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Search results 111 - 120 of 278 matching essays
- 111: The Depletion of Ozone Layer
- ... the stratosphere at altitudes between 15 and 50 kilometers in which the concentration of the ozone is raised. Ozone is a colorless gas, a form of oxygen. However, an ordinary molecule of oxygen contains two atoms. Because of ozone’s composition, it is reactive. It readily combines with whatever materials it comes in contact with, including such biological substances as cells and tissues. Far above the earth, ozone forms naturally as ... to the ozone layer is largely caused by the release of certain volatile chemicals in the halogenated hydrocarbons groups into the air. These are compounds of carbon and hydrogen which some or all the hydrogen atoms have been replaced by halogens, such as fluorine, chlorine and bromine. In 1974, F. Sherwood Rowland and Mario J. Molina, both in chemistry department of the University of California at Irvine released a study proposing ...
- 112: Cellular Respiration
- ... of 2 ATP have been formed. As the pyruvic acid molecules make their way toward the mitochondria, two more molecules of NADH are formed. A carbon atom also breaks off and combines with two oxygen atoms to produce the waste product carbon dioxide. As a result of these reactions, each pyruvic acid molecule is transformed into a two-carbon compound called an acetyl group. The two acetyl groups combine with a ... molecules of ATP, and additional carbon dioxide are all formed. FAD picks up a hydrogen atom from each pyruvic acid molecule, and a total of 2 FAD2 are formed. NADH and FAD2 transport their hydrogen atoms and electrons to the electron transport chain. The electrons are passed down the chain of attracting molecules until they reach oxygen. Joined with hydrogen, they combine with the oxygen to form water. As the electrons ...
- 113: The Threat of Nuclear Energy
- ... happens in a nuclear reaction. Ann E. Weiss, who has written several books on the subject of nuclear energy, described what happens inside a nuclear power plant. In a nuclear reaction the nuclei of its atoms split, producing energy in the form of heat. The heat makes steam which powers a turbine. Fission takes place in a nuclear reactor. The fuel used is pellets of uranium. In a modern reactor, half ... Once this is done a single free neutron is enough to set off the reaction. As the reaction continues, a moderator slows the neutrons down enough to ensure that they will continually split more uranium atoms. At the same time, the moderator acts as a coolant. It keep the overall temperature about 300 degrees Celsius. Since the temperature at spots inside the fuel rods may be as high as 1,100 ...
- 114: Acid Rain
- ... other chemical that is also chiefly responsible for the make-up of acid rain is nitrogen oxide. Oxides of nitrogen is a term used to describe any compound of nitrogen with any amount of oxygen atoms. Nitrogen monoxide and nitrogen dioxide are all oxides of nitrogen. These gases are by-products of firing processes of extreme high temperatures (automobiles, utility plants), and in chemical industries (fertilizer production). Natural processes such as ... common process is when sulfur dioxide reacts with moisture found in the atmosphere. When this happens, sulfate dioxide immediately oxidizes to form a sulfite ion. Afterwards, it becomes sulfuric acid when it joins with hydrogen atoms in the air. A common reaction for sulfur dioxide to becomes sulfuric acid is by oxidation by ozone. This reaction occurs at a preferable rate and sometimes is the main contributor to the oxidation of ...
- 115: The Beginning Of The Universe
- ... then electrons, and finally neutrinos. After about an hour, the temperature had dropped below a billion degrees, and protons and neutrons combined and formed hydrogen, deuterium, helium. In a billion years, this cloud of energy, atoms, and neutrinos had cooled enough for galaxies to form. The expanding cloud cooled still further until today, its temperature is a couple of degrees above absolute zero. In the future, the universe may end up ... expanding infinitely into the darkness. This space will become even emptier, as the fundamental particles of matter age, and decay through time. As the years stretch on into infinity, nothing will remain. A few primitive atoms such as positrons and electrons will be orbiting each other at distances of hundreds of astronomical units.7 These particles will spiral slowly toward each other until touching, and they will vanish in the last ...
- 116: Electrolytes
- ... barely dissolvable are weak. The strength of an electrolyte is measured by its ability to conduct electricity. There’s also the way of Ionization of Polar Covalent Molecular Substances. Polar molecular substances are substances whose atoms are co- valently bonded. Each molecule has a net molecular dipole moment (the product of the distance between two poles of a dipole and the magnitude or either pole) that is made because of the ... attraction is called intermolecular force, This force can overcome the dissociation energy of a bond within the polar molecule. The dissociation energy is the least amount of energy needed to break a bond between two atoms. If this happens then the polar molecule will fragment with the broken bond. This will make ions where there wasn’t any to begin with. This is called ionization, and will end up with ions ...
- 117: The Big Bang and Steady State Models
- ... then electrons, and finally neutrinos. After about an hour, the temperature had dropped below a billion degrees, and protons and neutrons combined and formed hydrogen, deuterium, helium. In a billion years, this cloud of energy, atoms, and neutrinos had cooled enough for galaxies to form. The expanding cloud cooled still further until today, its temperature is a couple of degrees above absolute zero. In the future, the universe may end up ... expanding infinitely into the darkness. This space will become even emptier, as the fundamental particles of matter age, and decay through time. As the years stretch on into infinity, nothing will remain. A few primitive atoms such as positrons and electrons will be orbiting each other at distances of hundreds of astronomical units.7 These particles will spiral slowly toward each other until touching, and they will vanish in the last ...
- 118: The Big Bang and The Steady State Model
- ... then electrons, and finally neutrinos. After about an hour, the temperature had dropped below a billion degrees, and protons and neutrons combined and formed hydrogen, deuterium, helium. In a billion years, this cloud of energy, atoms, and neutrinos had cooled enough for galaxies to form. The expanding cloud cooled still further until today, its temperature is a couple of degrees above absolute zero. In the future, the universe may end up ... expanding infinitely into the darkness. This space will become even emptier, as the fundamental particles of matter age, and decay through time. As the years stretch on into infinity, nothing will remain. A few primitive atoms such as positrons and electrons will be orbiting each other at distances of hundreds of astronomical units.7 These particles will spiral slowly toward each other until touching, and they will vanish in the last ...
- 119: Surface Tension
- ... pull on the surface molecules, and also in the transformation of a liquid into a solid state when the molecules are brought sufficiently close together. Cohesion in solids depends on the pattern of distribution of atoms, molecules, and ions, which in turn depends on the state of equilibrium (or lack of it) of the atomic particles. In many organic compounds, which form molecular crystals, for example, the atoms are bound strongly into molecules, but the molecules are bound weakly to each other. Bibliography: Microsoft Encarta 95 1994 Funk & Wagnall's Corporation Encyclopedia Britannica 1988 vol.11 15th Edition Encyclopædia. Britannica, Inc. . Compton's ...
- 120: The Geiger-Muller Tube
- The Geiger-Muller Tube In the Geiger-Muller tube, particles ionize gas atoms. The tube contains a gas at low pressure. At one end of the tube is a very thin ”window” through which charged particles or gamma rays pass. Inside the tube is a copper cylinder with ... the wire. The positive ion produced is accelerated toward the copper cylinder by the potential difference. The electron is accelerated toward the positive wire. As these new particles move toward the electrodes, they strike other atoms and form even more ion in their path. Thus an avalanche of charged particles is created and a pulse of current flows through the tube. The current causes a potential difference across a resistor in ...
Search results 111 - 120 of 278 matching essays
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