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Day 1:

Day 1:. Properties of Gases Lab. Gases. Chapter 12. Day 2: Properties of Gases. Gases… Are fluids (able to flow) Have low density (mostly empty space) Are highly compressible (can be relatively easy to squeeze into smaller spaces) Completely fill a container (few attractive forces)

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Day 1:

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  1. Day 1: • Properties of Gases Lab

  2. Gases Chapter 12

  3. Day 2: Properties of Gases • Gases… • Are fluids(able to flow) • Have low density(mostly empty space) • Are highly compressible(can be relatively easy to squeeze into smaller spaces) • Completely fill a container(few attractive forces) • Have pressure(caused by collisions of molecules)

  4. Pressure • The amount of force exerted per unit area of surface 101.3kPa = 760 mm Hg = 760 torr = 1atm Units of Pressure: • kilopascals (kPa) • millimeters of mercury (mm Hg) • Torr (torr) • atmospheres (atm)

  5. Converting Pressure 1. 65 kPa = ______ atm 2. 880 mm Hg = ______ kPa

  6. Pressure Pressure vs Surface Area: • Less surface area = more pressure • Larger surface area = less pressure

  7. Temperature • Temperature is the measurement of the average speed of moving particles. • ALWAYS CONVERT TEMP TO KELVIN!!! K = C + 273

  8. Standard Temperature and Pressure (STP) • Conditions under which scientists typically study gases • For a gas at STP: • temperature = 273 K (0oC) • pressure =1.00 atm

  9. The Physical States of Matter • Matter can be classified as solid, liquid, or gas based on what properties it exhibits. • Fixed = Keeps shape when placed in a container. • Indefinite = Takes the shape of the container.

  10. Kinetic Molecular Theory (KMT) of Matter • Model used to predict gas behavior All matter is made of constantly moving particles.

  11. KMT • Gas particles are small, hard spheres with insignificant volume (therefore most of the volume of a gas is empty space) • Gas particles are very far apart relative to their size • There are no attractive or repulsive forces between particles or particles and the walls of the container • Gas particles are in constant, random motion • Gas particles travel in straight-lime paths until they collide with each other and the walls of their container • Gases have perfectly elastic collisions (energy is completely transferred during collisions)

  12. HW - questions on p.2-3

  13. Day 3: Gas Laws Boyles LawCharles Law Gay-Lussac’s Law Avogadro’s Law Combined Gas Law

  14. Measurable Properties of Gases Pressure (P) Temperature (T) Volume (V) Number of moles of gas (n)

  15. Reminders: • Gases exert pressure through the collisions of its particles with the walls of its container • While studying the gas laws we will be using the Kelvin scalefor temperature • Volume is the space the object (gas) occupies

  16. Boyles LawBoyle studied the relationship btw Pressure & Volume • Looking back at your lab, when you decreased the volume in the syringe what happened to the pressure???? What is the relationship between Pressure and Volume? • As volume decreases, pressure increases, vice versa. • Inversely proportional

  17. 2 liters 1 liter Filled with gas Empty

  18. Boyles Law • What happens when a sample of gas is changed how can I predict what is going to happen? P1 x V1 = P2 x V2 ** Make sure pressure and volume units are the same!!!!!

  19. Pressure vs. Volume Example • A sample of oxygen gas occupies a volume of 250 mL at 0.88 atm. What volume will it occupy at 1.2 atm? Work: 0.88atm(250) = 1.2V Ans: 183 mL

  20. Charles’s LawCharles studied the relationship btw VolumeandTemp of a gas • Thinking back to our lab when you put a balloon in ice water, what happened? What about when it was in the warm water? What is the relationship between temperature and volume? • As temperature increases, volume increases, vice versa • directly proportional

  21. Charles Law • What happens when I change the temperature or volume of the gas, how do I predict the results? = ** Make sure temperature and volume units are the same!!!!!

