1. Use of Boyle’s lawUse of Boyle’s law
apparatus to verify Boyle’sapparatus to verify Boyle’s
law and to measure thelaw and to measure the
pressure of the atmospherepressure of the atmosphere
Experiment number (3Experiment number (3((

2. Atmospheric PressureAtmospheric Pressure
Atmospheric pressureAtmospheric pressure
is the pressure exertedis the pressure exerted
by a column of air fromby a column of air from
the top of thethe top of the
atmosphere to theatmosphere to the
surface of the Earth.surface of the Earth.

3. Atmospheric PressureAtmospheric Pressure
1 atm = 760 mm Hg
The atmosphere begins at
Earth’s surface and extends
upwards. The boundary where
it ends and outer space begins
is not clearly defined, so one
method used to determine this
is pressure changes.
Atmospheric pressure is simply
the weight of the air above. At
sea level, atmospheric
pressure is a weight over 1 kg
per square cm. The
atmospheric pressure
decreases the higher up one
goes.

4. Boyle’s LawBoyle’s Law
Boyle’s LawBoyle’s Law statesstates
thatthat
• The pressure of a gasThe pressure of a gas
is inversely related tois inversely related to
its volume when T andits volume when T and
n are constant.n are constant.
• If volume decreases,If volume decreases,
the pressurethe pressure
increases.increases.
P
V

5. ApparatusApparatus
A glass tube AB of uniform
bore about 10 mm in
diameter and closed at
one end. The other end is
connected by rubber
tubing to a glass tube CD.
When mercury is poured
into the limb CD some air
trapped in the closed limb
AB, ruler (1000 mm)
A
X
C
Y
DB
L
H
Rubber

6. MethodMethod
Lower the tube AB as much as
possible and raise the tube
CD until the mercury level X
and Y are visible, record the
scale readings of these levels
and also the scale reading of
A, the inside of the closed end
of the tube AB. Alter the
pressure by suitable
adjustment of both limbs of the
apparatus and take about ten
sets of readings over the
largest ranges of pressure and
volume of which the apparatus
is capable.
A
X
C
DB
L
Rubber
Y
Move up
ward,
increase
5mm for x
Then Move
down ward,
decrease
5mm for x

7. Scale readings / mmScale readings / mm
AA XX YY A-X=LA-X=L Y-X=HY-X=H 11//LL
695695 604604 639639 9191 3535 0.01100.0110
695695 599599 599599 9696 00 0.01040.0104
695695 594594 547547 101101 --4747 0.01000.0100
1
H = K X ------ - B
L
Where K is constant and equal to slope,
ON = B (atmospheric pressure).
H (mm)
1/L (mm-1
)
O
N

8. Set your report as the following:Set your report as the following:
1. Title.
2. Apparatus.
3. Medical applications (try to use internet)
4. Data table.
5. Graph.
6. Calculation.
7. Discussion.
Note: put answers of these questions in your discussion.
• Atmospheric pressure is less than 760 mmHg, because our place is over sea
level. Write theoretical atmospheric pressure for ERBIL, and then discuss the
different with your experimental value.
• What happened if we use water instead of mercury for determination of the
atmospheric pressure?
• Under sea level is the pressure increase or decrease?