Lecture_06OCT

# Lecture_06OCT - The Gaseous State of Matter i.e gases...

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Unformatted text preview: The Gaseous State of Matter ( i.e., gases) Properties of solids, liquids and gases solid • definite shape • definite volume liquid • indefinite shape takes shape of container • definite volume gas • indefinite shape takes shape of container • indefinite volume fills volume of container Properties of solids, liquids and gases solid • atoms/molecules are tightly packed • strong attractive f o r c e s b e t w e e n atoms/molecules liquid • atoms/molecules are in close contact • attractive forces between atoms/molecules BUT atoms/molecules can move freely gas • atoms/molecules have overcome attractive forces • atoms/molecules are relatively far apart and move independently Kinetic Molecular Theory General theory to explain the behavior and properties of gasses Assumptions 1. Gases consist of tiny particles 2. Distance between gas particles is large compared to size of particles ( i.e., most of gas volume is empty space) 3. Gas particles have no attraction for one another 4. Gas particles move in straight lines in all directions, colliding frequently with one another and the walls of the container 5. No energy is lost during collisions 6. The average kinetic energy of gas particles is the same for all gases at the same temperature An ideal gas behaves exactly as specified by the theory No truly ideal gases exist, but many real gases approach ideal behavior at non-extreme temperatures and pressures Four inter-related variables used to describe a system in the gas state • Pressure ( P ) • Temperature ( T ) • Volume ( V ) • Number of moles ( n ) Pressure: General defnition Pressure is defned as force per unit area : Pressure = Force Area This can be any type of force -- gravitational, electrostatic, mechanical, hydraulic, etc. • The greater the Force , the greater the pressure • The larger the area over which the Force is applied, the lower the pressure Example : This is how snowshoes work ¡orce = weight ¡orce = weight Area: (small) Area: (large) Snow surface Pressure of gases • the pressure exerted by a gas results from collisions of gas molecules with the surface The SI units for pressure are Newtons per square meter ( N / m 2 ) [ 1 Pascal (Pa) = 1 N / m 2 ] • but it is often more convenient to express gas pressure in units related to atmospheric pressure Pressure is defned as force per unit area : Gases exert pressure on any surface with which they are in contact Atmospheric pressure Average composition of dry air ( i.e., no water vapor) Percent Gas (by volume) Nitrogen 78.08 % Oxygen 20.95 % Argon 0.93 % Carbon dioxide 0.033 % Neon 0.0018 % Helium 0.0005 % Methane 0.0002 % Krypton 0.0001 % 1 m 2 column oF air (mass = 10,339 kg) PRESSURE UNIT: 1 atmosphere = 101,325 N/m 2 1 atm pressure at surFace Gravitational Force Weight = 10,339 kg x 9.8 m/s 2 = 101,325 N Atmospheric pressure...
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Lecture_06OCT - The Gaseous State of Matter i.e gases...

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