THE GAS LAWS Section 4.1 pg. 150 160 Homework: Boyles Law: pg.
152 # 6-9 Charles Law: pg. 156 # 14-17 Combined Gas Law: pg. 159 #
20-23
Slide 2
Gas Laws They are based on the temperature, pressure and volume
relationships that all gases have in common 1. Boyles Law P 1 V 1 =
P 2 V 2 2. Charles Law V 1 = V 2 T 1 = T 2 3. Combined Gas Law P 1
V 1 =P 2 V 2 T 1 = T 2
Slide 3
Boyles Law Anglo- Irish chemist Robert Boyle (1627-1691) was a
founding member of the Royal Society of London.
Slide 4
Boyles Law Considers the effects of pressure on the volume of a
gas only while temperature is held constant This is an inverse
relationship: P = V P = V Boyles Law states: as the pressure on a
gas increases, the volume of the gas decreases proportionally if
temperature and mass are constant Boyles Equation: P 1 V 1 = P 2 V
2
Slide 5
Boyles Law As the pressure on a gas increases, the volume of
the gas decreases proportionally if temperature and mass are
constant
Demos Cartesian Diver DemoDiver The Cartesian diver is named
after the French philosopher, Rene Descartes (1596-1650), and is a
very old experiment. The volume of a gas decreases as the pressure
on the gas increases. As you squeeze the bottle, the pressure is
transferred from your hand to the water and from the water to the
air trapped inside the diver. As the volume of air in the diver
gets smaller, more water enters the diver, making it heavier and
less buoyant, and the diver sinks to the bottom. As the pressure is
released, the air inside the diver expands and increases the
buoyancy so that the diver rises. Expanding Marshmallow
DemoMarshmallow Demo The marshmallow expands as the volume in the
syringe increases and the pressure decreases. It shrinks as the
volume is reduced and the pressure is increased
Slide 8
Boyles Law - PRACTICE 1. A sample of gas at 1.0 atm is in a 1.0
L container. What is the pressure when the volume is changed to
2.0L? (Assume T and m are constant) P 1 V 1 = P 2 V 2 (1.0 atm)
(1.0 L) = (x) (2.0 L) 1.0 atmL = 2.0 L (x) 2.0L 2.0L 0.50 atm = P 2
According to Boyles Law, the gas would now have a pressure of 0.50
atm
Slide 9
Boyles Law - PRACTICE 2. A 2.0 L party balloon at 98 kPa is
taken to the top of a mountain where the pressure is 75 kPa. Assume
that the temperature and mass of the gas remain the same. What is
the new volume of the balloon. P 1 V 1 = P 2 V 2 (98 kPa) (2.0 L) =
(75 kPa) (x) 196 kPaL = 75 kPa (x) 75 kPa 75 kPa 2.6 L = V 2
According to Boyles Law, the balloon would have a new volume of
2.6L
Slide 10
Practice Pg. 152 #6-9
Slide 11
Charles Law Jacque Charles (1746- 1823) He made the first
flight of a hydrogen balloon on August 27, 1783. This balloon was
destroyed by terrified peasants when it landed outside of
Paris.
Slide 12
Charles Law Shows the relationship between temperature (must be
in Kelvin) and volume of gas if pressure and mass are constant This
is a direct relationship: T = VT = V Charles Law states: as the
temperature of a gas increases, the volume increases
proportionally, provided that the pressure and mass remain constant
Charles Equation : V 1 = V 2 T 1 = T 2
Slide 13
Charles Law As the temperature of a gas increases, the volume
increases proportionally, provided that the pressure and mass
remain constant
Slide 14
Charles Law - Graphically When the graphs of several careful
volume-temperature experiments are extrapolated, all the lines meet
at absolute zero, 0K or -273 C
Slide 15
Demos Pop Can demo Charles Law at work
Slide 16
Charles Law - PRACTICE 1. A gas inside a cylinder with a
movable piston is heated to 315C. The initial volume of gas in the
cylinder is 0.30 L at 25C. What will be the final volume when the
temperature is 315C? T 1 = (25 + 273) = 298K T 2 = (315 + 273) =
588K * Remember temperature has to be in Kelvin V 2 = V 1 T 2 T 1 =
(0.30 L)(588K) 298K = 0.59 L V 1 = V 2 T 1 = T 2 According to
Charles Law, the final volume will be 0.59 L
Slide 17
Practice pg. 156 #14 - 17
Slide 18
The Combined Gas Law Combined Gas Law You can get Boyles Law
back by assuming temperature is constant. You can get Charles Law
back by assuming pressure is constant
Slide 19
The Combined Gas Law When Boyles and Charles laws are combined,
the resulting combined gas law produces a relationship among the
volume, temperature, and pressure of any fixed mass of gas. The
combined gas law is a useful starting point for all cases with
gases, even if one of the variables is a constant. A variable that
is constant can easily be eliminated from the combined gas law
equation, reducing it back to Boyles or Charles Law
Slide 20
Combined Gas Law - Practice 1. A gas cylinder with a fixed
volume contains a gas at a pressure of 652 kPa and a temperature of
25C. If the cylinder is heated to 150C, use the combined gas law to
calculate the new pressure. Because volume is constant we can
cancel V 1 and V 2 because V 1 = V 2 T1 = (25 + 273) = 298 K T2 =
(150 + 273) = 423 K P 1 V 1 = P 2 V 2 T 1 = T 2 P 2 = P 1 T 2 T 1 P
2 = (652kPa) (423K) 298 K P 2 = 925 kPa The gas will have a new
pressure of 925 kPa
Slide 21
Combined Gas Law - Practice 2. A balloon containing helium gas
at 20 C and a pressure of 100 kPa has a volume of 7.50 L. Calculate
the volume of the balloon after it rises 10 km into the upper
atmosphere, where the temperature is 36 C and the outside air
pressure is 28 kPa. (Assume that no gas escapes and that the
balloon is free to expand so that the gas pressure within it
remains equal to the air pressure outside.) T1 = (20 + 273) = 293 K
T2 = (-36 + 273) = 237 K P 1 V 1 = P 2 V 2 T 1 = T 2 V 2 = P 1 V 1
T 2 T 1 P 2 V 2 = (100kPa)(7.50 L)(237 K) (293 K)(28 kPa) V 2 =
21.6 L = 22 L According to the Combined Gas law, the volume of the
balloon in the upper atmosphere will be 22L
Slide 22
SUMMARY STP: 0 C and 101.325 kPa (exact values) SATP: 25 C and
100 kPa (exact values) 101.325 kPa = 1 atm = 760 mm Hg (exact
values) absolute zero = 0 K or 273.15 C K = (C) + 273 (for
calculation) Boyles Law P 1 V 1 = P 2 V 2 Charles Law V 1 = V 2 T 1
= T 2 Combined Gas Law P 1 V 1 = P 2 V 2 T 1 = T 2
Slide 23
Practice Pg. 159 # 20 - 23
Slide 24
Homework Boyles Law: pg. 152 # 6-9 Charles Law: pg. 156 # 14-17
Combined Gas Law: pg. 159 # 20 23 Gas Laws Worksheets Pg 161 Q 1-7
QUIZ WEDNESDAY
