Kinetic Molecular Theory of Gases

1. <?xml version="1.0"?><AllQuestions /> <?xml version="1.0"?><Settings><answerBulletFormat>Numeric</answerBulletFormat><answerNowAutoInsert>No</answerNowAutoInsert><answerNowStyle>Explosion</answerNowStyle><answerNowText>Answer Now</answerNowText><chartColors>Use PowerPoint Color Scheme</chartColors><chartType>Horizontal</chartType><correctAnswerIndicator>Checkmark</correctAnswerIndicator><countdownAutoInsert>No</countdownAutoInsert><countdownSeconds>10</countdownSeconds><countdownSound>TicToc.wav</countdownSound><countdownStyle>Box</countdownStyle><gridAutoInsert>No</gridAutoInsert><gridFillStyle>Answered</gridFillStyle><gridFillColor>0,0,0</gridFillColor><gridOpacity>100%</gridOpacity><gridTextStyle>Keypad #</gridTextStyle><inputSource>Response Devices</inputSource><multipleResponseDivisor># of Responses</multipleResponseDivisor><participantsLeaderBoard>5</participantsLeaderBoard><percentageDecimalPlaces>0</percentageDecimalPlaces><responseCounterAutoInsert>No</responseCounterAutoInsert><responseCounterStyle>Oval</responseCounterStyle><responseCounterDisplayValue># of Votes Received</responseCounterDisplayValue><insertObjectUsingColor>Blue</insertObjectUsingColor><showResults>Yes</showResults><teamColors>User Defined</teamColors><teamIdentificationType>None</teamIdentificationType><teamScoringType>Voting pads only</teamScoringType><teamScoringDecimalPlaces>1</teamScoringDecimalPlaces><teamIdentificationItem></teamIdentificationItem><teamsLeaderBoard>5</teamsLeaderBoard><teamName1></teamName1><teamName2></teamName2><teamName3></teamName3><teamName4></teamName4><teamName5></teamName5><teamName6></teamName6><teamName7></teamName7><teamName8></teamName8><teamName9></teamName9><teamName10></teamName10><showControlBar>Slides with Get Feedback Objects</showControlBar><defaultCorrectPointValue>100</defaultCorrectPointValue><defaultIncorrectPointValue>0</defaultIncorrectPointValue><chartColor1>187,224,227</chartColor1><chartColor2>51,51,153</chartColor2><chartColor3>0,153,153</chartColor3><chartColor4>153,204,0</chartColor4><chartColor5>128,128,128</chartColor5><chartColor6>0,0,0</chartColor6><chartColor7>0,102,204</chartColor7><chartColor8>204,204,255</chartColor8><chartColor9>255,0,0</chartColor9><chartColor10>255,255,0</chartColor10><teamColor1>187,224,227</teamColor1><teamColor2>51,51,153</teamColor2><teamColor3>0,153,153</teamColor3><teamColor4>153,204,0</teamColor4><teamColor5>128,128,128</teamColor5><teamColor6>0,0,0</teamColor6><teamColor7>0,102,204</teamColor7><teamColor8>204,204,255</teamColor8><teamColor9>255,0,0</teamColor9><teamColor10>255,255,0</teamColor10><displayAnswerImagesDuringVote>Yes</displayAnswerImagesDuringVote><displayAnswerImagesWithResponses>Yes</displayAnswerImagesWithResponses><displayAnswerTextDuringVote>Yes</displayAnswerTextDuringVote><displayAnswerTextWithResponses>Yes</displayAnswerTextWithResponses><questionSlideID></questionSlideID><controlBarState>Expanded</controlBarState><isGridColorKnownColor>True</isGridColorKnownColor><gridColorName>Yellow</gridColorName><AutoRec></AutoRec><AutoRecTimeIntrvl></AutoRecTimeIntrvl><chartVotesView>Percentage</chartVotesView><chartLabelsColor>0,0,0</chartLabelsColor><isChartLabelColorKnownColor>True</isChartLabelColorKnownColor><chartLabelColorName>Black</chartLabelColorName><chartXAxisLabelType>Full Text</chartXAxisLabelType></Settings> <?xml version="1.0"?><AllAnswers /> Kinetic Molecular Theory of Gases These ideas have withstood the test of time and much experimentation.

2. Six Postulates of the Kinetic Molecular Theory of Gases A scientific postulate is a statement assumed to be true unless proven otherwise.

3. Kinetic Molecular Theory • Important for explaining the behavior of molecules in matter. • All matter is made up of moving particles too small to be seen even with the strongest microscope.

4. Kinetic • Is Latin for motion Kinetic Molecular theory helps explain the physical and behavior properties of gases. The motion of particles can be affected by variables and these variables are important part of kinetic theory.

5. Six Postulates • A gas consists of very small particles, each of which has a mass. Example: An inflated basketball weighs more than a deflated basketball.

6. Six Postulates • The distances separating gas particles are relatively large. The volume of the gas particles is assumed to be zero because it is negligible compared with the total volume in which the gas is contained. This is a fair assumption.

7. Six Postulates 3. Gas particles are in constant, rapid, random motion. They move in straight lines in within their container Gases immediately fill a container and quickly diffuse from one area to another. This is a good description of how gas molecules behave

8. Six Postulates • Collisions of gas particles with each other or with the walls of the container are perfectly elastic. Elastic collisions means that no energy is lost or gained. Unlike “bouncing balls,” no energy of motion is lost.

