boyle's law thermodynamics lab Boyle’s law, also called Mariotte’s law, a relation concerning the compression and expansion of a gas at constant temperature. This empirical relation, formulated by the physicist Robert Boyle in 1662, states that the pressure (p) of a given quantity of gas varies inversely with its volume (v) at constant temperature; i.e., in equation form, pv = k, a constant. The relationship was also discovered by the French physicist Edme Mariotte (1676). ake a large piston or sealed syringe and stand it on end, then place an increasing number of objects on top. As the pressure grows, the volume of the air inside will decrease—these quantities are inversely proportional. However, the standard international unit for pressure is the Pascal. The English scientist Robert Boyle performed a series of experiments involving pressure and, in 1662, arrived at a general law—that the volume of a gas varies inversely with pressure.

1. Koya university
faculty of engineering
Chemical engineering department
thermodynamics
Boyle’s Law: Pressure-Volume Relationship in Gases
2022-2023
Prepared by : supervised by:
Dima Jawhar Mustafa Mr. Ribwar Krmanj
Mr. Rebwar Abrahim
Experiment date : 19/oct./2022 Submitting date : / /

2. Boyle’s Law: Pressure-Volume Relationship in Gases
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Table of Contents
Purpose of experiment : ................................................................................................................................3
Introduction:..................................................................................................................................................3
WL 102 description : ....................................................................................................................................4
Theoretical ....................................................................................................................................................6
Observations : Experiment type : Isothermic expansion : ............................................................................8
Materials Required:...................................................................................................................................8
Table of reading and experiment data :...................................................................................................10
Discussion:..................................................................................................................................................11
References :.................................................................................................................................................13

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Purpose of experiment :
The primary objective of this experiment is to determine the relationship between the pressure and
volume of a confined gas. The gas we use will be air.
Introduction:
Robert Boyle discovered the volume and pressure of gasses are inversely proportionate when held at a
constant temperature in 1662.
The WL 102 machine is for demonstrating Boyle’s law and checking the state equation for ideal gases. It
clearly shows the relationship between change in volume and the associated change in pressure of an
enclosed gas. The gas that is used will be air, The sealing liquid works like a piston. It enlarges or reduces
the enclosed gas volume. The processes during the experiment are sufficiently slow to ensure isothermic
changes. a change occurs in the pressure exerted by the confined gas. This pressure change will be
monitored by using a sealing liquid that works like a piston. this can be compressed or expanded in a
perspex vessel. In this experiment the data that is collected will be from expending the gas (air) As an
alternative, during this experiment a fixed volume of air is expanded and the change in pressure plotted.
,It is assumed that temperature will be constant throughout the experiment. Pressure and volume data
pairs will be collected during this experiment and then analyzed. From the data and graph, you should be
able to determine what kind of mathematical relationship exists if it is inverse or direct between the
pressure and volume of the confined gas.

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WL 102 description :
Unit Design and Function : WL 102 :
Figure-1 :The experiments on the WL 102 are performed in two different vessels. A liquid can be pumped
into a pressure cylinder (1) with the aid of a compressor. In this manner, the volume of air enclosed in the
cylinder is compressed.
The advantages of this technique are, firstly, the gastight sealing liquid which prevents losses through
leakages in air flow and, secondly, heat sink effect which contributes significantly toward isothermal
testing characteristics.

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Displays for temperature, pressure and compressed volume (2) indicate the corresponding values
measured in the vessel. The selector switch (4) is used to switch between compression and expansion of
the air inside the pressure vessel. A switch (3) is used to turn on the compressor.
In a second, heatable cylinder (5), a closed, constant volume of air is heated and the resulting change in
pressure observed. The heater is activated with a switch (8).
A heater control (7) permits adjustment of the desired temperature by means of upward and downward
arrow keys and indicates the actual temperature. The parameter to be selected by pressing the upward and
downward arrow keys. Dynamically alteration of parameter to be made by pressing the key for as long as
the key is kept pressed. For manually taking over of entry the „P“ key to be pressed. After 2s the entry
will be automatically adopted.
For cancelling the entry the Exit/F key to be pressed. Change to the manual mode using function key
Exit/F (> 2s). Exit the manual mode using function key Exit/F (> 2s).
The resulting pressure inside the cylinder is indicated by a display (6). The experimental unit is switched
on and off using the main switch (9). On the rear of the unit is a USB port which can be used to connect
the unit to the PC via cable.
Figure-2:parts of WL 102.

