1. What changes about the atoms in a substance as it gets warmer? They move faster! boltzmann distribution applet

2. What are 3 Temperature Scales that we use? Fahrenheit – Not used in Science Celsius ( o C) – based on water Kelvin (K) – based on absolute Zero

3. Can it get colder than… 0 o F 0 o C 0 K ABSOLUTE ZERO- atoms slow down as a sample gets colder. What is the slowest that atoms can move?

4. K = o C + 273

5. How can you tell that there is pressure in soda bottle Before you open it? If you push on it, it pushes back right? The pressure on the inside of the bottle, has two components: Area Force

6. The area is easy– the inside of the bottle BUT WHAT IS CAUSING THE FORCE????? How can molecules of air exert a force on the inside of the container? Do they push?

7. What are the air molecules in the room doing now? Moving, but how? In a straight line until…. If the pressure is cause by collisions (like cars) why don’t I see things getting bounced around?

8. But molecules are so small and light. How can they produce enough force that I can feel it push back against a soda bottle.

9. Gas particles and pressure animation Lets consider a gas inside a soda bottle. What could I do to make the pressure inside the soda bottle INCREASE

10. Add more gas because…. 3 ways to increase pressure of a gas inside a container: Increase the temperature because…. Decrease the volume of the container because…

11. Can only liquid be fluids? Both liquids and gases are fluids and exert a pressure on anything surrounded by them Is there any pressure on us now?

12. Yes, we are in a “Pool of air” at the very bottom Pressure = Force Area What is the force on 1 in 2 due to air. Guess by the weight of so many paperclips

13. Demo: Magdeburg sphere

14. Why were the spheres so hard to open after using the vacuum pump? Why were the spheres so EZ to open after the valve was opened? Other than opening the valve to let air in, what else would make the spheres easy to open? If we could get a perfect vacuum inside the sphere, would it be possible to open them?

15. The equivalent of a stack of paperclips would be 6700 on every square inch of your body Air pressure is pushing down 14.7 pounds in 2 The spheres have an area of about 11 in 2 on each side = 160 # pulling on each side

16. Gases fill a container right? What is the container on the earth? Why doesn’t the gas leave to fill the universe? The top of a sea of water is very easy to see right? What about the top of the atmosphere?

17. The radius of the earth is 4,000 miles 99% of the atoms in the atmosphere are within 19 miles The thickness of the line How far out from the earth would 99% of all the atoms in the atomosphere be?

18. How much would the air in this room weigh? The volume of the room is about 10*30*20 = 6000 m 3 The density of air (at ground level) is 1.25 kg/m 3 The mass of the air in this room is about 7500 kg Or 3,300# ( the weight of a car!!!!!)

19. If I fill a test tube full of water and invert it in a cup of water what happens? Could I do this with a 1 foot test tube of water? Could I do this with a 10 foot test tube? Could I do this with a 100 foot test tube? There is a limit to the height of a water column that air pressure will hold up! WHY?

20. Average air pressure will push up ~32 ft of water. Why did I say average? What happens to the water column when air pressure goes up?

21. A 32 foot barometer is not too practical, how could I make it shorter?

23. No pressure Atmospheric Pressure How can air pressure pushing down hold up a liquid? 760 mm Hg

24. Evangelista Torricelli 1608-1657 Inventor of the barometer

25. Hired by a pump manufacturer to solve a problem No matter what was done, water could not be “sucked” up by a pump more than 32 feet above the water level. 40 ft

26. He had read Galileo’s work on the weight of air, and new the problem at once. In attempt to prove his theory he experimented with mercury filled glass tubes. The height of the mercury column invariable fell to a height of ________ above the Hg surface 760 mm

27. The prominent scientific theory as to what held the column up was that “nature abhors a vacuum” He reasoned that if the resistance to vacuum has holding up the column. Then a taller tube should have a taller column of mercury

29. But……..

30. Another theory was that invisible strings were holding the liquid up

31. But the his theory was generally accepted after he took his barometer climbing

32. The level dropped the higher he climbed!!

33. Pressure can be expressed two ways Force Area or Height of a column of liquid 1 ATM=14.7 101.35 kPa - kilopascal 760 mm Hg 760 Torr 29.92 in Hg psi

34. STP = 0 o C or 273 K Standard Temperature & Pressure 1 ATM=14.7 101.35 kPa - kilopascal 760 mm Hg 760 Torr 29.92 in Hg psi 101,350 Pa

35. How does a drinking straw work? You suck up the liquid right?

36. How strong is a balloon? If there is 14.7 POUNDs crushing down on every square inch of the outside of a fragile balloon, WHY IS IT NOT CRUSHED????

37. What would happen if I increased the pressure on the outside of the balloon by taking it under water?

38. It decreases in volume, WHY? As the volume decreases, the pressure goes up Right? Because the air molecules repel each other?

