Transcript The Gas Laws - Warren Township Schools

The Gas Laws
Properties of Gases
•
•
•
•
Occupy space
Have mass
No definite shape or volume
Unconfined gases expand
indefinitely
• Have low density
Gas in a Balloon
• Gas molecules inside
the balloon are
constantly moving
around freely.
• They collide with
each other and with
the surface of the
balloon
• in a small balloon
there are many
billions of collisions
each second!
What factors affect
Gas Pressure?
• Temperature
• Volume
• Number of particles
Chapter 3
Temperature
•Temperature: a measure of how fast the particles in
an object are moving.
•The faster the particles move, the more energy they
must have.
Volume
• Volume: the amount of space that an
object takes up.
• The volume of any gas depends on the
container that the gas is in.
Chapter 3
of
G
a
s
e
s
Pressure
• Pressure: amount of force exerted on a
given area of surface
•You can think of pressure as the number of
times the particles of a gas hit the inside of
their container.
Robert Boyle investigated
the relationship between the
volume of a gas and its
pressure
Volume and Pressure
Relationship
• Volume and pressure are
inversely related
• If I reduce the volume of the
container, I increase the
pressure of the gas
Volume vs
Pressure
• When he
changed the
pressure the
volume
responded in
the opposite
direction.
Boyle’s Law
• Boyle’s Law states that the
volume of a gas is inversely
proportional to its pressure if
the temperature and the number
of particles are constant.
A practical application of
Boyle’s Law: syringe
• When fluids are drawn into
a syringe, the volume
inside the syringe is
increased.
• the pressure decreases on
the inside
• the pressure on the
outside of the syringe is
greater
• Fluids are forced into the
syringe.
• pushing the plunger in decreases the
volume on the inside
• increases the pressure inside and
makes it greater than outside
• fluids are forced out.
• http://revver.com/video/821971/imagin
ationland-creatures-in-a-vacuumeaster-demo/
Other example of Boyle’s Law
• bubbles exhaled by a scuba
diver grow as the approach the
surface of the ocean.
• Deep sea fish explode when
brought to the surface rapidly.
Charles’ Law
• Doubling the temperature of a
gas doubles its volume, as long
as the pressure of the gas and
the amount of gas isn't
changed.
• http://education.jlab.org/frost/bal
loon.html
Temperature Pressure
Relationship
• There is a direct relationship
between the pressure of the gas
and the temperature of the gas
• The pressure of a gas increases
as the temperature increases.
• As the temperature decreases,
the pressure decreases.
Why does gas pressure
increase when the
temperature increases?
• The particles in a gas are moving.
They bump into the walls creating
a pressure.
• When a gas is heated, its particles
speed up.
There are two ways that
this increases the
pressure:
•the faster particles bump into the
container walls more often
•each collision is harder because the
particles are moving faster.
Examples of Charles’ Law
• A football inflated inside and then taken
outdoors on a winter day shrinks slightly.
• A slightly underinflated rubber life raft left in
bright sunlight swells up
• The plunger on a turkey syringe thermometer
pops out when the turkey is done
Gas Behavior Laws
• Boyle’s Law Boyle’s law states that for a fixed
amount of gas at a constant temperature, the volume
of the gas is inversely related to pressure.
P1V1 = P2V2
• Charles’s Law Charles’s law states that for a fixed
amount of gas at a constant pressure, the volume of
the gas changes in the same way that the temperature
of the gas changes.
T1V2 = T2V1
Chapter 3
Section 2 Behavior of Gases
• http://www.chem.iastate.edu/group/G
reenbowe/sections/projectfolder/flas
hfiles/gaslaw/boyles_law_graph.html
• http://www.jersey.uoregon.edu/vlab/P
iston
• http://www.grc.nasa.gov/WW/K12/airplane/Animation/frglab2.html
The Combined Gas Law
• Combination of Boyle’s and
Charles’ laws
• The volume of gas is directly
proportional to the temperature
and inversely proportional to
the pressure.
• P1V1
T1
P2V2
=
T2
How You Breathe
• Your lungs are are
made of spongy,
elastic tissue that
stretches and
constricts as you
breathe.
• The airways that
bring air into the
lungs are made of
smooth muscle and
cartilage, allowing
the airways to
constrict and
expand.
• What we need is a way to
create air pressure to draw the
air into our bodies.
• Atmospheric pressure is about
760 mm Hg.
• Since the flow is always from an
higher to lower, we have to be
able to make our respiratory
tract have a lower pressure
than 760 mm Hg.
• How can we decrease the
pressure within our respiratory
tract?
This is the trick.
•
In order to decrease the
pressure within our respiratory
tract, we have to expand our
container, our chest. If we can
expand our chest, the air
pressure within will fall, and air
will rush into our respiratory
tract.
Inhaling
• When you
inhale, the
diaphragm and
the muscles
between your
ribs contract
and expand the
chest cavity.
• This expansion lowers the
pressure in the chest cavity
below the outside air pressure.
Air then flows in through the
airways (from high pressure to
low pressure) and inflates the
lungs.
Inhalation and exhalation
• When you exhale, the diaphragm and
rib muscles relax and the chest
cavity gets smaller.
• The decrease in volume of the cavity
increases the pressure in the chest
cavity above the outside air
pressure.
• Air from the lungs (high pressure)
then flows out of the airways to the
outside air (low pressure). The cycle
then repeats with each breath.
• http://www.youtube.com/watch?
v=n5bsQ_YDYCI