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Compare the amount of mass converted to energy in nuclear

Conceptual Physics | 12th Edition | ISBN: 9780321909107 | Authors: Paul G. Hewitt ISBN: 9780321909107 29

Solution for problem 30RQ Chapter 35

Conceptual Physics | 12th Edition

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Conceptual Physics | 12th Edition | ISBN: 9780321909107 | Authors: Paul G. Hewitt

Conceptual Physics | 12th Edition

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Problem 30RQ

Compare the amount of mass converted to energy in nuclear reactions and in chemical reactions.

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In nuclear reactions, the nuclei of atoms themselves undergo changes. The number of protons and/or neutrons in the nucleus actually changes, meaning that the atom is transmuted into a different element. This result is impossible with chemical reactions, which is why alchemists in the Middle Ages were never able to transmute lead into gold. There are three basic types of nuclear reactions: radioactive decay, fission and fusion. In all three cases, the mass of the products are not equal to the mass of the reactants, something which never happens during chemical reactions. In any nuclear reaction, a very small portion of the matter in the reactant nuclei is transformed into pure energy according to Einstein's famous E=mc equation. This equation means that the amount of energy created is equal to the mass lost multiplied by the speed of light squared--an incredible amount of energy from a small amount of matter. Nuclear reactions are kind of in the middle between the two extremes of chemical reactions and elementary particle reactions. In an atomic nucleus, the binding energy contributes anywhere from 0.1% up to about 1% of the total energy of the nucleus. This is a lot less than with the color force in the proton, but it's still enough that it needs to be counted as a contribution to the mass of the nucleus. So that's why we say that mass is converted to energy in nuclear reactions: the "mass" that is being converted is really just binding energy, but there's enough of this energy that when you look at the nucleus as a particle, you need to factor in the binding energy to get the right mass. That's not the case with chemical reactions; we can just ignore the binding energy when calculating masses, so we say that chemical reactions do not convert mass to energy. It is believed that when an atomic bomb explodes, matter is transformed into enormous amounts of energy. This is not true. After the explosion, all of the original matter still exists. All of the protons, electrons, and neutrons making up the uranium, plutonium, or tritium are still within the mushroom cloud. Elements were transformed, neutrons were split into protons and electrons, and protons and electrons combined into neutrons, but in no case was a single particle of matter converted into energy. All of the original components needed to reconstruct the transformed atoms to their initial nuclear states are speeding away in all directions and could, in principle, be reassembled back into the original nuclei. The same exact number of protons and electrons exists after the explosion as existed before. To reassemble these components would require the same amount of kinetic energy that was released in the explosion. The energy of the explosion comes not from converting matter to energy, but from the kinetic energy released when the light elements combine and when very heavy elements break apart. This energy did not just appear from a miraculous transformation of matter into energy, but was always contained within the internal motions of the electrons and protons making up the structure of the fissioning or fusing atoms. The only transformation that occurred was the conversion of rotational kinetic energy into linear kinetic energy. Chemical reactions can either be endothermic, meaning that they absorb energy, or exothermic, meaning that they release energy. Whether a reaction is endothermic or exothermic depends on how much energy is contained in the chemicals before the reactions occurs (called reactants) and how much energy the chemicals have after they have reacted (called products). Gasoline, for example, contains much more energy than carbon dioxide, water vapor and other products of the reaction. All of the energy that is released or absorbed by a chemical reaction is due to different energies or stabilities of different arrangements of atoms. The mass of the products is always exactly equal to the mass of the reactants. Nothing is destroyed or created, only moved around. Chemical reactions are also mostly driven by the electrons surrounding each atom. The nuclei themselves never get close enough to each other to react. Rest mass is not additive. The rest mass of a molecule is not the sum of its atoms, but the sum plus the bond energy divided by c2c2. Therefore in a chemical reaction, though the number of atoms (or electrons, protons, neutrons) are conserved, the rest mass is not, since the bond energy is changed. And this can be called mass being converted into energy. In Motional mass, however, is just another name for energy, and therefore always conserved. In combustion, the molecular bond energy is converted to the additional kinetic energy of CO 2 CO2 molecules, so the mass(or energy) is conserved. In nuclear reaction, the electromagnetic and strong potential energy between nucleons are converted into the kinetic energy of new nuclei and (sometimes) flying neutrons. Sometimes the new nuclei are in excited state, and will soon emit gamma radiation, which are basically high energy photons with zero rest mass but nonzero motional mass.

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Chapter 35, Problem 30RQ is Solved
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Textbook: Conceptual Physics
Edition: 12
Author: Paul G. Hewitt
ISBN: 9780321909107

The full step-by-step solution to problem: 30RQ from chapter: 35 was answered by , our top Physics solution expert on 04/03/17, 08:01AM. This full solution covers the following key subjects: reactions, Energy, Compare, converted, chemical. This expansive textbook survival guide covers 45 chapters, and 4650 solutions. Since the solution to 30RQ from 35 chapter was answered, more than 255 students have viewed the full step-by-step answer. Conceptual Physics was written by and is associated to the ISBN: 9780321909107. The answer to “Compare the amount of mass converted to energy in nuclear reactions and in chemical reactions.” is broken down into a number of easy to follow steps, and 15 words. This textbook survival guide was created for the textbook: Conceptual Physics, edition: 12.

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