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I. Physical Properties

12.1- Gases. I. Physical Properties. A. Kinetic Molecular Theory. kinetic-molecular theory: (def) theory of the energy of particles and the forces that act between them; based on idea that particles of matter are always in motion Kinetic molecular theory describes the motion of an ideal gas.

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I. Physical Properties

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  1. 12.1- Gases I. Physical Properties

  2. A. Kinetic Molecular Theory • kinetic-molecular theory:(def) theory of the energy of particles and the forces that act between them; based on idea that particles of matter are always in motion • Kinetic molecular theory describes the motion of an ideal gas

  3. A. Kinetic Molecular Theory • ideal gas: (def) imaginary gas that perfectly fits the assumptions of the kinetic-molecular theory

  4. A. Kinetic Molecular Theory • Particles in an ideal gas… • have no volume. • have elastic collisions. • are in constant, random, straight-line motion. • don’t attract or repel each other. • have an avg. KE directly related to Kelvin temperature.

  5. B. Real Gases • Particles in a REAL gas… • have their own volume • attract each other • proposed by van der Waals • Gas behavior is most ideal… • at low pressures • at high temperatures • in nonpolar atoms/molecules

  6. C. Characteristics of Gases • Gases expand to fill any container. • random motion, no attraction • Gases are fluids (like liquids). • no attraction • Gases have very low densities. • no volume = lots of empty space

  7. C. Characteristics of Gases • Gases can be compressed. • no volume = lots of empty space • Gases undergo diffusion & effusion. • random motion

  8. C. Characteristics of Gases • Diffusion: (def) process by which gases spontaneously spread out and mix with other gases; lighter gases diffuse more quickly • Effusion: (def) process by which gases particles under pressure pass through a tiny opening; lighter gases effuse faster

  9. A. Temperature K = ºC + 273.15 ºF -459 32 212 ºC -273 0 100 K 0 273 373 • Always use absolute temperature (Kelvin) when working with gases.

  10. B. Pressure SI unit of force is the Newton Which shoes create the most pressure?

  11. . Pressure Mercury Barometer • Barometer • measures atmospheric pressure - at sea level, height of column is 760 mm - P of Hg is equal to the P of the atmosphere

  12. E. Pressure U-tube Manometer • Manometer • measures contained gas pressure - difference in height of tubes indicates the gas pressure

  13. E. Pressure • KEY UNITS AT SEA LEVEL 101.325 kPa (kilopascal) 1 atm 760 mm Hg 760 torr 14.7 psi

  14. Pressure

  15. C. STP Standard Temperature & Pressure 0°C273.15 K 1 atm101.325 kPa -OR- STP

  16. D. Dalton’s law • Dalton’s law of partial pressure: • Ptotal = P1 + P2 + P3…+Pn (n = number of gases in mixture) **Total P exerted by collection gases is sum of pressure exerted by each gas

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