•Sections 1 & 2
Section 13.1 The Gas Laws
• State the relationships among pressure, temperature,
and volume of a constant amount of gas.
• Apply the gas laws to problems involving the
pressure, temperature, and volume of a constant
amount of gas.
scientific law: describes a relationship in nature that
is supported by many experiments
Explain the difference between a law & a theory?
Section 13.1 The Gas Laws (cont.)
Boyle’s law
absolute zero
Charles’s law
Gay-Lussac’s law
combined gas law
For a fixed amount of gas, a change in
one variable—pressure, temperature,
or volume—affects the other two.
What is a variable?
Boyle's Law
• Boyle’s law states that the volume of a fixed
amount of gas held at a constant temperature
varies inversely with the pressure.
P1V1 = P2V2 where P = pressure and V = volume
Give an everyday example of Boyle’s Law.
Charles's Law
• As temperature increases, so does the
volume of gas when the amount of gas and
pressure do not change.
• Kinetic-molecular theory explains this
property.
Draw a series of cartoons to show what happens to a filled helium
balloon as the temperature gradually increases.
Charles's Law (cont.)
What type of mathematical relationship is V vs T ?
Charles's Law (cont.)
• Absolute zero is zero on the Kelvin scale.
• Charles’s law states that the volume of a
given amount of gas is directly proportional to
its kelvin temperature at constant pressure.
Why must all temperatures be put into Kelvin units when using gas laws?
Gay-Lussac's Law
• Gay-Lussac’s law states that the pressure
of a fixed amount of gas varies directly with
the kelvin temperature when the volume
remains constant.
How does Gay-Lussac’s Law apply to NASCAR racing teams?
Gay-Lussac's Law (cont.)
What type of mathematical relationship is P vs T ?
The Combined Gas Law
• If all three laws (Boyle’s, Charles’, GayLussac’s) are combined then the resulting
equation is the:
• combined gas law
states the relationship among
pressure, temperature, and
volume of a fixed amount of
gas.
In the combined gas law formula, draw a circle around Boyles’ Law, Charles’ Law & GayLussac’s Law. Shade in each circle a different color to distinguish the individual laws that make
up the combined law.
The Combined Gas Law (cont.)
When using the combined gas law, cross
out any unnecessary variable.
•Ex) A child’s party inflatable has a pressure of
15.8 atm at the beginning of the party
when the temperature is 33oC. Near the
end of the party the temperature drops to
17oC. What is the new pressure?
Solution:
1st: Convert Celsius temperatures to Kelvin units.
T1 = 33 + 273 = 306 K
T2 = 17 + 273 = 290. K
The Combined Gas Law (cont.)
2nd: Substitute values into equation.
15.8 atm V1
306 K
=
P2 V2
290. K
3rd: Cross out any variables not mentioned at all.
4th: Cross multiply & solve for the unknown.
(15.8atm) (290. K) =
306 K
(306 K) P2
306 K
P2 = 15.0 atm
The Combined Gas Law (cont.)