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Van der Waals (Van der Waals), Jan Diederik

( Nederlands physicist, Nobel Prize in Physics, 1910)

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Biography Van der Waals (Van der Waals), Jan Diederik
November 23, 1837, Mr.. - March 8, 1923
Netherlands physicist Jan Diederik van der Waals was born in Leiden, the son of Jacobus van der Waals, a carpenter, and Elizabeth Van der Waals (nцLe Van den Burg). After primary and secondary school in Leiden, Jan became a teacher of primary school. From 1862 to 1865. He attended the University of Leiden as irregular. In 1864, Mr.. He received the certificate of secondary teachers in mathematics and physics and taught physics, first in Deventer in 1864, and then in The Hague, where he began in 1866, Mr.. principal.
Shortly thereafter, he began graduate work in physics and received his doctorate at Leiden in 1873,. His thesis, . devoted to the continuity of the gaseous and liquid states, . received a warm approval of the James Clerk Maxwell, . one of the greatest physicists of the XIX century., . who said of the VA: 'She immediately put his name on a par with the most prominent names in science',
. This thesis, which was later translated into German and French languages, not only approved a reputation. as a brilliant physicist, but also identified the object of his research until the end of his scientific activity. Four years after receiving his doctorate, he became the first professor of physics at the newly organized University of Amsterdam, where he remained until the very resignation in 1908, handing over his business to his son.
Eden. emerged under the influence written in 1857. Articles by Rudolf Julius Emanuel Clausius, German physicist, who made a great contribution to the kinetic theory of gases. According to this theory, the gas molecules are moving rapidly in different directions. They were pounding on the walls of the vessel containing them determine the gas pressure, and the average velocity of the molecules (their kinetic energy) is directly related to the temperature. Clausius showed how you can use this theory to deduce the law, found experimentally in 1662, Mr.. (when more was known about the molecules), Robert Boyle, Irish physicist and chemist. Boyle's Law states that for a given mass of gas at a constant temperature the product of pressure on the volume constantly. If, for example, the volume decreases due to the fact that the cylinder moves into the piston, the pressure increases to such an extent that has remained steady this product. Later, in the XIX century., Other scholars, such as, a French physicist Jacques Alexander Cesar Charles and Joseph Louis Gay-Lussac showed that at constant pressure, the ratio of the absolute temperature remains constant. This law can also be derived directly from the kinetic theory. These two laws can be combined into a single equation of state, which is valid at not too high density: PV = RT, where P - pressure.
V - volume, T - absolute temperature, absolute zero, ie. -273 б¦ C, a R - a constant value for all gases, if the volume contains at least one gram-molecule of gas.
It was known that this equation is not quite accurate, and in varying degrees for different gases and different conditions. Gases that best satisfy this equation are called ideal. Investigating possible sources of errors in. noticed, . that the equation was based on two assumptions: that the molecules act as a point mass (which roughly corresponds to reality, . if they are removed from each other) and that the molecules have no effect on each other (except for collisions),
. He entered the final volume for each molecule and the force of attraction between molecules (without specifying its nature), which reduces the increasing distance. (Other researchers later found out the details, but a weak non-chemical attraction between molecules is still often referred to by Van der Waals forces.) Then, in. deduced the modified equation of state of real gas: (P + н¦ / н+ (н+ - н¦) = RT, where н¦ is the mutual attraction of molecules of gas (divided by н+2, to take into account the weakening of this force at a higher level, ie. with greater average distance between molecules), and P is the molecular volume. As н¦, and P take different values for different gases.
Although the equation of van der Waals forces and does not fully satisfy the experimental data, it was a significant improvement over the simple law and have important consequences. The attraction between molecules leads to the fact that in. called the internal pressure, which tends to hold the molecules together. As the volume decreases under external pressure, internal pressure increases much faster than the external. If it will be equal to or exceed the external pressure, the molecules become stuck together and they will not need more pressure from the vessel containing them. Gas becomes a liquid. This illustrates the belief VI, expressed in his thesis that between the gaseous and liquid states is no significant difference. Those same forces and the effects of molecular volume are in both cases. The difference between the properties of gases and liquids due to the difference in magnitude, but not in the type of forces and volume effects, since the molecule can be positioned closer or farther from each other.
. Van der Waals significantly clarified the previously discovered the existence of the critical temperature, different for different gases, above which the gas, regardless of the pressure, it was impossible to translate into a liquid state
. The critical temperature associated with the critical volume and critical pressure, . which together determine the critical point, . set of special values of the temperature, . pressure and volume, . in which there is no visible distinction between gas and liquid: under these conditions, both states are roughly the same, . sharp transition between them,
. V. used a critical point in order to derive an equation in which variables are temperature, pressure and volume are expressed in terms of their values at the critical point. The result is a universal relationship that applies to all gas and power in each case only on the critical temperature, pressure and volume, and not the nature of the gas.
This was the basis for the formulation in 1880. his most important discovery - the law of corresponding states. According to this law, . if the behavior of some gas and associated liquid is known at all temperatures and pressures, . the state of any other gas or liquid can be calculated for any temperature and pressure, provided, . is known of their status at the critical temperature,
. This law is not a perfect description of the extremely complex nature of gases and liquids, . but it is sufficiently robust to, . to approximately determine the conditions, . necessary for the liquefaction of gases, . building on existing experimental data,
. Guided by this law, the Scottish physicist James Dewar in 1898. received liquid hydrogen, and Kamerlingh Onnes, Netherlandish counterpart, Vladimir, in 1908, Mr.. received liquid helium.
In his further studies in. tried to take into account deviations from the equation of state of real gas, by introducing a variable molecular volume. He suggested that the molecules are capable of forming a cluster, which then behaves as a single molecule of larger. Since the cluster could contain any number of single molecules, the gas can become a complex mixture. Although the original equation in. remains useful in a number of cases, its simplicity has largely been sacrificed to more accurately describe the behavior of gas.
In. received in 1910. Nobel Prize in Physics "for his work on the equation of state of gases and liquids'. According to Oscar Montelius, a member of the Royal Swedish Academy of Sciences, during the presentation of the winner, 'Research in. are of great importance not only for pure science. The modern design of refrigeration units that are now so powerful factor in our economy and industry, based mainly on theoretical research awarded '.
In. married Anna Magdalena Smit in 1864. She died when their three daughters and son were still very young, and he never married. A short man, who kept a modest lifestyle in. spent his spare time playing billiards, reading or playing patience. He died in Amsterdam in 1923. V. received an honorary doctorate at Cambridge University. In addition, he was a member of the Royal Netherlands Academy of Arts and Sciences and was elected a foreign member of the French Academy of Sciences. Berlin Royal Academy of Sciences. Moscow Imperial Society of Naturalists, the British and the American Chemical Society National Academy of Sciences

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