20-09-2012, 11:41 AM
VERIFICATION OF BOYLE’S LAW
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Abstract
Using a J tube, containing air at atmospheric pressure, pressure is applied by placing weight on the piston. For different weights the air volume is noted and the product PV calculated. A graph of P versus V showed a parabolic variation and a graph of P versus (1/V) showed a straight line relation. The number moles of air enclosed and the number molecules enclosed are calculated using ideal gas equation.
Introduction
Boyle’s law is one of the earliest laws of physics and chemistry conducted by Robert Boyle in 1662. Robert Boyle employed a J-shaped glass tube that was sealed at on one end. A gas (air) was trapped in the sealed end of the tube and varying amounts of mercury, pressure is applied. Boyle systematically varied the pressure and measured the volume of the gas. These measurements were performed using a fixed amount of gas and a constant temperature. In this way Boyle was able to examine the pressure-volume relationship [1]. By this experiment he concluded that the product of pressure and volume is a constant. Or the pressure (P) is inversely proportional to volume (V).
Ideal gas law
The combined gas law or general gas equation is formed by the combination of the three laws, and shows the relationship between the pressure, volume, and temperature for a fixed mass of gas. It was first stated by Émile Clapeyron in 1834 as a combination of Boyle's law and Charles's law. August Krönig in 1856 and Rudolf Clausius in 1857[2] independently derived gas equations from kinetic theory of gases as,
Verification of Boyle’s law
Verification of Boyle’s law is one of the fundamental experiments in physics for plus-two classes as it is now in the common all India plus-two syllabus. There are two types of apparatus available for class room experiment in market. The first one uses a similar J-tube and mercury as done by Robert Boyle. However, use of mercury by student in class room is little risky because of its poisonous nature and if spill on floor removing and cleaning is utmost difficult. The second method uses a cycle pump and tube filled with water. The author is in possesses few of such pieces which are so called export pattern and found leaky and faulty. Hence we have designed new apparatus to verify Boyle’s law.
The apparatus consists of a syringe on stand fitted to glass tube through small rubber tube as shown in Figure-1. A stop cock is fitted to the open end of glass tube. The air inside the glass tube, rubber tube and syringe makes the total volume. The initial air pressure (atmospheric pressure) plus the pressure exerted through the piston of the syringe makes the total pressure. The volume and pressure can be varied and product ‘PV’ can be determined to verify Boyle’s law.