Koya University Faulty of Engineering

School of Petroleum & Chemical Engineering

Chemical Engineering department

EXPERIMENT NUMBER TWO

BOYLES LOW

Thermodynamics Boyle's low

Instructor: Mr.Rebwar & Mr.Omer

Author Name: Aree Salah Tahir & shwan sarwan sadiq

Experiment Contacted on: 29/oct/2013

Report Submitted on: 12/nov /2013

List of content:

Abstract …………………………………….

Objectives…………………………………...

Introduction …………………………………

Background Theory ………………………...

Method ……………………………………...

Calculation…………………………………..

Equipment and components used……………

Discussion …………………………………...

References …………………………………...

Abstract:

Pressure and volume are inversely

proportional to Each other.

This means that as the pressure Decreases, the

volume increases, and as the pressure

Increases, the volume decreases. One way to

think Of this is if you push on a gas by

decreasing its Volume, it pushes back by

increasing its pressure.

This relationship is called Boyle’s Law and

makes up Part of the ideal gas law.

OBJECTIVES:

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.

References…(1)

Introduction:

Boyle's Law explains how the volume of a gas

varies with the surrounding pressure. Many

aspects of scuba diving physics become clear

once you understand this simple gas law.

Boyle's Law is:

PV = c

In this equation, “P” represents pressure, “V”

signifies volume and “c” represents a constant

(fixed) number.

If you are not a math person, this may sound

really confusing – don't despair! This equation

simply states that for a given gas (such as air

in a scuba diver's buoyancy compensator), if

you multiply the pressure surrounding a gas by

the volume of gas you will always end up with

the same number.

Because the answer to the equation can not

change (that's why it is called a constant), we

know that if we increase the pressure

surrounding a gas (P), the volume of the gas

(V) must get smaller. Conversely, if we

decrease the pressure surrounding a gas, the

volume of the gas will become greater. That's

it! That's Boyle's entire law.

Almost. The only other aspect of Boyle's Law

that you need to know is that the law only

applies at a constant temperature. If you

increase or decrease the temperature of a gas,

the equation doesn't work anymore.

References…(2)

BACKGROUND THEORY:

When the volume of a gas shrinks, the gas

molecules have less space to move around and

so they hit their

container more often. The more frequently the

gas impacts the container walls, the higher the

pressure.

So, as volume decreases, the pressure

increases. If the container expands, the

impacts are less frequent

and the pressure decreases.

This relationship can be described using

mathematics as well. Mathematically, Boyle’s

Law states that

PV = k

where k is any constant.

Boyle’s Law is important for both astronauts

and divers. Since the pressure in space is near

zero, space

suits have to be able to withstand the

expansion of the air that is within the suit

when the astronaut goes

outside. When divers are surfacing, they must

exhale. If they don’t, the air that is held in

their lungs will

expand and could rupture the lung tissue.

This experiment shows how the volume of the

air in whipped cream reacts to lowering

pressure.

References…(3)

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

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

References…(4)

Discussion:

How Does Boyle's Law Apply to Scuba Diving?:

Boyle's Law effects almost every aspect of scuba diving

because it describes the role of water pressure in the dive

environment. As a diver descends, the water pressure

around him increases, causing air in his scuba equipment

and body to occupy a smaller volume (compress). As he

ascends, water pressure decreases, so Boyle's Law states

that the air in his gear and body expand to occupy a

greater volume. Many of the safety rules and protocols in

scuba diving were created to help a diver compensate for

the compression and expansion of air due to changes in

water pressure.

Why does the pressure of a gas increase when the

volume of the container decreases?

Remember that the pressure of a gas on the walls of

the container is due to the collisions of the molecules on

the walls of the container. The change in momentum of

these molecules in unit time is a force exerted by the

walls of the vessel on the molecules, which, by Newton's

third law, exert an equal and opposite force on the walls

of the vessel. This force, divided by the area of the walls

in contact with the gas, is the pressure of the gas.

Why Is a Constant Temperature Necessary to Use

Boyle's Law?:

As mentioned above, Boyle's Law only applies to gases

at a constant temperature. Heating a gas causes it to

expand, and cooling a gas causes it to compress. A diver

can witness this phenomenon in action when he

submerges a warm scuba tank in cooler water. The

pressure gauge reading of a warm tank will drop when

the tank is submerged in cool water as the gas inside the

tank compresses.

What happens to an ideal gas in an infinite space

when the pressure is 0? Does the gas expand to

infinite volume?

Pressure will never be 0 in an infinite volume

hypothetical scenario because you have introduced a

gas. Regardless of how little you have added, there will

in always be that finite and measurable amount of gas

an infinite space. As volume increases, the pressure and

temperature will decrease. Subsequently, you should

expect the pressure to approach but never reach

absolute 0, and you should expect the temperate to

approach but never reach absolute 0

References:

1:

http://www.chm.davidson.edu/vce/gaslaws/boyleslaw.

html

2:

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

Diving.htm-Scuba

3:

http://littleshop.physics.colostate.edu/activities/atmos2

/PressureVolumeRelated

4:

http://www.gunt.de/static/s3438_1.php