9. Six Postulates • The average kinetic energy of gas particles depends only on the temperature of the gas. The kinetic energy of gas molecules is proportional to their temperature in Kelvins -- a good description. KE = mv2 / 2 High T  Higher KE Low T  Lower KE

10. Six Postulates 6. Gas particles exert no force on one another. Attractive forces between gas particles is assumed to be zero. Gas particles do not slow down and condense into a liquid because they exert only very weak attractive forces upon each other. Gas molecules don’t interact with one another. Depending on the gas, this can be good or bad assumption. H2O vapor has much stronger intermolecular interactions than He.

11. Measuring Variables • Pressure is measured in atmospheres (atm) • Temperature is measured in Kelvin. Room temp. is approx. 300K

12. Conversion • C = (5/9) x (f-32) • K = C + 273 • C= celsius • F= farhenheit • K = Kelvin

13. Check your understanding

14. Relationships • When temperature increases, the speed of particles increase (direct relationship) • When the temperature decreases the speed of the particles decreases (direct relationship)/

15. Equation • KE = ½ mv2 • Two factors determine kinetic energy • M= mass • V= speed

16. Real Gas -- Ideal Gas Very high temperatures and very low pressure help real gases simulate ideal gases. @ High Temperatures: Gas molecules move so quickly that there is not time to interact. @ Low Pressure: Gas molecules don’t encounter each other very often.

17. Think- Pair- Shair • What is an ideal gas law?

18. Avogadro’s Principle When measured at constant temperature and pressure, equal volumes of gases contain equal numbers of moles.

19. Avogadro’s Principle • The volume of a gas is directly proportional its number of moles (n), regardless of the identity of the gas V n

20. V n • Ideal gas molecules don’t have volume, molecule size doesn’t matter • Ideal gases don’t interact with each other, no intermolecular forces change the volume of the gas

21. V n Therefore… Ideal gas molecules behave according to Avogadro’s Principle.

22. Standard Temperature & Pressure STP • 1 atmosphere pressure (atm) • 273 Kelvin (K) or 0 0C

23. Standard Molar Volume • The volume occupied by one mole of gas at STP • 22.4 L

24. States of Matter • Solid • Liquid • Gas

25. Consequences of KMT • Most gases are ideal and will follow these rules. The only conditions under which these assumptions fail is when the gas sample is either under high pressure or at low temperatures.

26. Consequences of KMT • High Pressure- rule #2 fails the gas will condense to a liquid. • Low temperature- rule #4 fails the molecules move slow enough that they attract and the will condense to a liquid.

27. Think- Pair -Share • How could kinetic energy help you explain why you can smell a cake that is baking in the kitchen when you are in your bedroom?

28. Think – Pair- Shair • Would it make a difference if it were a hot or cold day? Why or why not?

29. Check your Understanding • If we have a closed rigid gas container and we inject more gas into the container, what will happen to the internal pressure of the container? Explain your answer

30. Check your understanding • If we have a closed rigid container and we raise the temperature of the container, what will happed to the internal pressure of the container? Explain your answer.

31. Real World Application • How can a small propane tank hold enough to cook with all summer?

32. Day 2: Review • Gas contain particles that are in straight, random, motion • Gas particles collide with each other and the wall… these collisions are elastic • Gas particles spread out, so they don’t take up space • Gas particles are NOT attracted to each other

33. Day 2 : Review • The variables involved are pressure, volume, temperature, and # and size of particles.

34. Day 2: Demonstration and Disscussion

35. Discussion Questions for Demonstration • If you increase the temperature of the flask, what do you predict will happen to the pressure in the balloon?

36. Discussion Questions for Demonstration • If the pressure of the gas increases, would it push harder or softer against the walls?

37. Balloon---- increase temperature, # of particles is constant, what happens to the pressure inside the balloon?

38. If you could increase the number of particles, what would happen to the pressure in the balloon?

39. Demonstration • Balloon and flask on a hot plate

40. What is pressure? • Pressure is the amount of force applied over a surface. • Gas molecules can apply pressure on the walls of a container.

41. Real World Application • To apply pressure on a wound; to apply pressure on a wall, water pressure; shake up a coke bottle… the bottle becomes harder because you’ve increased the pressure inside the bottle. HOW??

42. Internal vs.. External Pressure • Pressure is measured in atm Complete worksheet for a grade

43. Day 3: Diffusion • Diffusion: the random motion of the gas particles causes the gas to mix until they are evenly distributed. • Movement is from high concentration to low concentration

44. Avogrado’s Hypothesis • Equal volumes of gases at the same temperature and pressure contain equal numbers of particles. { Particles in a gas are very far apart, with nothing but space in between. Thus, a collection of relatively large particles does not require much more space then the same number of relatively small particles}

45. Rate of Diffusion • Rate of diffusion is related to the density of the gas

46. Effusion • Effusion is a process related to diffusion. During effusion, a gas escapes through a tiny opening. • Inverse relationship between effusion rates and molar mass.

47. Graham’s law of Effusion • States that the rate of effusion for a gas is inversely proportional to the square root of its molar mass

48. Graham’s Law of Effusion Equation

49. Check your Understanding • Explain why the rate of diffusion depends on the mass of the particles?

50. Diffusion Equation