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Crystals

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Crystals

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  1. Crystals

  2. I. Crystals • Rigid bodies in which the particles are arranged in units that form a repeating pattern. • This particle arrangement gives the crystal a definite shape.

  3. A. True Solids • All true solid substances are crystalline • They have a definite melting point • They have flat faces with definite angles • Crystalline solids "cleave" along unit cell lines http://www.minerals.net/mineral/carbonat/calcite/images/12cleave.jpg

  4. B. Amorphous Solids • Non-crystalline solids • Amorphous substances do not have a pattern when they break. Shattered Glass Amorphous Carbon http://phycomp.technion.ac.il/~anastasy/seminar2/amorphous.jpg http://www.sxc.hu/pic/m/n/ni/nickobec/76746_texture_shattered_glass_three.jpg

  5. Which is crystalline? Which is amorphous? Amorphous Crystalline

  6. C. Steno’s Law • All crystals of a substance have the same angle between their faces • An INTRINSIC (or intensive) property—does not depend on amount, size, etc.

  7. Nicolaus Steno—1699 • Discovered Steno’s duct; a duct of the salivary gland • Steno's law of superposition: layers of rock are arranged with the oldest on the bottom and the youngest on the top • Was ordained as a Roman Catholic priest in 1675

  8. D. Forces Holding Crystals Together • Hydrogen Bonds ex: Ice • Van der Waals Forces ex: Sugar • Ionic Bonds ex: NaCl, CaCl2 • Metallic Bonds ex: Fe, Cu, Al

  9. E. Unit Cells • The simplest repeating unit in a crystal • The arrangement of these units is determined by the bond angle between the particles. • Crystals are made up of repeating unit cells • Ex: small & large diamonds have the same shape Salt-NaCl Salt magnified 40 times http://www.scienceclarified.com/images/uesc_03_img0169.jpg http://www.chem.cornell.edu/sl137/Pictures.dir/salt.jpg

  10. Sample Unit Cells Simple Cubic Body Centered Cubic Face Centered Cubic

  11. F. Space Lattice • Three-dimensional arrangement of unit cells repeated over and over giving a crystal its overall geometric shape

  12. Vocabulary a. Solute – the substance dissolved in a given solution b. Solvent – a substance that dissolves another to form a solution. • Water is a solvent for sugar c. Saturated solution - a solution obtained when a solvent (liquid) can dissolve no more of a solute (usually a solid) at a particular temperature

  13. d. Unsaturated solution - a solution in which more solute can be dissolved e. Supersaturated solution - a solution that contains more of the dissolved material than could be dissolved by the solvent under normal circumstances

  14. www.mpcfaculty.net/mark_bishop/supersaturated.htm

  15. Super Saturated Solution Sugar crystals f. Seed Crystal Seed crystal = the initial crystal • With rock candy, need a small sugar crystal to get large candies • With fudge, seed crystals lead to large crystal growth and bad, grainy fudge. http://www.sweetconnections.com/images/rock-candy.jpg

  16. Crystal defect – an impurity in the crystal lattice

  17. II. Vocabulary (continued) h. Hydrated Crystals - Water molecules become chemically bonded to ions in the crystal. • Anhydrous Crystals Crystal without water CuSO4• 5 H2Oa hydrated crystal

  18. Farmers will truck anhydrous ammonia to save the cost of trucking the weight of the water in a hydrated crystal.

  19. j. Desiccant - Anhydrous substances that gain water so easily that they can be used to remove water from other substances. ex: Silica gel packets found in new shoes…

  20. k. Hygroscopic - a solid whose ions capture water molecules out of the air l. Deliquescent - a solid so strongly hygroscopic that it slowly dissolves in air http://images.google.com/imgres?imgurl=http://boomeria.org/chemlectures/crystals/deliquescent.jpg&imgrefurl=http://boomeria.org/chemlectures/crystals/crystals.html&h=401&w=504&sz=115&hl=en&sig2=iV1JdCtiIovAn31pgV0Opw&start=5&tbnid=2k87VM9a7qPD4M:&tbnh=103&tbnw=130&ei=lZT5Rf2qCJquiQH1p8TBBQ&prev=/images%3Fq%3Ddeliquescent%26svnum%3D10%26hl%3Den%26safe%3Dactive

  21. m. Viscosity - the property of a fluid that resists the force tending to cause the fluid to flow. (how “sticky” a liquid is)

  22. How does Temperature Affect Viscosity?

  23. III. Dissociation Review Na+ (aq) + Cl-(aq) NaCl(s)  ___ moles of solute CaBr2 (s)  ___ moles of solute Mg3(PO4)2 (s)  ___ moles of solute C6H12O6 (s)  ___ moles of solute 2 Ca+2 (aq) + 2 Br-1 (aq) IONIC 3 3 Mg+2 (aq) + 2PO4-3 (aq) 5 C6H12O6 (aq) COVALENT 1

  24. IV. Freezing Pt Depression & Boiling Pt Elevation FACT: 1 mole of solute per liter of water lowers the freezing point by And Increases the boiling point by 1.86o C 0.51o C

  25. b. Why do solutes reduce the freezing point? • solute interferes with formation of space lattice.

