Boyles law (compresion) (relation between pressure & volume)
Faulty of Engineering
School of Petroleum & Chemical Engineering
Chemical Engineering department
EXPERIMENT NUMBER TWO
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:
Background Theory ………………………...
Equipment and components used……………
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.
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.
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
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.
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
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
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
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
volume for the
,switch off the
uncharged and continue immediately with the
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
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
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
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
What happens to an ideal gas in an infinite space
when the pressure is 0? Does the gas expand to
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
always be that finite and measurable amount of gas in
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