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Collisions of Gas Particles

Collisions of Gas Particles. Collisions of Gas Particles. Kinetic Theory. Kinetic Molecular Theory. Postulates of the Kinetic Molecular Theory of Gases. Gases consist of tiny particles (atoms or molecules) These particles are so small, compared with the distances between

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Collisions of Gas Particles

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  1. Collisions of Gas Particles

  2. Collisions of Gas Particles

  3. Kinetic Theory

  4. Kinetic Molecular Theory Postulates of the Kinetic Molecular Theory of Gases • Gases consist of tiny particles (atoms or molecules) • These particles are so small, compared with the distances between • them, that the volume (size) of the individual particles can be assumed • to be negligible (zero). • 3. The particles are in constant random motion, colliding with the walls of • the container. These collisions with the walls cause the pressure exerted • by the gas. • 4. The particles are assumed not to attract or to repel each other. • 5. The average kinetic energy of the gas particles is directly proportional • to the Kelvin temperature of the gas

  5. AS TEMP. , KE Kinetic Molecular Theory (KMT) • explains why gases behave as they do • deals w/“ideal” gas particles… 1. …are so small that they are assumed to have zero volume • …are in constant, straight-line motion • …experience elastic collisionsin which no energy is lost • …have no attractive or repulsiveforces toward each other • …have an average kinetic energy (KE)that is proportional • to theabsolute temp. of gas (i.e., Kelvin temp.)

  6. Elastic vs. Inelastic Collisions 8 3

  7. 8 8 Elastic vs. Inelastic Collisions POW v1 v2 elastic collision v3 v4 inelastic collision

  8. 8 8 Elastic Collision v1 before v2 after

  9. All collisions must be elastic Take one step per beat of the metronome Container Class stands outside tape box Higher temperature Faster beats of metronome Decreased volume Divide box in half More Moles More students are inside box Mark area of container with tape on ground. Add only a few molecules of inert gas Increase temperature Decrease volume Add more gas Effect of diffusion Effect of effusion (opening size) Model Gas Behavior

  10. 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. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  11. many different molecular speeds molecules sorted by speed Molecular Velocities Fractions of particles the Maxwell speed distribution speed http://antoine.frostburg.edu/chem/senese/101/gases/slides/sld016.htm

  12. Real Gases • Particles in a REAL gas… • have their own volume • attract each other • Gas behavior is most ideal… • at low pressures • at high temperatures • in nonpolar atoms/molecules Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  13. 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 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  14. Characteristics of Gases • Gases can be compressed. • no volume = lots of empty space • Gases undergo diffusion & effusion. • random motion Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  15. Properties of Gases V = volume of the gas (liters, L) T = temperature (Kelvin, K) P = pressure (atmospheres, atm) n = amount (moles, mol) Gas properties can be modeled using math. Model depends on:

  16. PT V P T V PT V 1 V Boyle’s P a ___ a Charles V T a Gay-Lussac’s P T Pressure - Temperature - Volume Relationship

  17. P T V P n V 1 V Boyle’s P a ___ a Charles V T a Gay-Lussac’s P T Pressure - Temperature - Volume Relationship

  18. Pressure and Balloons B When balloon is being filled: PA > PB A When balloon is filled and tied: PA = PB When balloon deflates: PA < PB A = pressure exerted BY balloon B = pressure exerted ON balloon

  19. A B C Balloon Riddle When the balloons are untied, will the large balloon (A) inflate the small balloon (B); will they end up the same size or will the small balloon inflate the large balloon? Why?

  20. 10 10 10 10 Kinetic Theory and the Gas Laws (a) (b) (c) increased temperature increased pressure original volume original temperature original pressure original volume increased temperature original pressure increased volume Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 323 (newer book)

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