Gases Notes
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All gases share some physical properties:
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These properties combine to describe the behavior of gases using the “gas laws”
Pressure
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Pressure is the amount of force per given amount of area (P=F/area)
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________________ forces exert greater ________________________
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When the area over which the pressure is exerted is __________________, the pressure is _________________
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Why is there more pressure on you the deeper you move in a body of water?
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Why is it harder to breathe when you’re up in a mountain?
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Atmospheric pressure
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The pressure exerted by the _____________________ on the earth
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______________________________ as you move up
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About _____________________+ (pounds per square inch) at sea level
Standard pressure
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“normal” atmospheric pressure at sea level
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Standard Pressure:
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Barometer
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Manometer
Kinetic Molecular Theory
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A set of ideas (__________________) used to describe and explain the ___________________ of gases
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Any gas that behaves exactly in this manner is called an “____________ ______________”
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There are not any “ideal gases” in real life. _____________ ______________ behave much like “ideal” gases
unless they are under high ____________ and ________________.
Point 1
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Gases are composed of tiny particles called _______________
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Molecules are so far apart that gases are mostly _________ _______________
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Because of this, gases can be easily compressed and mixed
Point 2
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Gas molecules posses _______________ ________________
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Gas molecules are in
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Pressure is…
Point 3
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Collisions between gas molecules and each other or the container are ___________________
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No ______________ ______________ is changed into another form of energy (like heat)
The pressure of an enclosed gas will _____________ change unless its temperature or volume _____________
Point 4
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Molecules of a gas are not
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They move ____________________________ of each other
Point 5
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Individual molecules of a gas are moving at different speeds because they have different ___________ ________
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The average kinetic energy (__________) is ____________ ____________________ to the temperature of a gas
Boyles Law
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Pressure and volume are inversely related at a constant temperature and number of moles
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Conceptual:
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Relationship:
Temperature
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Absolute temperature is measured in _________________ (K)
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0 K is
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K = °C + 273
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°C = K – 273
Standard temperature: 273 K
Charles’ Law
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Volume and temperature are ______________ related when ___________ and number of moles is constant
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Conceptual:
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Relationship:
Gay-Lussac’s Law
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Conceptual:
Combined Gas Law
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A combination of Boyle’s, Charles’, and Gay-Lussac’s Laws, where
P1V 1 P 2V 2
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T1
T2
Avogadros Hypothesis
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Equal volumes of gases contain an equal ______________ of __________ (n) when compared at the same
_____________ and ____________
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Molar volume of any gas:
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If P, V, and T are the same, then n is the same (constant)
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R=
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R=
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R=
PV
 nR or, PV  nRT
T
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What is the volume of 0.2 moles of a gas at STP? (measure pressure in kPa)
Molar mass
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When the mass of an ________________ mass is given, you can solve for _____________ ___________
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Number of moles (n) = mass (m)/Molar mass (Mm)
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Substituted into the ideal gas law:
Density
Since…
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n=
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Denisty
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The ideal gas law can be written so solve for density:
Dalton’s Law of Partial pressure
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The total ___________ of a mixture of gases is the sum of the partial pressures of the ______________ gases
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PT =
Effusion
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Effusion is the ___________ of gas molecules through an extremely tiny opening into a region of lower pressure
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Diffusion
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Diffusion is the tendency of molecules to move toward areas of lower concentration until the concentration is
uniform throughout the system
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Graham’s Law
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The rate of effusion (or diffusion) of a gas is inversely proportional to the square root of its molar mass (at
constant T and P).
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