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Phases of Matter

Phases of Matter. Solid to liquid to gas and back again. Particle Motion. Particle Size. Gases consist of small particles separated by empty space Volume of particles small compared w/volume of empty space

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Phases of Matter

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  1. Phases of Matter Solid to liquid to gas and back again

  2. Particle Motion Particle Size Gases consist of small particles separated by empty space Volume of particles small compared w/volume of empty space Because gas particles far apart, no significant attractive/repulsive forces (there is though) • Gas particles in constant, random motion • Move in straight line until collision w/other particles or container walls • Collisions between particles elastic(inelastic) • KE transferred between particles, but total KE does not change (lost as heat) http://college.hmco.com/chemistry/shared/media/animations/visualizingmolecularmotion.html http://college.hmco.com/chemistry/shared/media/animations/visualizingmolecular.html

  3. Particle energy • Velocity reflects both speed and direction of motion • All particles have same mass but not same velocity • All particles do not have same kinetic energy • Kelvin T scale that starts at zero (Absolute zero: all atomic thermal motion is stopped/-273.15oC/0 K) • If T (in K) of gas doubles, KE of particles in gas doubles • If T ↓by 1/3, KE ↓by 1/3 Temperature: average KE of molecules Heat energy =total KE of atoms KE = ½ mv2 http://college.hmco.com/chemistry/shared/media/animations/visualizingmolecularmotion.html http://college.hmco.com/chemistry/shared/media/animations/visualizingmolecular.html

  4. Diffusion: Spreading out from concentrated source-result in increase in entropy of substance • Random movement allow separation of molecules • Greater space, greater ability to spread out • More packed, less space, harder to diffuse • What affects speed/rate of diffusion? • Diffusion rate directly proportional to average speed of molecules • Faster molecules diffuse at faster rate • Molar masses • Heavier gases diffuse more slowly

  5. Solids More tightly packed Slower diffusion Liquids Less packed/move more freely Faster diffusion Gases Distant from one another Fastest diffusion

  6. Effusion: movement through very tiny opening into region of lower pressure Effusion Diffusion

  7. Diffusion- direction of gas movement • Effusion - direction/rate of gas movement • Rate of effusion/diffusion inversely proportional to of mass • Consider KE = ½ mv2 • Two bodies of unequal mass w/same KE, lighter one moves faster • Two gases at same T, one w/lower molecular mass diffuses faster http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/animations/Effusion2.html

  8. Let's compare rate off effusion of two common gases: N2 has molecular mass of 28.0 g. O2 has molecular mass of 32.0 g. • RateN2/RateO2 = 32.0 g / 28.0 g. • RateN2/RateO2 = 1.069 • Tells us N2 is 1.07x as fast as O2-faster, not by much • Find molecular mass. Let's use gas A and B. A is 0.68 times as fast as B. The mass of B is 17 g. What is the mass of A? • 0.68 = 17 g/Mass A • Square both sides: 0.4624 = 17 g/Mass A • Solve for Mass A – Mass B = 17 g/0.4624 = 36.7647 g • 37 g plugged into formula to check answer. (gases used-A is HCl and B is NH3). http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/gaslaw/effusion_macro.html

  9. Effusion • Moisten a piece of blue litmus paper and transfer it (using glass rod) to the bottom of the tallest graduated cylinder available. • Place the cylinder on its side and insert a cotton ball saturated with concentrated HCL at the mouth of the cylinder and start your stopwatch. • Immediately seal the cylinder with a rubber stopper and record the distance between the cotton ball and the litmus paper. • Watch the litmus paper and record the time at which it BEGINS to change color. • Determine the diffusion rate of HCl gas (rHCl) by dividing the distance by the time. • Repeat the process using red litmus paper and a cotton ball soaked in ammonia. • Determine the diffusion rate of ammonia (rNH3) by dividing the distance between the ammonia-soaked cotton ball and the red litmus paper by the time required for the litmus paper to begin to turn color. • Which molecule diffused more rapidly? • Is this what you expected?

  10. Use a piece of glass or Plexiglas tubing with an inner diameter greater than 1 cm and a length greater than 50 cm. • Shorten and fasten cotton swabs to the inner surfaces of two one-holed stoppers. • Apply concentrated HCl to one what using a dropper and ammonia to the other. • Insert the two stoppers in the tube at the same time. • The ammonia and HCl molecules will diffuse at different rates depending upon their molecular weights. • When ammonia molecules contact hydrogen chloride molecules, white salt ammonia chloride forms. • Record the distance between the ring and both sources. • Which molecule is smaller? Explain. • Using Graham’s Law of Diffusion, calculate the theoretical ratio of different rates of ammonia to hydrogen chloride. • What is the relative error of the ratio of diffusion rates you computed to the theoretical value?