  22. Temperature vs. VolumeExample • When measured at a temperature of 60oC, a volume of gas is 600mL, what is the volume at 10oC? Work: Ans: 509.9 mL

  23. Gay-Lussac’s Law Gay-Lussac studied the relationship btw PressureandTemp • Think about cooking pasta on the stove, you turn off the burner, but keep the lid on the pot so the food stays warm, when you go to take the lid off, it’s stuck! • What can you do to get the lid off? • Why does this happen?? • What is the relationship between pressure and temperature? • As temperature increases, pressure increases, vice versa • Directly proportional

  24. Gay-Lussac’s Law • How can I predict what would happen if I changed the pressure or temperature? ** Make sure units are the same!!!!!

  25. Pressure vs. TemperatureExample • A sample of oxygen gas is at 45oC at 0.88 atm. What pressure will it have at 100oC? Work: Ans: 1.03 atm

  26. Avogadro’s LawAvogadro studied the relationship between the #of moles and volumeof a gas • If we fill a balloon with 1 liter of helium, how do we get the balloon to be bigger? • Increases in the amount of air = an increase in the number of moles What is the relationship between moles and volume? • As the number of moles increase, the volume increases, vice versa • directly proportional

  27. Avogadro’s Law • How can I predict what would happen to the volume if I changed the number of moles? ** Make sure units are the same!!!!!

  28. Number of Moles vs. Volume Example • If 2.6 moles of helium are used to fill a balloon up to 3 mL of air, how many are needed to fill the balloon to 5 mL? Work: Ans: 4.33 mol

  29. Recap! Work on the bottom of p.5 Charles' Law, As the temperature increases the volume increases proportionally Boyle's Law, As the pressure increases the volume decreases proportionally Gay Lussac's Law, At constant volume as the temperature increases the pressure increases proportionately

  30. Day 4: Finish Gas Laws & Combined Gas Law Finish Notes Demos Calculations Practice

  31. Combined Gas Law All of the above gas laws can be put together into what is called the Combined Gas Law The combined gas law is used when a gas is undergoing a change from one set of conditions to another Only use the portions of this law that apply to the particular problem

  32. Example 1: • A sample of gas occupies 1.55 L at 27.0oC and 1.00 atm of pressure. What will the volume be if the pressure is increased to 50.0 atm, but the temperature is kept constant? • Answer: • 0.031 L

  33. Example 2: • A sample of gas occupies 1.55 L at 27.0oC and 1.00 atmof pressure. What will the volume be at -100oC and the same pressure? • Answer: • 0.894 L

  34. Work p.8-10 select numbers

  35. Day 5 • Practice Gas laws on p.10-12 ALL Have a Nice Spring Break!!

  36. Day 6 – Welcome Back!!Hope you had a nice spring break! • Review using p.6-7 • Check and go over p.10-12, gas law equations • More combined gas law practice worksheet

  37. Day 7: Ideal vs Real Gases

  38. Ideal Gas • An imaginary gas whose particles are infinitely small and do not interact with each other • Perfectly follow all of the gas laws under all conditions • Small, monatomic gases are the closest thing we have to ideal gases • Helium

  39. Ideal vs. Real Gases Ideal gases will not condense to a liquid at low temperatures, while real gases will condense Ideal gases will not have forces of attraction or repulsion between particles, while real gases will have intermolecular forces Ideal gases have particles with no volume, while the particles of real gases will always have volume

  40. Ideal vs. Real Gases Real gases do not behave ideally at high pressures

  41. Ideal vs. Real Gases Real gases do not behave ideally at low temperatures

  42. Ideal Gas Law The law that states the mathematical relationship for a gas under a certain set of conditions This only works when a gas experiences one set of conditions Constants: Use the combined gas law when conditions change

  43. Example 1: • How many moles of argon are there in 20.0 L at 25oC and 96.8kPa? • Answer: • 0.78 mol

  44. Example 2: • A sample of CO2 has a mass of 35.0g and occupies 2.5L at 400K. What pressure does the gas exert? • Answer: • 1057.5 kPa

  45. Ideal Gas Law Practice p. 14 Due tomorrow!

  46. Day 8 • Partial Pressure

  47. Diffusion Molecules move from areas of high concentration to lower concentration until the concentration is uniform throughout.

  48. Effusion The passage of a gas under pressure through a tiny opening

  49. Graham’s Law of Diffusion The law that states that the rate of effusion of a gas is inversely proportional to the square root of the gas’s molar mass Heavier gases diffuse (and effuse) more slowly than lighter gases

  50. Partial Pressure

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