Where did the energy for this come from? The nucleus.

Compare the 2 forces: electromagnetic: Fe = Is a force between two ___________________. Attracts ________________ and repels _____________ ___________________  ________range Binds the ____ to the ___ within an atom and bonds_____________ to other ____________ kq1q2/r2 charges opposite q's like q's inverse square ∞ e- p atoms atoms 2. strong nuclear: Fsn Is a force between two _________________ Always________________, even between_____________ _______________ force, but very ______________range Holds the ____________________together masses attractive protons Strongest short nucleus

n =_____________ neutron Ex: In a ____________ nucleus (___________): small helium p =___________ proton A close up of the 2 p: Fe Fsn Fe Fsn Fsn ________________ > Fe ___________________ The _________________ wins  _____________nucleus attraction repulsion attraction stable In addition, the ________________are also attracted to the _______________ and to ________________ by the Fsn, and they have ________ Fe repulsion. neutrons protons each other no

Ex: In a ____________ nucleus (___________): large uranium 2 1 A close up of protons 1 and 2: Fe Fe Fsn 1 2 Fsn The _______________ Fe is ______ the Fe in small nuclei. BUT ______________Fsn is _____ the Fsn in small nuclei. repulsive < attractive <<< Repulsion ____________wins  nucleus __________ and _________ unstable decays. For bigger nuclei: # of n _____ # of p. Why? The n’s provide extra Fsn _____________w/o Fe ___________. > repulsion attraction

The existence of the ______________force means that there is an energy _____________ the nucleus called the _______________ energy. __________________discovered that this energy results in nuclei having more ____________ : nuclear within bonding Einstein mass Equivalence The _______________________ of Mass and Energy Ex. If 5.0 x 10-3 kg of mass is totally converted to energy, how much energy will result?

The existence of the ______________force means that there is an energy _____________ the nucleus called the _______________ energy. __________________discovered that this energy results in nuclei having more ____________ : nuclear within bonding Einstein mass Equivalence The _______________________ of Mass and Energy E = mc2 Ex. If 5.0 x 10-3 kg of mass is totally converted to energy, how much energy will result? E = mc2 (5.0 x 10-3 kg) E = (3.00 x 108 m/s)2 Or joules E = 4.5 x 1014 kg·m2/s2

Notes: If any object with ____________is converted completely into pure ____________ , it will release a total of ________ joules. Think of mass as _________________ energy. 2. The term _______ is simply a ______________________ between mass m and energy E. The mass is not moving at the ________________________ ! What will the graph shown at right look like? What quantity does the slope represent? mass m energy mc2 "congealed" c2 conversion factor speed of light E m c2

splitting __________ nuclei into______________ ones Ex 1: ____________ splitting __________ nuclei into______________ ones used in __________________________ fission bigger smaller nuclear reactors before: after: n Ba-142 n U-235 n Kr-91 n n10 + U23592 Ba14256 + Kr9136 + 3n10 mass: 1 + 235 = 142 + 91 + 3(1) charge: 0 +92 = 56 + 36 + 3(0)

Is charge conserved? Yes. Is mass conserved? YES: The # of nucleons (n and p) is __________________. NO: The nucleons in Ba and Kr are ________________!!! Yes and no. the same smaller n10 + U23592 Ba14256 + Kr9136 + 3n1o _________mass! more ____________mass! less The “missing” mass became _____________ ( E = mc2) in the form of _______ of Ba, Kr, n and _________________. This energy can be used 1/ _____________________________ in a ____________________ or 2/ ________________________ in an _______________________ . energy KE radiation to heat water to steam power plant to kill people atomic bomb

occurs when the neutrons produced in one reaction are used to start new reactions Chain reaction - _______________________________________ _______________________________________________________ U-235 n ________________– used to ____________the reaction by ____________neutrons control rods limit absorbing

First atomic bomb test: “Trinity” July 16, 1945, at Alamogordo, New Mexico was set off by imploding a subcritical mass of plutonium. 20 kilotons of TNT Today:

First military use of atomic weapons: Hiroshima, Japan, August 6, 1945.