  11. AbbreviationsConversions • atm – atmosphere K = °C + 273mm • Hg - mm Hg 1 cm3 = 1 mL • torr = mm Hg 1 dm3 = 1 L = 1000 mL • Pa - Pascal (kPa) Standard Conditions • K - Kelvin 0.00 °C = 273 K° • C - degrees Celsius 1.00 atm = 760.0 mm Hg = 101.325 kPa = 101,325 Pa

  12. 136. If equal amounts of helium and argon are placed in a porous container and allowed to escape, which gas will escape faster and how much faster? • 137. What is the molecular weight of a gas which diffuses 1/50 as fast as hydrogen? • 138. Two porous containers are filled with hydrogen and neon respectively. Under identical conditions, 2/3 of the hydrogen escapes in 6 hours. How long will it take for half the neon to escape? • 139. If the density of hydrogen is 0.090 g/L and its rate of diffusion is 6 times that of chlorine, what is the density of chlorine? • 140. How much faster does hydrogen escape through a porous container than sulfur dioxide?

  13. Is substance solid, liquid, or gas? If KE > attractive forces, substance will not condense into liquid/solid Overcomes attractive forces between them Gas molecules move freely Take size/shape of container If KE < attractive forces, liquid/solid will form Attractive forces hold particles close Molecules do not move apart

  14. Pressure:force per unit area • Gas particles all moving about randomly, collide w/container walls • Each collision produces tiny force on wall but since there are 1023 gas particles in liter container, there is lot of pressure • Gas particles move in every direction so they exert pressure in all directions (atmospheric pressure)

  15. Water weighs more/exerts much more pressure At sea level @25oC: 1 atm 1 atm = 760 mm Hg = 29.92 inches Hg 1,013.25 millibars (pascals) = 101.325 kPa = 760mm Hg = 760 torr = 14.7 psi

  16. PV =nRT

  17. 0.875 atm to mm Hg: • 0.875 atm 760.0 mm Hg = 665 mm Hg 1 atm • 745.0 mm Hg to atm: • 745.0 mm Hg 1atm = 0.980 atm 760 mm Hg • 0.955 atm to kPa: • 0.955 atm 101.325 kPa = 96.77 kPa 1 atm

  18. 98.35 kPa to atm: 98.35 kPa 1 atm 101.325 kPa = 0.970 atm 740.0 mmHg to kPa: 740.0 mm Hg 101.325 kPa = 98.66 kPa 760.0 mm Hg 99.25 kPa to mmHg: 99.25 kPa 760.0 mm Hg = 744.4 mm Hg 101.325 kPa

  19. Dalton’s Law of Partial Pressures • Gases cannot interact with each other. http://www2.wwnorton.com/college/chemistry/gilbert/tutorials/interface.swf?chapter=chapter_08&folder=daltons_law

  20. Mole fraction related to Dalton’s Law • 2 moles of H and 4 moles of O in 5 liter vessel at 300 K, P = 29.6 atm • Calculate mole fractions • H2 mole fraction = 2 moles/6 moles = 0.333 • O2 mole fraction = 4 moles/6 moles = 0.667 • Calculate partial pressures • PH2 = Ptotal x 0.333 = 29.6 atm x 0.333 = 9.9 atm • PO2 = Ptotal x 0.667 = 29.6 atm x 0.667 = 19.7 atm

  21. Most common use of Dalton's Law is with water vapor (Ptotal = Pgas + Pwater vapor) Example: 0.750 L of a gas is collected over water at 23.0°C with a total P of 99.75 kPa. What is the P of the dry gas? 99.75 kPa = 2.8104 + x x = 97.57 kPa

  22. 65. A container holds three gases: oxygen, carbon dioxide, and helium. The partial pressures of the three gases are 2.00 atm, 3.00 atm, and 4.00 atm, respectively. What is the total pressure inside the container? • 66. A container with two gases, helium and argon, is 30.0% by volume helium. Calculate the partial pressure of helium and argon if the total pressure inside the container is 4.00 atm. • 67. If 60.0 L of nitrogen is collected over water at 40.0 °C when the atmospheric pressure is 760.0 mm Hg, what is the partial pressure of the nitrogen? • 68. 80.0 liters of oxygen is collected over water at 50.0 °C. The atmospheric pressure in the room is 96.00 kPa. What is the partial pressure of the oxygen?

  23. 69. A tank contains 480.0 grams of oxygen and 80.00 grams of helium at a total pressure of 7.00 atmospheres. Calculate the following. • a) How many moles of O2 are in the tank? • b) How many moles of He are in the tank? • c) Total moles of gas in tank. • d) Mole fraction of O2. • e) Mole fraction of He. • f) Partial pressure of O2. • g) Partial pressure of He.