39. For a gas Pressure Volume What would the volume of a 6 L balloon be if I doubled the pressure on it?

40. P 1 V 1 = P 2 V 2 Boyle’s Law Initial Pressure Initial Volume Final Pressure Final Volume P 1 & P 2 CAN HAVE ANY UNITS but they must match V 1 & V 2 CAN HAVE ANY UNITS but they must match

41. What would happen if I took a balloon and put it in the fridge? Why? What is the same B4 & After?

42. For a gas Temperature Volume (at a constant pressure) What would the volume of a 6 L balloon be if I doubled its temperature?

43. V 1 V 2 Charles’ Law Initial Temperature (K) Initial Volume Final Temperature (K) Final Volume T 1 & T 2 MUST BE IN KELVIN V 1 & V 2 must have the same units T 1 T 2 =

44. Taking a balloon out for a stroll

45. What if an aerosol can was placed in a fire, assuming it does not rupture what changes?

46. For a gas TemperaturePressure Assuming that ….

47. P 1 P 2 Initial Temperature (K) Initial Pressure Final Temperature (K) Final Pressure T 1 & T 2 MUST BE IN KELVIN P 1 & P 2 must have the same units T 1 T 2 =

48. Practice What is the volume of a 10 L balloon if the pressure on it is increased from 2 atm to 6 atm?

49. What would the pressure of a rigid can at 50 Pa if its temperature was raised from 150 K to 300 K? 150 o C to 300 o C?

50. In order to make a 5 gallon balloon at 100 Kelvin shrink to 1 gallon, what would the final temperature be?

51. What would the volume of a 6 L balloon be if I doubled its temperature and pressure?

52. Ideal Gas Laws Assumptions 1.) The particles in a gas make up a negligible amount of volume of the gas itself. Is this an ok approximation, if so when?

53. Ideal Gas Laws Assumptions 1.) The particles in a gas make up a negligible (unimportant) amount of volume of the gas itself. Good most of the time – atoms in a gas take up less than 1/1000 th of the volume of a gas. What is between the atoms? A neutron star is nearly solid matter, a teaspoon of it would weigh about 10,000,000 tons

54. Ideal Gas Laws Assumptions Generally a good assumption, because the particles are so far apart. 2.) The particles in a gas are not attracted or repelled from each other. good or bad assumption?

55. Ideal Gas Laws Assumptions Good!!!! 3.) Collisions of gas particles are totally elastic. Demo- happy / sad balls If the atoms of gas slowed don’t with each collision, what would happen to the gas in this room? good or bad assumption?

56. Ideal Gas Laws Assumptions Good assumption 4.) Temperature measures the average kinetic energy of the particles of a gas. good or bad assumption? As the temperature of a gas goes up its particles move faster!

57. What did we use in chemistry to talk about the number of atoms in a sample? THE MOLE 1 mole of something = 6.022 x 10 23 pieces of something NANA

58. 1 MOLE of ANY gas at STP has a volume of 22.4 L What if the temperature was greater than 273 K? What if the pressure was greater than 1 atm?

59. PV = nRT Pressure Volume(L) mole Universal Gas Constant Temperature (K) Units must match

60. R = 8.31 J mol K So R (universal gas constant) is equal to kPa L mol K R = 8.31 or This is the standard PHYSICS R to use, there are others based on different unit of pressure.

61. At STP, 1 mole of a gas occupies 22.4 L NO MATTER WHAT THE GAS IS!!! At STP, 1 mole of He has a volume of 22.4 L At STP, 1 mole of CO 2 has a volume of 22.4 L What is different? SF6 boat demo

62. How is it that even though a CO 2 molecule is bigger than a H 2 molecules, the gases occupy the same VOLUME? The particles are so far apart, most of the volume of a gas is NOTHING!

63. PV = nRT Pressure Volume(L) mole Universal Gas Constant Temperature (K) Units must match R = 8.31 kPa L Mol K J or

64. How much space would 3.5 mol of N 2 require at 305 K and 250 torr?

65. If.52 mole of Ar is trapped in a 50 mL syringe at 25 o C, what is the pressure inside the syringe?

66. At what temperature would 8.5 x 10 24 molecules of CO 2 exert a pressure of 193 kPa in a 25.3 L tank?

67. What is the density of N 2 gas at 1 atm and 350 o C?

68. R k =k = NANA Boltzmann’s constant (1.38 x 10 -23 J/K) J mol K R = 8.31 Avag

69. KE = kT 3232 Average kinetic energy of a group of gas particles. Boltzmann’s constant (1.38 x 10 -23 J/K) Temperature (K) Why is this only the average KE of the atoms?

70. 3kT 3232 mv 2 2 rearranging V rms = = kT m Don’t write yet

71. 3kT V rms = m Root mean square velocity of an atom in a gas m/s In Kelvin Mass of atom or molecule in kg 1 amu = 1.6605x10 -27 kg

72. What is the average speed of a nitrogen molecule in this room at a temperature of 25 o C lets find out? Guesses first???