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BIG CHILL PROJECT – 5%

BIG CHILL PROJECT – 5%. Goal: Build a container that keeps an ice cube from melting for the longest period of time. Must be 15.0cm x 15.0cm x 15.0cm or smaller. Must operate at room temperature with no electricity. Must be an original creation. BIG CHILL PROJECT.

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BIG CHILL PROJECT – 5%

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  1. BIG CHILL PROJECT – 5% Goal: Build a container that keeps an ice cube from melting for the longest period of time. • Must be 15.0cm x 15.0cm x 15.0cm or smaller. • Must operate at room temperature with no electricity. • Must be an original creation.

  2. BIG CHILL PROJECT • Must have a opening and chamber big enough to accommodate an ice cube.

  3. BIG CHILL PROJECT Grade is two parts: 1. Construction - 50 pts 2. Efficiency - 50 pts Bonus points for being a top three finisher in your class, the best design in your class, ice cube lasting longer than 8 hours, and a parent signature on the blue form. DUE THURSDAY MARCH 14

  4. OBJECTIVES • Describe the effect on a gas by a change in the amount of gas (moles), the pressure of gas, the volume of gas, and the temperature of gas. • Be able to perform calculations using Boyle’s Law, Charles’ Law, and Gay-Lussac’s Law. • Be able to use Dalton’s Law of Partial Pressures in a calculation • Distinguish between real and ideal gases. Be able to tell how real gases differ from ideal gases. • State the ideal gas law and know what each symbol stands for • Perform calculations using the ideal gas law and the combined gas law. • State and use Graham’s Law of Diffusion. • Be able to calculate gas stoichiometry problems (volume – volume, mass – volume, volume – mass). • Be able to calculate density and molecular mass using the ideal gas law formula.

  5. GAS LAWS Chapters 12-13

  6. PRESSURE (Chapter 12) • Pressure is the force per unit area. • Gases exert pressure when they hit the walls of their container. • To measure air pressure, you might use a barometer or a manometer. A barometer measures atmospheric pressure. A manometer measures the internal pressure of an enclosed gas.

  7. PRESSURE • There is pressure exerted by the atmosphere. At sea level this pressure is equal to one atmosphere.

  8. PRESSURE DEMO Fig Newtons

  9. PRESSURE • Pressure is measured in a variety of units. *We will use all of these but psi.

  10. VIDEODISC • Chapter 2 – Racing Hot Air Balloons • Why is it easier for pilots to control the vertical direction of a balloon’s flight than the horizontal direction? • Why did Julie say that a thermal is not a good word for balloonists?

  11. GASES (Chapter 12) Physical Properties of Gases: • Gases have mass. • Gas particles do not attract or repel each other. • It is easy to compress gases. • Gas molecules are in constant motion • Gases fill their containers completely • Different gases can move through each other quite rapidly. • Gases exert pressure. • The pressure of a gas depends on its temperature and volume.

  12. GASES • Remember that gases consist of very small particles, the particles have large distances between them, they are in constant, rapid, random motion and have elastic collisions. • Actual gases (in real life) do not obey all the suppositions stated in the kinetic-molecular theory. • In order to accurately measure a gas sample, you must know the quantity of particles (moles), pressure, temperature, and volume of a gas.

  13. THE GAS LAWS (Chapter 13) • Boyle’s Law: V and P; inversely proportional. • Charles’ Law: T and V; directly proportional. • Gay-Lussac’s Law: P and T; directly proportional. • Avogadro’ Principle: moles and P or V; directly proportional.

  14. THE GAS LAWS DEMOS – Boyle’s Law • Chapter 7 – Breathing and Boyle’s Law 1. Why does the balloon expand? 2. What does this demo have to do with breathing? 3. Have you ever heard the phrase “nature abhors a vacuum?” What do you think it means? • Cartesian Diver • World record dive • Balloon and bottle • Artificial lung

  15. BOYLE’S LAW

  16. BOYLE’S LAW THE LAW: For a given mass of gas, at a constant temperature, the volume varies inversely with the pressure: P1V1= P2V2 PRACTICE: The pressure in a 9.0 L balloon is 2.1 atm. If the volume is reduced to 5.0 L, what will the resulting pressure be? (Temperature does not change.) V1= 9.0 L V2 = 5.0 L P1= 2.1 atm P2 = ? atm P1V1= P2V2P2= P1V1 = V2

  17. REMINDER EVERY TIME you do a gas laws problem: • Write what you know and what you are trying to find • Write the formula • Plug in the numbers with units and solve with the correct number of sig figs.

