Transcript The Gas Laws - Warren Township Schools

The Gas Laws
Gases have properties
which we can observe
with our senses
These properties include: pressure
(p), temperature, mass, and the
volume (V) which contains the
gas.
Gas in a Balloon
• Gas molecules inside
a volume (a balloon)
are constantly
moving around freely.
• During this
molecular motion
they frequently
collide with each
other and with the
surface of any
enclosure there may
be (in a small balloon
there are many
billions of collisions
each second).
Factors that Affect
Gas Pressure
• What changes might affect the
pressure of a gas in a
container?
• Temperature
• Volume
• Number of particles
Chapter 3
Section 2 Behavior of Gases
Describing Gas Behavior
• Temperature Temperature is a measure of how fast
the particles in an object are moving.The faster the
particles are moving, the more energy they have.
• Volume Volume is the amount of space that an
object takes up. Because gas particles spread out, the
volume of any gas depends on the container that the
gas is in.
Chapter 3
Section 2 Behavior of Gases
Describing Gas Behavior, continued
• Pressure The amount of force exerted on a given
area of surface is called pressure. 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
• Reducing the volume of a gas
increases its pressure if the
temperature of the gas and the
number of particles are
constant
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 is the action
of a 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.
• The bubbles exhaled by a scuba
diver grow as the approach the
surface of the ocean.
• Deep sea fish die when brought
to the surface.
• Pushing in the plunger of a
plugged-up syringe decreases
the volume of air trapped under
the plunger.
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.
Temperature Pressure
Relationship
• The pressure of a gas increases
if the temperature increases.
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.
• 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.smm.org/heart/lungs/
breathing.htm