Lesson 4.4

The Gas Laws, part 2 Temperature, Pressure, and Charles’ Law

I. SI Temperature •  0 K is absolute zero •  You can’t get colder because the molecules

stop moving. •  Conversion factors: •  K = °C + 273.15 •  °C = 5/9 (°F – 32) •  °F = 9/5 (°C) + 32

I. SI Temperature •  Comparison…

II. STP •  STP stands for standard temperature and

pressure. •  It is a reference point that chemists use to

make measurements of a gas (volume, density, vapor pressure, etc.)

•  Standard Temperature: 0°C (273 K) •  Standard Pressure: 1 atm (760 torr)

II. STP •  Molar Volume of a Gas •  All gases have volume of 22.4 L at STP. •  This is true for every gas no matter the molar

mass.

III. Charles’ Law •  Liquid nitrogen has a boiling temperature of

-196°C. •  If you put an inflated balloon in liquid nitrogen it

shrinks.

III. Charles’ Law •  The volume and temperature of a gas are

directly proportional. •  Equations: •  V = kT or V = k

T

€

V1T1

=V2T2

T must be in Kelvin!

III. Charles’ Law •  Practice: A sample of neon gas occupies a

volume of 752 mL at 25°C. What volume will the gas occupy at 50°C if the pressure remains constant?

•  Answer: 815 mL