000.
Explain how he calculated this. |
He modelled the atoms that the alpha particles were incident on as a circular target. (Model on hint sheet.)
If the diameter of the whole atom = D And the diameter of the nucleus = d, (See image for equation on how he got to 1/10000).
So if alpha particles were fired at the circular target atom, then about 1/10000 of the alpha particles would be deflected over 90°. |
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Rutherford calculated that the amount of alpha particles being deflected back over 90° was about 1/10000. What does this suggest about the size of the target (nucleus) compared to the size of the atom? |
This suggests that the size of the target (nucleus) is about 1/10000 the size of the whole atom. |
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In the last flashcard, we found the proportionality: R oc A^⅓. What is the equation that represents this proportionality? State what each part of the equation means. |
R = nuclear radius r↓ = constant in eqn sheet A = no° of nucleons in the nucleus (mass no°) |
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If you are comparing 2 different nuclei, what will always be the same? If you are comparing 2 different nuclei, and one of the variables are unknown, explain how you can find this missing variable using the thing that will always be the same. |
The constant r↓0 will ALWAYS BE THE SAME! (After doing the steps in the image, you can then solve for any required unknowns.) |
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How the nuclear radius varies with the number of nucleons in a nucleus (R = r↓0 x A^⅓) can be shown on 2 different graphs.
Derive the equation for each graph (if necessary), label the x and y axis correctly, label the y intercept correctly (if necessary), and label what the gradient is. |
Use folder to look at graphs if the picture is too blurry. |
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