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A Connection of Ideal Gas Laws by Experiment

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Journal of National Taipei Teachers College, Vol. ⅩⅣ(Sep. 2001) 529~542 NATIONAL TAIPEI TEACHERS COLLEGE 17 A Connection of Ideal Gas Laws by Experiment Tzyh-lee Chang, Pi-ling Chang and Herbert C. Cheung∗ ABSTRACT Generally, we need to perform different experiments in order to examine Boyle’s law and the law of Charles and Gay-Lussac. In this work we proposed a method which could allow us to not only investigate the preceding two laws, but also extend a connection to all the other laws such a
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  Journal of National Taipei Teachers College, Vol. (Sep. 2001) 529~542 ⅩⅣ  NATIONAL TAIPEI TEACHERS COLLEGE17 A Connection of Ideal Gas Laws by Experiment Tzyh-lee Chang,  Pi-ling Chang  and  Herbert C. Cheung ∗ ABSTRACT Generally, we need to perform different experiments in order to examine Boyle’slaw and the law of Charles and Gay-Lussac.  In this work we proposed a method whichcould allow us to not only investigate the preceding two laws, but also extend aconnection to all the other laws such as Avogadro’s law, Dalton’s law, combined law,and the general form of ideal gas law.  An analysis of the data obtained in thisexperiment yields acceptable results.  For example, the conversion constant betweenthe Celsius and Kelvin scales was found to be 1.15% less than the true value(=273.15), and the universal gas constant was found to differ from the true value of 0.08206(L-atm/K-mol) by 1.16%.  If the idea of this experiment can be applied todesign a more feasible experiment for students to follow, students can not only learn allthe ideal gas laws, but also know how to apply them in practical situations. Key words: Boyle’s law, the law of Charles and Gay-Lussac, Avogadro’s law,Dalton’s law, combined law, the general form of ideal gas law.  Tzyh-lee Chang: Associate Professor, Department of Natural Science Education,NTTCPi-ling Chang: Assistant Professor, Department of Nutrition Sciences, the University of Alabama at BirminghamHerbert C. Cheung: Professor, Department of Biochemistry and Molecular Genetics, theUniversity of Alabama at Birmingham  18   Journal of National Taipei Teachers College, Vol. ⅩⅣ   Journal of National Taipei Teachers College, Vol. (Sep. 2001) 529~542 ⅩⅣ  NATIONAL TAIPEI TEACHERS COLLEGE19 A Connection of Ideal Gas Laws by Experiment Tzyh-lee Chang,  Pi-ling Chang  and  Herbert C. Cheung ∗ I. INTRODUCTION If one asks where the level of the water is inside a cylindrical bottle immersedupside down in a tank of water, many students will simply reply that the level of thewater inside the bottle is the same as the water level of the tank.  In fact, the water levelinside the bottle is below that of the water level of the tank.  This simple demonstrationcan motivate students to seek why there are differences in the water level.  As a matter of fact, it can be explained by the equilibrium of pressure which is reached between theinside pressure of dry air plus vapor pressure of water in the upside down cylindricalbottle and the external pressure of atmospheric pressure plus water pressure in the tank.Furthermore, with a few measurements on the different depths of the water levels bothinside and outside the cylindrical bottle, one can quantitatively link the experimentaldata to all the ideal gas laws.  The experimental method presented is simple in theory,safe and straightforward in practice. II.THEORY OF IDEAL GAS LAWS A sample of gas can be characterized by four variables: the volume V, thetemperature T, the pressure P, and the number of moles n.  For an ideal gas, simple  Tzyh-Lee Chang: Associate Professor, Department of Natural Science Education,NTTCPi-ling Chang: Assistant Professor, Department of Nutrition Sciences, the University of Alabama at BirminghamHerbert C. Cheung: Professor, Department of Biochemistry and Molecular Genetics, theUniversity of Alabama at Birmingham  20   Journal of National Taipei Teachers College, Vol. ⅩⅣ  relationships, known as the ideal gas laws, have been established concerning thesevariables:Boyle’s law P 1 V 1 =P 2 V 2 T and n constant  (1)Avogadro’s law V 1 /n 1 =V 2 /n 2 P and T constant  (2)Dalton’s law P 1 /n 1 =P 2 /n 2 V and T constant  (3)The law of Charles V 1 /T 1 =V 2 /T 2 P and n constant  (4)and Gay-Lussac P 1 /T 1 =P 2 /T 2 V and n constant  (5)Combined law P 1 V 1 /T 1 =P 2 V 2 /T 2 n constant  (6)These individual relationships imply a more general relationship:  PV=nRT,  (7)where R is known as the universal gas constant.  In this experiment we can study allthese laws from the experimental data.  In addition, we can also examine the quality of data by comparing the derived conversion constant between the Celsius and the Kelvinscale and the universal gas constant with well-known values of 273.15 and 0.08206L-atm/K-mol, respectively. III.EXPERIMENTAL SECTION Mercury has commonly been used to study the Boyle’s law in general science labs(Hermens, 1983; Hein, et al., 1992).  However, these experiments must be performedcautiously because spilled mercury can be very hazardous.  To keep away from danger,the use of hypodermic syringes was proposed instead (Davenport, 1962).  Boyle’s lawwas examined by taking the volume readings of a gas trapped in the syringe by pilingbooks onto the piston.  In addition, Charles’ law could also be examined by taking thevolume readings of a gas in a syringe which was immersed in a liquid bath maintainedat various temperatures (Davenport, 1962).  In our experiment we used water rather than mercury.  Thus our experiment has the same advantage of safety as the use of hypodermic syringes.  Furthermore, to the best of our knowledge our experiment hasbeen the first one reported so far that can lead all the ideal gas laws to be learned byone experiment.  In fact, the idea of our experiment was obtained from a previousstudy about the relationship between candle flame and oxygen (Chang, 1999).The equipment and materials used in our experiment include two thermometers (amercury thermometer and a digital thermometer, Sensortek model BAT-12), one

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Nov 20, 2017
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