Five Main Reasons for using Vacuum - Part 5 - by Howard Tring This article completes the series of Five Main Reasons that vacuum is used in science and industry; To provide a working force, to remove active and reactive constituents, to remove trapped and dissolved gases, to decrease thermal transfer and finally to increase the mean free path to a useful dimension. The article printed back in January this year talked about solid, liquid and gas states of matter. The following is a short excerpt from that article. “In a gas the atoms and molecules are generally much further apart than in solids and liquids. In air at atmospheric pressure and room temperature the actual space occupied by atoms and molecules is about 0.01 per cent or one ten thousandth of the volume. The equivalent for solid copper is about 74 percent or close to three quarters. (So much for being called a “solid”). In air the molecules are in constant random movement, typically in a straight line, and the interatomic forces have little effect due to the space between the molecules. The moving molecules will constantly collide with other molecules and then move away in a different direction. These collisions occur about 10,000,000,000 times per second at atmospheric pressure”. goo.gl/cjn0RL
Posted on: Mon, 15 Sep 2014 14:41:31 +0000
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