  18. GAS LAWS DEMO • Balloon and temperature change

  19. CHARLES’ LAW

  20. CHARLES LAW THE LAW: The volume of a fixed mass of a gas is directly proportional to its KELVIN temperature if the pressure is constant. If pressure is kept constant, then volume must change to keep temperature the same. V1 = V2 T1T2 You must use the Kelvin temperature scale! K = °C + 273 PRACTICE: The temperature of a sample of gas is 300.0 K. The gas’ volume is 25.0 L. What will be the new volume of the gas if the temperature is dropped to 125.0 K? V1= 25.0 L V2= ? L V2 = T2V1 = T1= 300.0 K T2= 125.0 KT1

  21. GAS LAWS • Videodisc – Chapter 5 - Imploding Can 1. Why did the can implode? 2. How does the demonstration you just saw relate to a barometer? 3. How is a vacuum seal created on a jar of homemade preserves? • Egg in a bottle • Bulb with pressure gauge

  22. GAY-LUSSAC’S LAW

  23. GAY-LUSSAC’S LAW THE LAW: An increase in temperature increases the frequency of collisions between gas particles. In a given volume, raising the KELVIN temperature also raises the pressure. P1 = P2 T1 T2 You must use Kelvin temperature scale! PRACTICE: The temperature of a sample of gas is 300.0 K. The gas’ pressure is 1.4 atm. What will be the new pressure of the gas be if the temperature is dropped to 125.0 K? P1= 1.4 atmP2= ? atmP2= T2P1 = T1= 300.0 K T2= 125.0 K T1

  24. REMINDER EVERY TIME you do a gas laws problem: • Write what you know and what you are trying to find • Write the formula • Plug in the numbers with units and solve with the correct number of sig figs.

  25. DO NOW • Pick up handout – due tomorrow • Copy problem set info - due Feb. 25 Ch. 12 #1, 2 Ch. 13 #1, 2, 5, 6, 8, 9, 11,16, 21, 26, 27, 36, 38, 39, 42 • Paper towel drive ends Friday, 3:30. • Balloons and Cans lab due Feb. 19.

  26. HINT PTV

  27. PUTTING IT ALL TOGETHER Simulation on gas laws: Structure and Properties of Matter

  28. AVOGADRO’S PRINCIPLE Volume: 22.4L 22.4L 22.4L Mass: 39.95g 32.00g 28.02g Quantity: 1 mol 1 mol 1 mol Pressure: 1 atm 1 atm 1 atm Temperature: 273K 273K 273K

  29. AVOGADRO’S PRINCIPLE DEMO Beach Ball

  30. AVOGADROS’S PRINCIPLE • Particles of different gases vary greatly in sizes. But size is not a factor • The Law: equal volumes of gases at the same temperature and same pressure contain equal number of particles. • In gas law problems moles is designated by an “n”. • One mole of a gas has a volume of 22.4 L (dm3) at standard temperature and pressure (STP). It also has 6.02 x 1023 particles of that gas.

  31. DALTON’S LAW OF PARTIAL PRESSURES

  32. DALTON’S LAW OF PARTIAL PRESSURES THE LAW: The sum of the partial pressures of all components of a gas mixture is equal to the total pressure of the gas mixture. Ptotal= P1 + P2 + P3 + P4 +..... PRACTICE (Easy Type): What is the atmospheric pressure if the partial pressures of nitrogen, oxygen, and argon are 604.5 mm Hg, 162.8 mm Hg, and 0.500 mm Hg, respectively? Ptotal = P1 + P2 + P3 Ptotal =

  33. DALTON’S LAW OF PARTIAL PRESSURES (Chapter 12)

  34. DALTON’S LAW OF PARTIAL PRESSURES PRACTICE (Hard Type): A quantity of oxygen gas is collected over water at 8C in a 0.353 L vessel. The pressure is 84.5 kPa. What volume would the DRY oxygen gas occupy at standard atmospheric pressure (101.3 kPa) and 8C. (The dry gas pressure of water at 8C is 1.1 kPa) T1 = 8ºC T2 = 8ºC V1 = 0.353L V2 = ? P1 = 84.5 kPa – 1.1 kPa = 83.4 kPa P2 = 101.3 kPa You must correct the pressure so that you can have the DRY gas without the water pressure added in.  P1V1 = P2V2 V2 = P1V1 = P2

  35. GAS LAWS Videodisc – Chapter 9 Scuba Diving • Think about your lungs as a flexible 6-liter container full of a gas at STP. How would lung volume change at a depth of 30 meters? • Why not increase the oxygen to 100% and go really deep? • What are the bends? How do divers avoid them?