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Theoretical
In every gas there is a certain pressure. If the volume of an enclosed quantity of gas is reduced by
compression, this pressure increases. If the volume is increased, the pressure drops. Boyle’s law describes
this relationship:
p V const.  = T = const.
The product of pressure and volume is constant. The two parameters are inversely proportional to each
other.
This law is, however, only applicable if the amount of gas and the temperature do not change.
During the performance of the experiments, the heat produced by the compression can produce erroneous
results. The experiment must therefore be performed sufficiently slowly that the temperature remains
constant. In this case the term isothermic change of state is used.
The value for the constant (p x V) represents, in formal terms, an energy parameter, the so-called internal
energy.
Strictly, Boyle’s law only applies for ideal gases. If noticeable deviations occur, the term real gas is used,
in the case of large deviations - vapour.
In the case of values for pressure and temperature in the range of normal conditions, e.g., air, hydrogen
and the noble gases behave like ideal gases, chlorine and carbon dioxide like real gases, propane and
butane like vapours.
A further relationship is described by the GayLussac law. This states that if a fixed quantity of gas is
contained in a constant volume, the pressure is proportional to the absolute temperature.
The combination of both laws leads to the general gas equation:

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For a fixed quantity of gas, the expression
(p x V) / T always remains constant.
Figure-3: Pressure-Volume Relationship graph.

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Observations : Experiment type : Isothermic expansion :
Materials Required:
1. WL 102
2. Sample experiment : Air
In this experiment, to check Boyle’s law a fixed quantity of gas of approx. 3 litre volume is compressed to
approx at a certain volume leave of the perspex vessel by filling the liquid to work as a piston. Then will
be observed as the gas (Air) will be expanded carefully, so that the Pressure and volume data pairs can be
collected during this experiment and then analyzed.
NOTICE
Risk of escape of the sealing liquid.
• Open the air discharge valve slowly.
• Carefully open the air discharge valve (10) on the lid of the pressure cylinder and release the
compressed air until ambient pressure is reached.
• Close the air discharge valve again.
• Open the needle valve (12) and set the required filling speed.
• Move the selector switch (4) to position B.
• Start the data acquisition program and make the corresponding settings.
• Turn on the compressor and expand the gas volume until the 3L mark on the vessel scale (11) is
reached.
• Open the graph of measured values and interpret.
• Carefully open the air discharge valve on the lid of the pressure cylinder and allow air to flow into
pressure cylinder until ambient pressure is reached.
Similar to the compression experiment, this experiment produces a comparable measured result.

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Figure-4: graph from the collection data from the experiment.

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Table of reading and experiment data :
Pressure (Bar) Volume(Air)- (L)
2.13 1.38
1.80 1.62
1.45 1.98
1.14 2.49
0.99 2.9
Figure-5: To confirm that an inverse relationship exists between pressure and volume, a graph of pressure vs.
reciprocal may also be plotted according to the experiment data.

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Discussion:
1. Discuss if there will be any error in the experiment.
Error may happen in the experiment, thus the collection of the data may be different from the
standard information , They might come from: uncalibrated instruments (balances, etc.), impure
reagents, leaks, unaccounted temperature effects, biases in using equipment, mislabelled or
confusing scales, seeing hoped-for small effects, or pressure differences between barometer and
experiment caused by air conditioning.
2. Is there any deference between the compression exp. And expansion exp.?
compression exp.1 :
the exp. Sample (gas/Air) will behave on room pressure ,carefully increasing pressure as the
liquid level in the perspex vessel which acts like a piston will rise with each mL level ,the
pressure is controlled and then observing the volume of the the sample so as the data is collected.
Explanation exp.2 :
the exp. Sample (gas/Air) will already be compromised in the perspex vessel the liquid level will
be at a high level before starting the exp. Carefully the liquid will be decreased, the volume of
the air will be controlled at certain times because of the liquid which acted like a piston in the
first exp. So that the pressure is observed then data will be collected.
3. What experimental factors are assumed to be constant in this experiment and why?
It is assumed that temperature will be constant throughout the experiment. Pressure and volume
data pairs will be collected during this experiment and then analyzed.
4. What does the table of reading and experiment data shows ?
As The volume of the Air increases the pressure decrease.
5. To confirm that an inverse relationship exists between pressure and volume, a graph of pressure
vs. reciprocal of volume may also be plotted.
It is shown in Figure-5.
6. What’s the conclusion of the experiments, what do they achieve?
If the volume of the gas decreases, the pressure of the gas increases. If the volume of the gas
increases, the pressure decreases. These results support Boyle's law.

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7. why is boyle's law important?
Boyle's law is significant because it explains how gases behave. It proves beyond a shadow of a
doubt that gas pressure and volume are inversely proportional. When you apply pressure on a gas,
the volume shrinks and the pressure rises.
This expression can be obtained from the pressure-volume relationship suggested by Boyle’s law.
For a fixed amount of gas kept at a constant temperature, PV = k, P1V1 = P2V2
8. Discuss Different Boyle’s law applications in real life.
Spray paint, Soda bottle, Diving into deep water…etc.

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