- Monday - last lesson, extra help rm 245
- Tuesday - Review
- Wednesday - Wellness
- Thursday - Guest speaker, extra help rm 146
- Friday - Review
- Monday, Dec. 1 Test
First we wrapped up our discussion of fission by discussing the pros and cons of nuclear power.
Advantages and disadvantages of nuclear power
Pros:
- does not produce CO2, clean
- produces large amount of energy for small amount of fuel (high energy density)
- large reserves of nuclear fuel
Cons:
- warms up nearby lakes
- spent fuel is still radioactive
- dangerous to mine
- waste material from mining
Then we discussed fusion
Fusion
Lighter elements fuse together to form heavier elements
The sun fuses 4 H —> He in what is called the proton-proton chain.
The best fusion reactor we have is the sun.
Hydrogen mass: 1.008 amu = 1.6738 e -27 kg
Helium mass: 4.002 amu = 6.6455 e -27 kg
The mass of 4 H does not add up to 1 He. This was called the “mass defect”.
The missing mass is converted into energy.
E = energy
m = mass
c = speed of light, 3.00 e 8 m/s
Ex) How much energy is produced from the “mass defect”?
The mass lost is given by:
m = 4m(Hydrogen) – m(He)
m = 4(1.6738 e -27 kg) – (6.6455 e -27 kg) = 4.97 e -29 kgThis missing mass is converted into energy
E = mc²
E = (4.97 e -29 kg)(3.00 e 8 m/s)² = 4.47 e -12 J
Remember that this is for the producing of ONE He nucleus.
Ex) How much energy is produced from fusing 4g of helium (about 1 mole)?
4 grams of He is about 1 mole, which is 6.02 e 23 He nuclei. So the total energy is this number times the result from above.
E(total) = E x 1 mole
E(total) = (4.47 e -12 J)(6.02 e 23) = 2.69 e 12 J
This is a massive amount of energy!
A small amount of mass can be converted into a large amount of energy.
If we can do this in a fusion reactor we can produce useful energy with the only fuel being hydrogen!
Watch this video:
Homework
Complete these handouts
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