  24. 70. A tank contains 5.00 moles of O2, 3.00 moles of neon, 6.00 moles of H2S, and 4.00 moles of argon at a total pressure of 1620.0 mm Hg. Complete the following table • O2 Ne H2S Ar Total Moles 18.00 Mole fraction 1 Pressure fraction 1 Partial Pressure 1620.0 • 71. A mixture of 14.0 grams of hydrogen, 84.0 grams of nitrogen, and 2.0 moles of oxygen are placed in a flask. When the partial pressure of the oxygen is 78.00 mm of mercury, what is the total pressure in the flask? • 72. A flask contains 2.00 moles of nitrogen and 2.00 moles of helium. How many grams of argon must be pumped into the flask in order to make the partial pressure of argon twice that of helium?

  25. Homework: • Read 13.1, pp. 385-392 • Q pp. 414-415, #32-33, 62, 63, 65, 67, 70, 71, 76

  26. Intramolecular forces (forces holding individual molecules together/covalent bonds, ionic bonds or metallic bonds) (forces between molecules) Forces between covalent molecules • Hydrogen • Dipole-dipole interactions • Dispersion forces • van der Waals forces (weakest attractions)

  27. London Dispersion Forces (induced dipole - induced dipole attraction)weakest of all molecular interactions Causes them to condense to liquids/ freeze into solids when temperature lowered sufficiently Only force between nonpolar molecules (H2/Cl2/CO2/CH4) electrostatic attraction

  28. Dipole - Induced Dipole Forces nonpolar induced dipole Polar

  29. http://college.hmco.com/chemistry/shared/media/animations/uc-imfdipoledipole.htmlhttp://college.hmco.com/chemistry/shared/media/animations/uc-imfdipoledipole.html Dipole (or dipole-dipole) Interactions (water)

  30. Hydrogen Bondsstrongest force between covalent molecules Water has simple molecular structure: 104.5o Charges don’t cancel

  31. http://college.hmco.com/chemistry/shared/media/animations/imfhydrogenbondingforces.htmlhttp://college.hmco.com/chemistry/shared/media/animations/imfhydrogenbondingforces.html • Last only fraction of second • Constantly form/break • Strong enough to bind water molecules together • H covalently bonded to F/O/N (very EN) • ~1/20 strength of covalent bond • Give water unique character

  32. H bonds in water exert significant attractive force Cohesion: between like particles Adhesion: between unlike substances Capillarity: water molecules go upward through narrow tubes (roots  leaves) against pull of gravity

  33. Ion-Induced Dipole Forces

  34. Homework: Read 13.2, pp. 393-395 Q, pp. 414-416, # 36-38, 41, 75

  35. The Nature of Liquids • Weak attractive forces • Condensed states of matter (liquids/solids) • ↑ P on liquids hardly affects V • KE < intermolecular forces • Liquid particles vibrate and spin in fixed positions while rolling and sliding over one another

  36. Fluidity(liquids/gases are fluids) Ability to flow Intermolecular attractions interfere with flow Viscosity Resistance to flow Particle closeness slow movement as they flow past one another Determined by intermolecular forces, particle shape, temperature

  37. Many physical properties are determined by motions and attractive forces • Evaporation: liquid  gas • Vaporization: liquid  vapor below BP • Vapor: normally liquids, but evaporate at room T/P • Water, gasoline, rubbing alcohol, polish remover (ethyl acetate)

  38. Surface Tension:measure of how difficult it is to stretch/ break liquid’s surface No net pull in any one direction • Molecules inside drop attracted in all directions • Drops on surface attracted to sides/inward into sphere-shape, w/smallest surface area for given volume • Higher surface tension, more nearly spherical drop • Surface tension water > all other liquids except Hg

  39. Wetting agent: soap/detergent w/long C/H chains reduces by ~1/3 original strength Surfactants: reduces surface tension by moving to surface of water Water stretched into thin sheets, to form bubbles (combination of two fluids/ liquid surrounding gas) Lower surface tension by adding:

  40. Surface Tension and Vortex • Fill one flask half-full with isopropyl alcohol and stopper it. Fill the other half-full with water. (use finely ground pepper to see movement better) • Swirl each flask and record the time until the vortex can no longer be seen. • Which liquid appears to have greater surface tension and greater intermolecular forces? • Which liquid, isopropyl alcohol or water, do you think will boil more easily? Why?

  41. Surface tension and droplet shape • Using an eyedropper or pipet, transfer one drop of water, isopropyl alcohol, others to sheet of wax paper. • Which liquid appears to have the greatest surface tension and the greatest intermolecular forces? Explain.

  42. Surface tension and wetting agents • Use vegetable holder to show how adding detergent to water affects its surface tension. • Why did the holder not float after the detergent was added?

  43. Ice Floats: • Water expands when freezes from 4-0°C and contracts when heated from 0-4°C • Water reaches its maximum density at 4°C • Ice is less dense than water • Most other substances contract when cooled (exceptions also include bismuth and antimony)

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