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Kinetic molecular theory

Kinetic molecular theory. What is the difference between kinetic and potential energy?. Basic gas laws IDEAL GAS LAWS What are the characteristics of an ideal student?. Observe the movement of gas particles. Comment on their movement. Write your observation.

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Kinetic molecular theory

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  1. Kinetic molecular theory What is the difference between kinetic and potential energy?

  2. Basic gas laws IDEAL GAS LAWS What are the characteristics of an ideal student?

  3. Observe the movement of gas particles. Comment on their movement. Write your observation.

  4. Gas is made of very tiny atoms or molecules and they move very fast. • Particles move in straight lines.

  5. 3. The gas particles are very small (size is negligible) compared to the size of the surrounding

  6. 4. Gas particles do not have any attraction between them.

  7. What will happen to the energy if a volley ball is dropped? • Will it lose energy? Can it keep going for ever?

  8. 5. When gas particles collide energy or speed is not lost.

  9. This is what happens not in REAL situation but in an IDEAL one • That is why we call these rules ‘ideal’ gas laws. • In real situations, it will vary.

  10. Real Gases • Particles in a REAL gas… • have their own volume • attract each other • When do students behave as ‘ideal’ students? (under what circumstances? )

  11. Gas behavior is most ideal… • at low pressures • at high temperatures • in nonpolar atoms/molecules

  12. Relation between temperature and speed of particles.

  13. Speed of particle movement and temperature are related.

  14. When particles move fast, temperature increases.

  15. When particles move slowly, temperature decreases.

  16. What is pressure? A quick write.

  17. Collision of particles on the walls of the container causes pressure.

  18. Speed of particles temperature

  19. What is the impact on gas molecules if the temperature is increased? Will the pressure increase or decrease? This is a closed system.

  20. When temperature increases the speed of the particles and the number of collisions increase. There will be more pressure in a closed system.

  21. Higher temperature decreases pressure in an open environment because gas expands and particles are separated.

  22. Characteristics of Gases • Gases expand to fill any container. • random motion, no attraction • Gases have very low densities. • no volume = lots of empty space

  23. Characteristics of Gases • Gases can be compressed. • no volume = lots of empty space • Gases undergo diffusion

  24. 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

  25. 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?

  26. Avagadro's Hypothesis Equal volumes of gases at the same T and P have the same number of molecules. V = n(RT/P) = kn This means, for example, that number of moles goes up as volume goes up. 1 mole = 6.022 x 1023

  27. One mole of any gas at STP occupies 22. 4 liters

  28. N2 CH4 Ar H2 Avogadro’s Hypothesis At the same temperature and pressure, equal volumes of different gases contain the same number of molecules. Each balloon holds 1.0 L of gas at 20oC and 1 atm pressure. Each contains 0.045 mol or 2.69 x 1022 molecules of gas.

  29. If you double the number of molecules 1 atm

  30. If you double the number of molecules… You double the pressure. 2 atm

  31. As you remove molecules from a container the how will it affect pressure? 4 atm

  32. As you remove molecules from a container the pressure decreases. 4 atm

  33. As you remove molecules from a container the pressure decreases • Until the pressure inside equals the pressure outside • Molecules naturally move from high to low pressure 1 atm

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

  35. STP STP Standard Temperature & Pressure 0°C 1 atm 273 K - OR - 101.325 kPa 760 mm Hg

  36. Vapor pressure

  37. H2O(g) molecules (water vapor) H2O(l) molecules Evaporation

  38. Boiling vs. Evaporation Boiling point: atmospheric pressure = vapor pressure AIR PRESSURE 15psi VAPOR PRESSURE 15 psi Evaporation: molecules go from liquid to gas phase gas liquid

  39. Boiling Point on Mt. Everest Water exerts a vapor pressure of 101.3 kPa at a temperature of 100 oC. This is defined as its normal boiling point: ‘vapor pressure = atmospheric pressure’

  40. Behavior of a liquid in a closed container

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