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Fuel-Based Energy
 Chemical Energy
 Nuclear Energy
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Science of Energy 2
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Chemical Energy
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Chemical energy is the energy in the bonds of a molecule. Breaking, reorganizing,
reestablishing chemical bonds can generate or consume energy.
H2
H2
H2O
H2O
286,000 joules per mole
O2
Combustion (burning with oxygen) of hydrogen releases energy
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Burning 1 gallon of gasoline releases 132 Mega joules
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Ex: If gasoline is $4 per gallon what is the cost of 1 Mega joule of energy obtained from gasoline?
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Ex: How many moles of hydrogen gas provide 1 Mega joule of energy?
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It is 3.5 = 1,000,000/286,000 moles
Ex: What should the cost of 1 mole of hydrogen gas be so that energy obtained from gasoline and
hydrogen gas have the same cost per Mega joule?
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It is $ 0.03 = 4/132 per Mega joule
It is $ 0.03/3.5 per mole of hydrogen gas
Ex: What is the cost of 1 kg of hydrogen gas bought at the rate above?
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1 mole of hydrogen weighs 2 grams. 1 kg has 500 moles of hydrogen and costs $ 4.3 = 500(0.03/3.5).
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The cost of hydrogen gas produced through electrolysis powered by wind energy is $ 3.74-5.86 per kg.
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Burning $4 worth of methane gas bought at $4 per Mega BTU gives 1,052 Mega joules.
Burning 1 gallon of gasoline bought at $4 per gallon gives 132 Mega joules.
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– Methane (natural gas) 6-7 times cheaper than gasoline to obtain the same amount of energy!
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Each atom has a nucleus and negatively charged electrons rotating in an orbit above the nucleus.
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Electrons are much lighter than the nucleus.
The movement of electrons around nucleus is intuitive and has the astronomical analogy of movement of
satellites around a large mass of a planet or a star.
In the nucleus of an atom, positively charged protons reside together with neutral neutrons.
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Nuclear Energy: Nucleus and Isotopes
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Both protons and neutrons have significant masses with respect to an electron.
The number of neutrons in the nucleus can be altered to obtain different isotopes of the same atom.
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As a convention, a superscript on an element’s notation is the atomic mass (number of protons and nucleus) of
the element and the subscript is the number of protons.
𝐻11 is the hydrogen element with 1 proton, 0 neutron and 1 electron.
𝐻12 is the hydrogen element (deuterium) with 1 proton, 1 neutron and 1 electron.
𝐻13 is the hydrogen element (tritium) with 1 proton, 2 neutron and 1 electron.
Hydrogen isotope 𝐻11
1 proton
0 neutron
Beryllium isotope 𝐵𝑒49
4 protons
5 neutrons
Deuterium isotope 𝐻12
1 proton
1 neutron
Tritium isotope 𝐻13
1 proton
2 neutrons
Beryllium isotope 𝐵𝑒411
4 protons
7 neutrons
~ 10-15
metres
Extra increase the volume and weight of a nucleus ⟹ Physical properties of isotopes are different.
neutrons do not change the number of electrons ⟹ Chemical (bonding) properties of isotopes are the same.
This mass to energy conversion is not explainable by standard Newtonian mechanics. Instead quantum
mechanics is employed to study the force/energy in the nucleus, which is extremely small.
Mass deficit is the source of nuclear energy, which must be
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Theoretical mass prediction=Number of protons * Mass of a proton + Number of neutrons * Mass of a neutron
Mass deficit = Theoretical mass prediction – Experimentally measured mass
Mass is turned into energy: 1 unit of mass gives energy at the rate of square of the speed of light.
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Experimental mass measure of a nucleus can be less than the theoretical prediction
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Mass Deficit ⇒ Nuclear Energy
huge to keep the positively charged protons that repulse each other in the nucleus.
short-ranged as it applies within a nucleus and does not interfere with electrons.
A balance of energies in a nucleus make it stable.
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Nuclear energy pulls protons, electrical energy pushes protons
Neutrons are subject to nuclear energy but not to electrical energy
# of
protons
# of
neutrons
# of stable
nuclei
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Even
Even
156
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Even
Odd
48
Odd
Even
50
Odd
Odd
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Technetium (Tc) has 43 (odd) protons and isotopes with 47 - 67 neutrons;
all isotopes are unstable.
Promethium (Pm) has 61 (odd) protons and isotopes with 65 - 102 neutrons;
all isotopes are unstable.
238
Uranium (U) has 92 (even) protons and has isotopes 𝑈92
with 146 (even)
235
neutrons and 𝑈92 with 143 (odd) neutrons.
238
235
𝑈92
also called U-238 is stable; 𝑈92
also called U-235 is unstable.
Instable nuclei tend to have odd numbers of protons and nucleons and they are potential nuclear fuel.
Instable nuclei release particles (splitting) or combines with other particles to achieve stability and
releases significant amount of energy
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Chemical Energy
Nuclear Energy
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Summary
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