2. The Property of Gases – Kinetic Molecular Theory And Pressure

3. Kinetic Molecular Theory of Gases The word kinetic refers to motion. Kinetic energy is the energy an object has because of its motion. Kinetic Molecular Theory makes assumptions about: ▫ Size ▫ Motion ▫ Energy of gas particles

4. Kinetic Molecular Theory Part 1 1.According to the KMT all matter consists of tiny particles that are in constant, random motion Move in a straight line until they collide with other particles or with the walls of the container.

5. Kinetic Molecular Theory Part 2 2. Gas particles are much smaller than the distances between them. Most of a gas consists of empty space.  Gas consists of small particles that are separated from one another by empty space  Most of the volume of a gas consists of empty space  Because they are so far apart, there are no attractive or repulsive forces between the gas molecules  The motion of one particle is independent of the motion of other particles

6. Kinetic Molecular Theory Part 3 3.No kinetic energy is lost when gas particles collide with each other or with the walls of the container (elastic collision)  Undergoes elastic collision – no kinetic energy is lost when particles collide.  The total amount of kinetic energy remains constant.

7. Kinetic Molecular Theory Part 4 4.All gases have the same average kinetic energy at a given temperature  Temperature is a measure of average kinetic energy of particle in a sample of matter.  Kinetic energy and temperature are directly related  The higher the temperature, the greater the kinetic energy  The Kelvin temperature of a substance is directly proportional to the average kinetic energy of the particles of the substance. 273 + _____ o C = _______Kelvin  There is no temperature lower than 0 Kelvin (Absolute Zero).  Kinetic Energy = ½ mv 2 ; where m = mass and v = velocity

8. Absolute Zero The greater the atomic and molecular motion, the greater the temperature is of a substance. If all atomic and molecular motion would stop, the temperature would be at absolute zero (0 Kelvin or -273 o C)

9. Diffusion and Effusion Diffusion – describes the movement of one material through another ▫ Particles diffuse from an area of high concentration to low concentration Effusion – gas escapes through a tiny opening. The heavier the molecule, the slower it will effuse or diffuse

10. Diffusion and Effusion Diffusion Effusion

11. Pressure Pressure is the force per unit area Gas pressure is the force exerted by a gas per unit surface area of an object.  Gas pressure is the result of billions of collisions of billions of gas molecules with an object Atmospheric pressure (air pressure) results from the collisions of air molecules with objects.  The air pressure at higher altitudes is slightly lower than at sea level because the density of the Earth’s atmosphere decreases as elevation increases. Vacuum - Empty space with no particles and no pressure

12. Measuring Pressure Barometer – an instrument used to measure atmospheric pressure

13. Measuring Pressure Manometer – an instrument used to measure gas pressure in a closed container

14. Units of Pressure and STP Average atmospheric pressure is 1 atm 1atm = 760 torr = 760 mmHg = 101.3 kPa STP (Standard Temperature and Pressure) ▫ 1 atm and 0 o C or 1 atm and 273 K S T P erfecterfect enen 1 0

15. Dalton’s Partial Pressure Dalton’s law of partial pressures states that the total pressure of a mixture of gases is equal to the sum of the pressures of all the gases in the mixture. P total = P 1 + P 2 +P 3 +... P n

16. Conversion Factors for Pressure 1 atm = 760 torr = 760 mmHg = 101.3 kPa

17. Example 1 Convert 2.5 atm into torr, mmHg, kPa 2.5 atm 760 torr 1 atm = 1900 torr 2.5 atm 760 mmHg 1 atm = 1900 mmHg 2.5 atm 101.3 kPa 1 atm = 250 kPa

18. Example 2 Convert 215 kPa into torr, mmHg, atm 215 atm 760 torr 101.3 kPa = 1610 torr 215 atm 760 mmHg 101.3 kPa = 1610 mmHg 215 atm 1 atm 101.3 kPa = 2.12 atm

19. Dalton’s Law of Partial Pressures P total = P 1 + P 2 + P 3 … + P n

20. Example 1 P total = P O 2 + P CO 2 + P N 2 0.97 atm = P O 2 + 0.70 atm + 0.12 atm P O 2 = 0.15 atm

21. Example 2 P total = P O 2 + P CO 2 + P CO P total = 0.563 atm + 2.32 atm + 0.599 atm P total = 3.48 atm 235 kPa 1 atm 101.3 kPa = 2.32 atm 455 torr 1 atm 760 torr = 0.599 atm **You first have to put everything in the same units!

22. COCl 2

23. C 2 H 2 AsCl 3

24. Cl 3 CNO 2

25. C 4 H 8 Cl 2 S