Boyle’s Law
What are the 4 variables that
describe a gas phase system?
•
•
•
•
Volume
Temperature
Pressure
Amount of gas (in moles)
Fixed Mass?
• You don’t change the number of moles
of gas. That is…
BOYLE - 1662
Temperature and Amount are constant.
Look at relationship between P and V.
What happened when I increased the
pressure on the syringe?
As pressure increases, volume decreases.
Image From Tiger
Boyle’s Law: 4 step
J-Tube experiments
Pressure (atm)
Volume (cm3)
1
1.00
800
2
2.00
400
3
3.00
267
4
4.00
200
Trial
Inverse Relationships
• Graph of two variables is a ...
• Properties:
– Relationship is inverse.
– Product of the two variables is a constant.
Scientists plot data because
a picture shows relationships
better than lists of numbers.
There are lots of “pictures”
that scientists &
mathematicians recognize.
Trial
Pressure
(atm)
Volume
(cm3)
PressureVolume
(atm-cm3)
1
1.00
800
800
2
2.00
400
800
3
3.00
267
800
4
4.00
200
800
For a given T and amount, pressure X volume
always equals the same number – the product is
CONSTANT!
Comparison
Pressure
Change
Volume
Change
Trials 1 & 2
1 to 2
800 to 400
2 to 1
Trials 1 & 3
1 to 3
800 to 267
3 to 1
Trials 1 & 4
1 to 4
800 to 200
4 to 1
Boyle’s Law - words
• The volume of a sample of
gas is inversely proportional
to its pressure, at constant
temperature.
Boyle’s Law - mathematically
P x V = k (constant)
V = k/P or P = k/V
P1V1 = P2V2
For every point on the hyperbola,
P x V = the same constant, k