3. The Property of Gases – Kinetic Molecular Theory explains why gases behave as they do http://preparatorychemistry.com/KMT_flash.htm https://www.wisc-online.com/learn/natural- science/chemistry/gch4904/the-kinetic-theory-of-gases

4. 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

5. Kinetic Molecular Theory Kinetic Molecular Theory 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.

6. Kinetic Molecular Theory Kinetic Molecular Theory 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

7. Kinetic Molecular Theory Kinetic Molecular Theory 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.

8. Kinetic Molecular Theory Kinetic Molecular Theory 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 http://www.dlt.ncssm.edu/core/Chapter11- Thermochemistry/Chapter11-Animations/KineticEnergy-Gas.html

9. Absolute Zero 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)

10. 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

11. 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

12. Characteristics of gases Gases can be compressed. ◦no volume = lots of empty space Gases undergo diffusion & effusion. ◦random motion

13. Diffusion and Effusion Diffusion and Effusion Diffusion Effusion

14. Diffusion and Effusion 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

15. Pressure 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

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

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

18. 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

19. THE GAS LAWS

20. Pressure - Temperature - Volume Relationship Boyle’s Law: Pressure is inversely proportional to volume Charles’ law: Volume and temperature are

21. Properties of gases Gas properties can be modeled using the following units and measurements: Volume of the gas (Liters, L) Temperature (Kelvin, K) Pressure (atm,torr, psi, pa, Kpa)

22. 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

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

24. 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

25. 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 Example 2

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

28. 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

29. 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!