1 / 20

Kinetic Theory and Gases

Kinetic Theory and Gases. Objectives. Use kinetic theory to understand the concept of temperature. Be able to use and convert between the Celsius and Kelvin temperature scales. Kinetic Theory. kinetic theory : all matter is made of particles (atoms,

pmcdonald
Download Presentation

Kinetic Theory and Gases

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Kinetic Theory and Gases

  2. Objectives • Use kinetic theory to understand the concept of temperature. • Be able to use and convert between the Celsius and Kelvin temperature scales.

  3. Kinetic Theory kinetic theory: all matter is made of particles (atoms, ions, molecules) that are in constant, random motion kinetic energy (or KE): the energy of motion; depends on both the mass and speed of the moving particles number of particles temperature (T): a measure of the average KE of all the particles in a substance NOT T-E-M-P ! Kinetic Energy

  4. Kelvin Scale absolute zero: the coldest possible T; there is no molecular motion; KE = 0 (= -273oC or 0 Kelvin) K = oC + 273 oC = K - 273 Kelvin temperature is directly proportional to the KE! KE 0 oC ≠ 0 KE 0 K = 0 KE 200K has 2X more KE than 100K T

  5. Objectives • Understand the concept of atmospheric pressure. • Be able to explain how a barometer works. • Be able to convert between pressure measurements.

  6. Gases and Pressure Gases exert pressure by collisions. pressure: force applied over an area metric pressure unit: 1 pascal (Pa) = 1 N/m2 Atmospheric pressure is 14.70 lbs/in2 at sea level. spheres DEMO! barometer: instrument that measures atmospheric pressure

  7. Pressure Conversions standard pressure (P) = 14.70 psi = 760.0 mm Hg = 29.92 in Hg = 101.3 kPa = 1.000 atm standard temperature (T) = 0oC or 273 K STP: standard T and P What is the current pressure in kPa and atm?

  8. CAN SMASH • Have about 1 inch of water in the bowl plus at least one large ice cube. • Remove tab from rinsed can. Place about 1/8” of water in the can. • Hold can with tongs—palm up! • Heat the water over the burner, shaking can regularly. Allow water to boil—steam forms. • Shake out any excess water. Heat briefly again. • Plunge top of can into the ice water!

  9. Objectives • Be able to use the pressure equation to explain pressure, temperature, and volume changes in gases. • Understand how to solve word problems using the “GUESS” method. • Be able to use the various gas laws to solve problems.

  10. The G-U-E-S-S Method • G = list the “given” values • U = list the “unknown” • E = find the correct equation • S = solve for the unknown (use algebra!) • S = substitute the values and solve

  11. Boyle’s Law temperature (in K scale) • force (F) relates to temperature (T) • area (A) relates to volume (V) volume Boyle’s Law (T is constant ) P and V are inversely proportional At constant temperature, 7.5 L of air at 89.6 kPa is compressed to 2.8 L. What is the new pressure? Demo: balloon in vacuum

  12. Charles’s Law and the P-T Law Charles’s Law (P is constant ) V and T are directly proportional *must use Kelvin P-T Law (V is constant ) P and T are directly proportional *must use Kelvin Demos: hot squirt bottle, space modulator gun

  13. Gas Law Problems (use GUESS method) (1) A 3.0 L balloon inside a -22oC freezer is removed and placed into a room at 19oC. What is the new volume if the pressure remains the same? What law was used? • A solid container of gas at STP is heated and the • pressure increases to 158 kPa. What is the new • temperature of the gas? What law was used?

  14. Objectives • Understand how the various gas law equations are derived. • Be able to use the ideal gas law, gas molar mass equation, and gas density equation to solve problems.

  15. More Gas Laws Combined Gas Law Gas Molar Mass Ideal Gas Law n = # moles Gas Density R = 8.31 kPaL/molK

  16. More Gas Law Problems • What is the molar mass of a gas that has a mass of 0.35 g and occupies 165mL at 95oC and 87.0 kPa? • How many moles of air are in a 3.2 L balloon under the current temperature and pressure conditions in this room? • What is the density of N2 gas at 95 kPa and 25oC?

  17. Objectives • Understand Avogadro’s law by considering the ideal gas law. • Be able to use the law of combining gas volumes to solve simple gas stoichiometry problems. • Be able to use the ideal gas law to solve more complex gas stoichiometry problems.

  18. Avogadro’s Law Avogadro’s Law: equal volumes of gases at the same T and P contain equal numbers of molecules (n) O2 He CO2 Why? Look at the Ideal Gas Law!

  19. Law of Combining Gas Volumes Coefficients can represent gas volumes if the reactants and products are at equal T and P. N2(g) + 3H2(g) → 2NH3(g) How many liters of H2 are needed to completely react with 2.5 L N2? Assume same T and P. 1 vol. 3 vol. 2 vol. 1 L 3 L 2 L

  20. Gas Stoichiometry g A → mol A → mol B → g B g A → mol A → mol B → L B (use V = nRT/P) • (1) How many liters of CO2 at 23oC and 89.5 kPa are • formed when a 468 g container of C3H8 is burned? • C3H8 + 5 O2 → 3 CO2 + 4 H2O • How many liters of H2 gas are formed when 0.25 g • Na reacts with HCl at STP? • 2Na + 2HCl → H2 + 2NaCl

More Related