  26. P atm t = 1 min c. Why do solutes increase the boiling point? • solute lowers the vapor pressure, harder to boil. Pvap

  27. Examples: 20.00 g of MgCl2 is dissolved in 100 ml of water. What is the change in boiling & freezing points? MgCl2 Mg+2+ 2 Cl-1 # solute particles? 3 0.21 mol MgCl2 x 3 mol solute = 0.63 mol of solute particles in 100 ml water

  28. Real Life Examples • Why do we use salt on roads? • To decrease the freezing point • Which is better, NaCl or CaCl2? • CaCl2 3 particles of solute • Is sugar a good de-icer? • NO! Only 1 particle of solute

  29. Why use antifreeze in your car? • To keep water in radiator from freezing • Freezing water will crack radiatorIce expands as it freezes • To keep water in radiator from boiling

  30. Homemade ice cream • You add salt to the ice to decrease its temperature allowing the cream to freeze more easily, quickly with fewer large crystals  grainy ice cream

  31. FP/BP Quiz 5.0 g Na2SO4 is dissolved in 100 ml of water. 1) Calculate the grams of Na2SO4 in 1000 ml H2O 2) Calculate the moles of Na2SO4 in 1000 ml H2O 3) Write the dissociation equation and determine the moles of solute in 1000 ml H2O Na2SO4 2Na+ + SO42- 0.35 mol  1.05 mol solute 4) Calculate DTFP (Freezing Point Depression) 5) Calculate the new Boiling Point

  32. Antifreeze Sample Problem A sample of antifreeze contains 100 mol of ethylene glycol (covalent) in 5 L of water. Calc the FP & BP. • FP • BP New freezing point? -37.2 oC (-35oF) New boiling point? 110.2 oC (230oF)

  33. Ice Cream Sample Problem What mass of rock salt is needed in 1 L of water to lower the freezing point to -10oC? Freezing Point depression? How many moles of solute are needed? Dissociation Eqn? How many moles of NaCl? grams? NaCl  Na+ + Cl- 10oC 1:2 5.4 moles solute 2.7 moles

  34. V. Hydrated Crystals • Ex: CuSO4 • 5H2O + heat CuSO4 + 5 H2O (Blue) (White) Hydrate Anhydrous Hydrate

  35. Hydrates – crystals with water • Anhydrous – crystal with no water • Water of Hydration: 1) The amount of water in a crystal 2) Water of hydration is a definite ratio FeSO4  3 H2O MW = __________ 55.8 + 32.1 + 4(16.0) + 3 (18) = 189.9 g/mol

  36. Naming: • 1 H2O monohydrate • 2 H2O dihydrate • 3 H2O trihydrate • 4 H2O tetrahydrate • 5 H2O pentahydrate • 6 H2O hexahydrate • 7 H2O heptahydrate • 8 H2O octahydrate • 9 H2O nonahydrate • 10 H2O decahydrate

  37. Problem Solving 1) Find the % H2O in Sodium Sulfide trihydrate. Na2S • 3H2O

  38. Problem Solving 2) If 10 grams of Na2S  3 H2O is heated ______ grams of water will be lost. (40.9% water) 3) 1 mole of Na2S combines with ___ moles of H2O? 0.409 x 10.0 = 4.09 g of water lost 3 Na2S • 3H2O The ratio is 1 to 3

  39. Problem Solving 4) If 0.03 moles of CuSO4 is combined with 0.15 moles water, what is the formula? name? 5) If 0.04 mol of BeCl2 is combined with 0.08 mol water, what is the formula? The ratio is 1 to 5 CuSO4• 5H2O Copper (II) sulfate pentahydrate The ratio is 1 to 2 BeCl2• 2H2O Beryllium chloride dihydrate

  40. Problem Solving 3.94 g CuCl2 i. mass of anhydrous crystal? ii. moles of anhydrous crystal? iii. moles of water? iv. experimental mole ratio v. formula of hydrated crystal? vi. name of hydrated crystal? 6) Five grams of hydrated CuCl2 crystals lose 1.06 g of water when heated. 1 to 2 ratio CuCl2• 2H2O Copper (II) chloride dihydrate

  41. VII. Allotropes • Any of several crystalline forms of a chemical element. Ex. Charcoal, graphite, and diamond are all allotropes of carbon

  42. Sulfur • S8 2 crystalline forms: rhombic & monoclinic • Sx 1 amorphous form: brown, plastic sulfur • Formed by rapid cooling • Will crystallize over time

  43. White phosphorous shells Phosphorous White Phosphorous Video (skip to the middle) http://video.google.com/videoplay?docid=1124770688802666702

  44. Carbon • Graphite – 2 dimensional bonding • VdW's forces between layers • brittle, breaks in layers • Diamond – 3 dimensional bonding • Hard and Durable • Fullerenes – C60 C70

  45. Eight common allotropes of carbon Diamond Graphite Bucky ball Nanotube http://upload.wikimedia.org/wikipedia/commons/thumb/f/f8/Eight_Allotropes_of_Carbon.png/333px-Eight_Allotropes_of_Carbon.png

  46. What is the difference in bonding between Graphite and Diamond? • Three dimensional bonding in diamond, only two dimensional in graphite

  47. Oxygen • O2 “normal” oxygen in the air we breathe. • O “nascent oxygen” –very reactive • O3 ozone— A thin layer in the upper atmosphere’ reflects UV light back into space.

  48. Ozone: The Good, The Bad, & the Ugly • Good: protects us from harmful UV rays • By banning CFC’s that destroy atmospheric ozone we’ve decreased the holes in the ozone layer.

  49. “Ozone action days” • Weather conditions are favorable for ground-level ozone (smog) to reach unhealthy levels within our region, and your voluntary actions are requested. Please help and make a difference on this OZONE ACTION DAY by doing any of the following: • Car pool or use mass transit when possible • Bike to work • Refuel automobiles later in the evening • Postpone lawn mowing until the evening • Postpone using paints, lacquers and solvents until late in the afternoon • Reduce or postpone, when possible, industrial processing activities which produce VOC emissions • Reduce your demand for electricity