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Kinetic Model of Matter

Kinetic Model of Matter. Textbook Chp 9 Pg 153-166. For this topic…. 80% is already covered in Chemistry. This is a quick revision This is a purely qualitative topic. There are no calculations. Topics. Solids, Liquids & Gases Brownian Motion Kinetic Model of Solids

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Kinetic Model of Matter

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  1. Kinetic Model of Matter Textbook Chp 9 Pg 153-166

  2. For this topic… • 80% is already covered in Chemistry. This is a quick revision • This is a purely qualitative topic. There are no calculations

  3. Topics • Solids, Liquids & Gases • Brownian Motion • Kinetic Model of Solids • Kinetic Model of Liquids • Kinetic Model of Gases • Gas Laws

  4. Properties of Solids, Liquids, Gases

  5. Brownian Motion • Robert Brown conducted an experiment by observing smoke particles under a microscope • Video: http://www.youtube.com/watch?v=cDcprgWiQEY • Smoke particles appeared to move in a random manner • “Brownian Motion” refers to the observed movement of particles in a fluid (liquid or gas)

  6. Brownian Motion • Brown explained his observations that the smoke particles are being randomly bombarded by air molecules • Common mistake: what is seen is NOT air molecules (which are too small to be seen) but smoke particles • Brownian motion provides evidence that air consists of tiny particles (molecules) moving in a random manner

  7. Kinetic Model of Matter • The Kinetic Model of Matter states that matter is made up of tiny particles(i.e. atoms and molecules) • These particles are always in continuous random motion

  8. Kinetic Model of Solids • Particles are closely packed together (lattice structure) • Large number of particles per unit volume (high density) • Particles vibrate about fixed positions • Particles held together by strong attractive forces between particles (strong inter-molecular bonds) • When solid is heated up, particles vibrate more vigorously • When enough energy is supplied, particles vibrate so strongly that strong attractive forces between particles are broken (melting to be become liquid)

  9. Kinetic Model of Liquids • Particles are randomly arranged • Particles are slightly further apart compared to solids (high density but less than solids) • Particles move around freely and randomly • While particles are not held at fixed positions, there are still strong attractive forces between particles (high inter-molecular forces) • When heated, particles move faster • When enough energy is supplied, particles move so quickly they break free from attractive forces and becomes isolated particles (boiling to become gas)

  10. Kinetic Model of Gases • Particles are randomly arranged • Particles are far apart from each other (negligible attractive forces between them) • Particles move randomly at fast speeds • Upon heating, particles move faster

  11. Kinetic Model of Gases • When a gas is held in a container, the collisions between the particles and the container give rise to gas pressure • 2 factors to gas pressure: • The greater the rate of collisions, the greater the pressure • The faster each molecule moves, the more forceful the collision against the container, the greater the pressure

  12. 3 Ways to Increase Pressure of Gas • Reduce the volume of the container (i.e. compress the gas) • Increases the rate of collisions between gas particles and container • Pump more gas into the container • Increases the rate of collisions between gas particles and container • Heat the gas • Increase speed of gas molecules, collisions are more forceful

  13. Summary of Kinetic Model Distance between Particles Solid Liquid Gas Attractive Force between Particles

  14. Gas Laws • When dealing with gases there are three main properties: • Pressure of Gas (P) • Volume of Gas (V) • Temperature of Gas (T) • There are three gas laws, each one keeping one of the three properties constant • Note: the gas laws only apply if the mass of gas is constant (i.e. no new gas is added or taken away)

  15. Fixed Pressure • If a gas has fixed pressure, • Volume is directly proportional to Temperature • V α T • e.g. when I heat a balloon of air, it will expand

  16. Fixed Volume • If a gas has fixed volume, • Pressure is directly proportional to Temperature • P α T • e.g. when a fixed container of air is heated up, the pressure inside the container increases

  17. Fixed Temperature • If a gas has fixed temperature, • Pressure is inversely proportional to Volume • p α 1/v • e.g. when I compress a volume of air (decrease in volume) the pressure increases

  18. Summary of Gas Laws • When P is fixed, V α T • When V is fixed, P α T • When T is fixed, P α 1/V

  19. Summary • Properties of Solids, Liquids, Gases • Brownian motion as evidence of Kinetic Model • Kinetic Model of Solids • Kinetic Model of Liquids • Kinetic Model of Gases (including pressure) • 3 Gas Laws

  20. 10 min Pop Quiz!!

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