Faulty of Engineering

School of Chemical&Petroleum Engineering

Chemical Engineering department

Laboratory of thermodynamics

EXPERIMENT NUMBER TWO

Boyles law (expansion)

Instructor: Mr rebwar&Mr umer

Author Name: shwan sarwan sadiq

Experiment Contacted on: 29/oct/2013

Report Submitted on: 12/nov /2013

Group:b

The aim of this experiment:

The purpose of Boyle's law is to set up a relationship

between the pressure and the volume of a gas.

The law states that as the pressure of a gas

increases,its volume decreases, and vice-versa.

Introduction

The ideal gas equation (PV=nRT) provides a valuable model of the

relations between volume, pressure, temperature and number of

particles in a gas. As an ideal model it serves as a reference for the

behavior of real gases. The ideal gas equation makes some

simplifying assumptions which are obviously not quite true. Real

molecules do have volume and do attract each other. All gases

depart from ideal behavior under conditions of low temperature

(when liquefaction begins) and high pressure (molecules are more

crowed so the volume of the molecule becomes important).

Refinements to the ideal gas equation can be made to correct for

these deviations.

Reference 1

Theory:

The kinetic theory of gases (also known as kinetic-molecular

theory) is a law that explains the behavior of a hypothetical ideal

gas. According to this theory, gases are made up of tiny particles

in random, straight line motion. They move rapidly and

continuously and make collisions with each other and the walls.

This was the first theory to describe gas pressure in terms of

collisions with the walls of the container, rather than from static

forces that push the molecules apart. Kinetic theory also explains

how the different sizes of the particles in a gas can give them

different, individual speeds

Boyle’s law states that for the pressure and volume of a gas,

when one value increases the other decreases, as long as

temperature and number of moles remain constant. Boyle's law

is summarized by the equation

PV=k

where P is the pressure of the molecules on the container, V is

the volume of the container, and k is a constant. The value of k

always stays the same so that P and V vary appropriately. For

example, if pressure increases, k must remains constant and

thus volume will decrease. This is consistent with the

predictions of Boyle's law.

Reference 2

EQUIPMENT and COMPONENTS USED:

(1) Tank 1 for isothermal change of state,

(2) Digital displays,

(3) 5/2-way valve for switching between compression and expansion,

(4) Heating controller,

(5) Digital display,

(6) Tank 2 for isochoric change of state

Method:

switch on unit master switch (4)

open the air discharge valve (1) on the lid of

the cylinder place both 3-way valves (3) in

position 2 switch on compressor using switch

until the liquid level has reached the lowest

mark (2) on the scale on the vessel.

switch off compressor close discharge valve

on the lid of the cylinder!

start data acquisition program and make the

corresponding settings switch on compressor

at the latest at

liter residual

volume for the

air enclosed

,switch off the

compressor

open graph

measured

valued and

interpret leave

pressure

cylinder

uncharged and continue immediately with the

compression experiment

Discussion the pressure would be a third of what it was before in Boyle's Law , Why does

this change?

The motion of gases also causes them to expand and fill their container, giving them a

volume equal to that of their container. If they did not strike the sides of the

container, they would continue on in a straight path.

Why are pressure and volume related then? Aren't they just two unique properties of

gases?

The link comes in how pressure is defined, and how volume affects the pressure.

Pressure is a derived unit. Pressure is force divided by a two-dimensional surface

measurement. Force is often measured in newtons (N), a unit derived from a

kilogram-meter (kg-m). Surface area is often measured in square meters or square

centimeters. A pressure unit would then be a newton per square meter (N/m2), the

Pascal (Pa). Because a Pascal is relatively small, force is often measured more

conveniently in kiloPascals (kPa).

With a gas, the pressure is exerted on the sides of the container. If there is a greater

surface area, the force will remain the same, so the pressure will go down. For

example, if a ten newton force is exerted over ten square meters, the pressure is 1

kPa. If the surface area increases to twenty square meters, the pressure is reduced to

0.5 kPa. If the surface area decreases to five square meters, the pressure is increased

to 2 kPa.

The volume of the container dictates its internal surface area for the gas. If the

volume of a gas decreases, because a gas expands to fill its container, the container's

volume must have decreased. Therefore, there is a smaller surface area, and the

pressure increases. If the volume of the gas expands, meaning a larger container, the

pressure would go down. This type of relationship is called an inverse relationship.

That's most of Boyle's law! Mathematically, this is represented as PV. Boyle's law

produces a constant, K, so extended, the formula is PV=K. However, because the

constant stays the same, additional pressures and volumes can be equated and

solutions can be found for unknowns. This equation can be a powerful tool in

solving for or converting pressures and volumes.

Reference 3

References :-

Reference 1

http://chemistry.bd.psu.edu/jircitano/gases.html

Reference 2

Diving.html-Scuba-And-Law-http://scuba.about.com/od/Theory/p/Boyles

Reference 3

http://library.thinkquest.org/12596/boyles.html

others from laboratory book (applied heat laboratory manual )