Gases and Boyle's Law
chapter 3 Lesson 2
Objective
you will be able to apply Boyle's Law
Review Properties of Gases
Fill their containers
Are compressible
Diffuse independently through
available space (miscible)
Volume and / or pressure
are affected by change in
temperature
Low viscosity: pour easily
Magnitude of force over a defined area is called
pressure.
According to the Kinetic Molecular Theory, gas
particle are in motion and colliding with the surface of
their containers. This creates the pressure
Manometers are used to measure gas pressure
Units of Pressure
The SI unit is the kilopascal, kPa.
kPa = 1000 N/m2
Standard atmospheric pressure is 101.325 kPa
Other measurements include atmospheres (atm),
mm of Hg and Bar
1 atm= 760 mm Hg = 101.325 kPa=1.013 bar
Convert
a) 3.0 atm to kPa b) 900 Bar to kPa
Since gases are affected by both temperature
and pressure it is often easiest to describe a lab
setting in terms of standard units.
STP - standard temperature and pressure is
1 atm (101.325 kPa) at 0º C
SATP - standard ambient temperature and
pressure is 100 kPa at 25º C (room conditions)
Notice the relationship?
P x V = constant ( k)
This is Boyleʼs Law k = PV
Since this constant remains the same for a given
gas we can predict how a sample of gas will
change when we change one of volume or
pressure.
P V =P V
1 1
2 2
A 200 mL sample of hydrogen gas is collected
when the pressure is 105 kPa. Over night the
pressure drops to 101kPa. What is the new
volume the gas occupies?
A volume of air is captured at a pressure of 1.2
atm. If the volume is reduced by a factor of
three, what will the new pressure be in mm of
Hg?
Assignment
Read text pages 109-111
Do practice problems p. 110 #1-6