3.3. For questions 1-13, read the text below. Use the word given in capitals at the end of the lines to form a word that fits in the same line. Sound, Chemical and Nuclear Energy
The fact that people can hear is a simple (1)………….. of the fact that sound is a form of energy. Sound is actually nothing other than the (2)………… of air. When sound is created, sound waves travel through space, creating compressions in some regions. When these sound waves strike the human eardrum, they cause the drum to (3)…………., creating the sensation of sound in the brain. Similar kinds of sound waves are (4)……………. for the destruction caused by explosions. The sound waves collide with building, trees, people, and other objects, causing damage to them.
Chemical energy is a form of energy that results from the forces of (5)……….. that hold atoms and other particles together in molecules. In water, for example, hydrogen atoms are joined to oxygen atoms by means of strong forces known as chemical bonds. If those are broken, the forces are released in the form of chemical energy. When a substance is burned, chemical energy is released. Burning (combustion or (6)……..) is the process by which chemical bonds in a fuel and in oxygen molecules are broken and new chemical bonds are formed. The total energy in the new chemical bonds is less than it was in the (7)…………… chemical bonds, and the (8)…………… is released in the form of chemical energy.
Nuclear energy is (9)……………. to chemical energy except that the bonds involved are those that hold together the particles of a nucleus, protons and neutrons. The fact that most (10)………… nuclei are stable is (11)……… that some very strong nuclear forces exist. Protons are positively charged and one would expect that they would repel each other, blowing apart a nucleus. Since that does not happen, some kinds of force must exist to hold the nucleus together.
One such force is known as the strong force. If something happens to cause a nucleus to break apart, the (12)…………. force holding two protons together is released in the form of nuclear energy. That is what happens in an atomic (fission) bomb. A uranium nucleus breaks apart into two (13)………… equal pieces, and some of the strong force holding protons together is released as nuclear energy. |
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3.4. Read the text below and find antonyms to the following words:
analysis
to multiply
remote
above
higher
unimportant
light
seldom
The Most Tightly Bound Nuclei
The most tightly bound of the nuclei is 62Ni, a case made convincingly by M. P. Fewell in an article in the American Journal of Physics. Though the championship of nuclear binding energy is often attributed to 56Fe, it actually comes in a close third. The four most tightly bound nuclides are listed in the table below with a tabulation of the binding energy B divided by the mass number A. The curve adapted from Fewell shows those nuclides that are close to the peak.
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The most tightly bound nuclides are all even-even nuclei. The curve drawn through the cluster of nuclei above is just to show the nature of the trend with mass number. A similar kind of trend is observed with even-odd nuclides at a lower range of binding energy, and then by odd-odd nuclei at the least-bound extreme. The peaks of all three groups occur around A = 60.
The high binding energy of this group of elements around A=60, typically called "the iron group" by astrophysicists, is significant in the understanding of the synthesis of heavy elements in the stars. It is curious that the abundance of 56Fe is an order of magnitude higher than that of 62Ni. Fewell discusses this point, and indicates that the reason lies with the greater.