  36. COMBINING THE LAWS From the Boyle’s, Charles’, and Gay-Lussac’s laws, we can derive the CombinedGas Law: P1V1 = P2V2 T1 T2 Mnemonic:Potato and Vegetable on top of the Table

  37. COMBINED GAS LAW PRACTICE: The volume of a gas measured at 75.6 kPa pressure and 60.0°C is to be corrected to correspond to the volume it would occupy at STP. The measured volume of the gas is 10.0 cm3. P1 = 75.6 kPa P2 = 101.3 kPa P1V1 = P2V2 V1 = 0.0100 L V2 = ? T1 T2 T1 = 333.0K T2 = 273 K V2 = P1V1T2 = ___________________________ T1P2

  38. STANDARDS T = 0°C = 273 K V = 22.4 L (at STP) P = 1.00 atm= 101.3 kPa = 760.0 mm Hg = 760.0 torr Remember only kPa has limited sigfigs.

  39. COMBINED GAS LAW PRACTICE: Correct the volume for a gas at 7.51 m3 at 5.0°C and 59.9 kPa to STP.

  40. IDEAL GAS LAW Ideal Gas Equation: PV = nRT “R” is the universal gas constant.

  41. UNIVERSAL GAS CONSTANTS R = 0.0821 L• atm mol• K R = 62.4 L•mm Hg mol• K R = 62.4 L • torr mol• K R = 8.31 L • kPa mol • K Why are there four constants?

  42. IDEAL GAS LAW Remember: • Always change the temperature to KELVINS and convert volume to LITERS • Check the units of pressure to make sure they are consistent with the “R” constant given or convert the pressure to the gas constant (“R”) you want to use.

  43. IDEAL GAS LAW PRACTICE: How many moles of a gas at 100.0°C does it take to fill a 1.00 L flask to a pressure of 1.50 atm? V = 1.00 L T = 100.0°C = 373.0 K P = 1.50 atm R = 0.0821 atm•L n = ? mol•K PV = nRT n = PV = ____________________________ = RT

  44. IDEAL GAS LAW PRACTICE: What is the volume occupied by 9.45g of C2H2 at STP? Hint - convert grams to moles..... 9.45g C2H2 1 mol C2H2 = 0.363 mol 26.04g C2H2 P = 1.00 atm R = 0.0821 atm•L V = ? mol•K n = 0.363 mol T = 273.0K

  45. PRACTICE P = 1.00 atm T = 273K V = ? R = 0.0821 L· atm N = 0.363mol mol· K V = nRT= (0.363mol)(273K)(0.0821 L· atm)= P (1.00 atm) (mol· K) = 8.14L

  46. GRAHAM’S LAW OF EFFUSIONor DIFFUSION (Chapter 12) The rate of diffusion/effusion is inversely proportional to the square root of its molar mass under identical conditions of temperature and pressure. If two bodies of different masses have the same kinetic energy, the lighter body moves faster.

  47. DEMO • Anise and Cinnamon • What can we assume about the temperatures of the two oils? • How is temperature related to KE? • How doe the KE of the two oils compare? • What is the formula for KE?

  48. CALCULATIONS • KE = ½mv2 • ½ mava2 = ½ mcvc2 • ½ mava2= ½ vc2 mc • ½ ma= ½ vc2 mc va2 • ma= vc2 mc va2

  49. GRAHAM’S LAW OF EFFUSIONor DIFFUSION (Chapter 12) Rate (velocity) a = Formula mass b Rate (velocity) b Formula mass a Compare ammonia and hydrochloric acid: velocity NH3 = 36.45g/mol velocity HCl 17.04g/mol = NH3 is 1.46 times faster than HCl

  50. REAL vs. IDEAL GASES • The ideal gas equation, PV = nRT, is simple to use and accurately predicts gas behavior in many everyday situations. • Under very high pressure, real gases have trouble compressing completely. The ideal gas law fails. Ideal gases have no volume, but real gases do.

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