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BEHAVIOR
OF GASES
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PRESSURE
The amount offorce exerted
per unit area
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A
F
P!
Pressure = force / area
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A
FP!
Unit on pressure is PASCAL (Pa)
PASCAL = Newton / meter2
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The atmosphere on Earth
exerts pressure oneverything.
How much pressure?
About 100,000P
a!!!(~100kPa)
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This means that in every square
meter, 100,000N of pressure is
exerted.
100,000N = weight of a large truck
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As you move farther from the earth,
the pressure becomes MUCH less.
Which
layer wouldhave the
least
pressure?Why?
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Pressure dependson how often the
particles hit the
surfaceMore times = more pressure
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Characteristics of Gases
Negligible Volume (verycompressible)
Gases are in constant motion Collisions are completely elastic
No forces off attraction or repulsion
Kinetic energy of a gas is directlyproportional to the temperature
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BOYLES LAWFor a given amount of gas
at a constant temperature
the volume of the gasvaries inversely with
pressure.
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CHARLESS LAW
Volume of a gasincreases if the
temperature increases(pressure staying constant)
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How could Charless
Law be used to
explain why hot airballoons fill up.
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If temperature is constant
when
V decreasesthen
P _________INCREASES
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If pressure is constant
when
T increasesthen
V _________INCREASES
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What happens
when you relax in
a swimming pool?
You float!!!Duhbut why?
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BUOYANCY
The ability of a liquidor gas to push up on
an object placed in it
(you in a swimming pool)
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If the buoyant forceis greater than the
weight, then object
FLOATS!If notit sinks.
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DENSITY
The relationship of themass (weight) to how
much space it takes up
(volume)
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v
m
D!
volume
massDensity !
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ARCHIMEDES
PRINCIPLE
The buoyant force onan object in a fluid is
equal the weight of the
fluid displaced
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