Figure 2
Figure 3
A nuclear physicist did experiments, which involve bombarding atoms of heavy elements with low energy neutrons. Neutrons are uncharged and so are not deflected by the electrically charged electrons outside or by protons inside nuclei. This makes them good ammunition for hitting an atomic nucleus hoping it would fuse with it and make the nucleus heavier. The physicist hoped to make heavier new elements than uranium.
Nuclear fission reactions differ from radioactive decay, both in a way which the reaction must be started and in the type of products formed. It can be harnessed and controlled via a chain reaction: free released by each fission event can trigger yet more events, which in turn release more neutrons and cause more fission.
Figure 4
The role of hydrogen nuclei and helium nuclei in the synthesis of elements in stars. Hydrogen and helium are the most abundant elements. All other elements are synthesized by fusion during the life and death of stars. Heavier chemical elements like lithium are made from these simple elements in a variety of processes collectively called nucleogenesis. A star obtains its energy by fusing together light nuclei to form heavier nuclei; in this process, mass (m) is converted into energy (E) in accordance with Einstein's formula, E=mc2, in which c is the speed of light. The closest star to earth consists of hydrogen which is converted into helium in the nuclear fusion reactions.
Figure 6
A nuclear fusion reaction is the process which two small nuclei combine under extreme temperatures and pressures to form larger nuclei’s. A small amount of mass is lost in fusion and transformed into energy. Under proper conditions, two deuterium nuclei may undergo fusion and produce a helium nucleus.
Figure 7
Lithium could be produced by the action of the energenetic cosmic rays on elements like carbon, nitrogen and oxygen. A small amount of lithium can be synthesised in supernovae, in which the heavier elements can be created. The nuclei of hydrogen are being formed into helium and these helium nuclei’s are being fused into lithium. Lithium can also be formed in stars by the formation of 8Be from helium-4 and helium-3 and then a collision between a Be atom and an electron causing a change in the nucleus. The proton number decreases by 1 and the structure is altered.
The main characteristics of fission reactions are that nuclear fission can produce two or three more neutrons and releases a large quantity of energy. The energy produced from the direct conversion of some nuclear mass into energy, is Einstein’s equation E=mc2. E is the energy, m is the mass and c is the velocity of light.
The nuclear fission process is thought like an alternation of a drop of liquid, if vibrations are fierce enough the liquid droplets can split like the diagram below:
Figure 8
Figure 8
The huge amounts of energy released from fission reactions can be used to provide electricity or during the war as an atomic bomb.
Nuclear fission is used to generate electricity. The fission process starts by the neutrons slowly moving hitting the nucleus of an atom. Each of the nucleuses splits producing three neutrons each, creating a chain reaction, if it is unchecked it causes the process to accelerate and become very out of control. This process was similar to the one used to make the first nuclear bombs. To generate the electricity, nuclear fission reactions are controlled in a nuclear reactor. The first of the nuclear reactors used a mixture of uranium isotopes and.
doesn’t go through fission in the reactor, as neutrons collide with the isotope, they are harmlessly absorbed and the chain reaction is interrupted.
Figure 9
Figure 9.1
The characteristics of nuclear fusion are the process by which multiple atomic particles join together to form a heavier nucleus. Fusion reactions power the stars and produce all but the lightest elements in a process called nucleosynthesis. The fusion of light elements in the stars releases energy. When the fusion reaction is a sustained uncontrolled chain, it can result in a thermonuclear explosion; it can be generated by a hydrogen bomb. Reactions which are not self-sustaining can still release considerable energy, as well as large numbers of neutrons.
Figure 10
The electrostatic force caused by positively charged nuclei is very strong over long distances, but at short distances the nuclear force is stronger. As such, the main technical difficulty for fusion is getting the nuclei closes enough to fuse.
When fusion reactions undergo the right conditions, deuterium and tritium atom fuse to form a helium atom and a neutron.
Figure 11
If the fusion reaction could be controlled on earth, the energy given out could potentially be used to generate the electricity. The only problem that the scientists come across is to reproduce the fusion reactions under safely managed conditions.
Figure 12
References:
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Figure1: from article 1, advanced subsidiary GCE, Chemistry Salters, skills for chemistry: open book exam, OCR
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Figure 2: from article 1, advanced subsidiary GCE, Chemistry Salters, skills for chemistry: open book exam, OCR
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Figure 3: from article 1, advanced subsidiary GCE, Chemistry Salters, skills for chemistry: open book exam, OCR
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Figure 4: from article 1, advanced subsidiary GCE, Chemistry Salters, skills for chemistry: open book exam, OCR
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Figure 5 : en.wikipedia.org/wiki/Nuclear_fission
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Figure 6: from article 2, advanced su subsidiary GCE, Chemistry Salters, skills for chemistry: open book exam, OCR
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Figure 7: from article 2, advanced su subsidiary GCE, Chemistry Salters, skills for chemistry: open book exam, OCR
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Figure 8: from article 1, advanced subsidiary GCE, Chemistry Salters, skills for chemistry: open book exam, OCR
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Figure 9 and 9.1: from article 1, advanced subsidiary GCE, Chemistry Salters, skills for chemistry: open book exam, OCR
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Figure10: en.wikipedia.org/wiki/Nuclear_fusion
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Figure 11: from article 2, advanced su subsidiary GCE, Chemistry Salters, skills for chemistry: open book exam, OCR
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Figure 13:http://www.scienceinschool.org/repository/images/fusion_JET_interior.jpg
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