What changes about the atoms in a substance as it gets warmer?

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 (oC) – based on water Kelvin (K) – based on absolute Zero

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

4. 273 K = oC +

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

10. 3 ways to increase pressure of a gas inside a container: Add more gas because…. 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 Force Pressure = Area What is the force on 1 in2 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 in2 The spheres have an area of about 11 in2 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 thickness of the line How far out from the earth would 99% of all the atoms in the atomosphere be? The radius of the earth is 4,000 miles 99% of the atoms in the atmosphere are within 19 miles

18. How much would the air in this room weigh? The volume of the room is about 10*30*20 = 6000 m3 The density of air (at ground level) is 1.25 kg/m3 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 760 mm Hg How can air pressure pushing down hold up a liquid?

24. Inventor of the barometer Evangelista Torricelli 1608-1657

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 Height of a column of liquid or Area psi 1 ATM = 14.7 101.35 kPa - kilopascal mm Hg 760 760 Torr 29.92 in Hg

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

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. Boyle’s Law P1 V1 = P2 V2 Initial Pressure Final Pressure Initial Volume Final Volume P1 & P2 CAN HAVE ANY UNITS but they must match V1 & V2 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 What would the volume of a 6 L balloon be if I doubled its temperature? (at a constant pressure)

43. Charles’ Law V1 V2 = T1 T2 Final Volume Initial Volume Final Temperature (K) Initial Temperature (K) V1 & V2 must have the same units T1 & T2 MUST BE IN KELVIN

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 Temperature Pressure Assuming that ….

47. P1 P2 = T1 T2 Final Pressure Initial Pressure Final Temperature (K) Initial Temperature (K) P1 & P2 must have the same units T1 & T2 MUST BE IN KELVIN

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 oC to 300 oC?

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