It contained 64 kg of uranium, of which less than a kilogram Little Boy use U-235 H i r o s h m a It contained 64 kg of uranium, of which less than a kilogram underwent nuclear fission, and of this mass only 0.6 g was transformed into energy

Nagasaki – 3 days later Replica of Fat Man: Method: implosion of Pu Yield: 21 kilotons of TNT

New York Nuclear Power Plants: Indian Point: 1970 MW Nine Mile Point: 1756 MW 2 plants in Oswego

James Fitzpatrick: 844 MW near Oswego R. E. Ginna: 498 MW on Lake Ontario east of Rochester

 combining ____________nuclei into _____________ ones Fusion Ex 2: _____________:  combining ____________nuclei into _____________ ones  powers _________________ and__________________ smaller bigger the stars the Sun before: after: H-2 He-3 n H-2 H21 + H21 He32 + n10 mass 2 + 2 = 3 + 1 charge 1 + 1 = 2 + 0

Is charge conserved? Yes. Is mass conserved? YES: The # of nucleons (n and p) is __________________. NO: The nucleons in He32 and n10 are ________________!!! Yes and no. the same smaller H21 + H21 He32 + n10 _________mass! more ____________mass! less The “missing” mass became _____________ ( E = mc2) in the form of _______ of He and n and _________________. The # of fusion power plants = ____ because it is difficult to get the _______________ close enough so that the _________________ attraction > electric _________________ . energy KE radiation + nucleons strong nuclear repulsion

Fission: How can both fission and fusion release energy? Both result in less mass. Fission: Big nuclei can be fissioned to produce energy b/c the products have less mass.

Fusion: Small nuclei can be fusioned to produce energy b/c the products have less mass. Notice: In both fission and fusion, iron (Fe) is the lowest point on the curve. Its nucleons are smallest.

Number of fission reactors in the world: Number of fusion reactors in the world: 439 reactors in 31 countries 150 naval vessels 6% of world’s energy 15% of world's electricity In the US: 10% of fission energy is supplied by using old Soviet warheads.

g _________ production: a gamma ray _____________ gets “tickled” as it passes a nucleus. Its ____________ becomes a _____________ and _________________ pair Pair photon energy matter antimatter before: after: g-ray e- e+ nucleus nucleus g e- + e+ The nucleus acts like a _________________ . catalyst The e+ is a _______________: the antiparticle of the e-  same ____________ as the e-  opposite ____________of the e- positron mass charge

a. Compare the charge q before and after: = -1 + + 1 is conserved  charge _______________________ . b. Compare the mass before and after: = me- + me+ = 2me-  mass _______________________ . is not conserved c. Compare "mass-energy" before and after: Eph = me-c2 + me+c2 mass-energy _______________________ as long as Eph has an energy at least equal to _________________ is conserved (2me-)c2

Ex. Calculate the energy of the photon that is needed to produce an electron and positron pair. E = mc2 = 2mec2 = 2 (9.11 x 10-31 kg)(3.0 x 108 m/s)2 = 1.64 x 10-13 J What is the frequency of the photon? Eph = hf 1.64 x 10-13 J = (6.63 x 10-34 J s) f f = 2.47 x 1020 Hz

________________________ is ALWAYS conserved, even when _______________ is not. This is because mass can be converted to ________________ and vice versa, but neither __________nor ____________ can be destroyed. Mass-energy mass energy mass energy Ex: Is momentum p conserved? before: after: pe- pph pe+ Rewrite these as: = Momentum p is _____________________________ . always conserved.

g ? Ex: Could a g-ray produce two electrons? e- + e- charge: = -1 + = -1 + - 1  _________________ b/c charge _____________conserved. Impossible must be In sum: Momentum is _____________________ conserved. Charge is _________________________ conserved. Mass is ___________________________ conserved. Energy is _________________________ conserved. Mass-energy is ____________________ conserved. Numbers ___ and ___ are ___________ conserved when _______________ objects are involved. always always sometimes sometimes always 3 4 often bigger

2g Pair ______________________: matter and antimatter combine to form pure _________________ (photons). annihilation energy after: before: e- g rays e+ 2g e- + e+ a. Compare the charge q before and after: -1 + + 1 = + is conserved  charge _______________________ .

b. Compare the mass before and after: me+ + me- = + 2me- = is not conserved  mass _______________________ . c. Compare "mass-energy" before and after: me-c2 me+c2 Eph Eph + = + 2me-c2 2Eph = mass-energy _______________________ as long as Eph has an energy at least equal to ____________ is conserved me-c2 Eph = me-c2 = (9.11 x 10-31 kg)(3.0 x 108 m/s)2 = 8.20 x 10-14 J