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Unless otherwise stated, all images in this file have been reproduced from: Blackman, Bottle, Schmid, Mocerino and Wille, Chemistry , 2007 (John Wiley)      ISBN: 9 78047081 0866 . CHEM1002 [Part 2]. Dr Michela Simone Weeks 8 – 13 Office Hours: Monday 3-5, Friday 4-5

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  1. Unless otherwise stated, all images in this file have been reproduced from: Blackman, Bottle, Schmid, Mocerino and Wille,Chemistry, 2007 (John Wiley)     ISBN: 9 78047081 0866

  2. CHEM1002 [Part 2] Dr Michela Simone Weeks 8 – 13 Office Hours: Monday 3-5, Friday 4-5 Room: 412A (or 416) Phone: 93512830 e-mail:michela.simone@sydney.edu.au

  3. Summary of Last Lecture • Entropy • Energy change is not an indicator of direction of change • Naturally occurring processes tend towards greater dispersal of energy • Many exothermic reactions occur naturally • Exothermic reactions disperse energy into the surroundings • Exothermic reactions are favoured at low T • Endothermic reactions can only occur if they lead to an increase in entropy • Endothermic reactions are favoured at high T

  4. When one mole of ice melts to liquid at 0 °C, The entropy of the system decreases The entropy of the system remains the same The entropy of the system increases The order of the system increases None of the above Practice Examples - 1

  5. The entropy of a chemical system will usually increase when A molecule is broken into two or more smaller fragments A reaction results in an increase in the moles of gas A solid changes to a liquid A liquid changes into a gas All of the above Practice Examples - 2

  6. Crystal Structures I • Lecture 8: • Close packing: hexagonal vs cubic close packing • Unit cells • Non-close packing: body centred and simple cubic packing • Blackman Chapter 7, Section 7.4 (pages 259-265) • Lecture 9: • Packing efficiency • Octahedral and tetrahedral interstitial holes • Ionic crystal structures • Blackman Chapter 7, Section 7.4 (pages 265-268)

  7. How many elements in the Periodic Table exist as liquids at room temperature and pressure? 1 2 11 13 20 How Important Are Solids – 1? 30

  8. How many elements in the Periodic Table exist as gases at room temperature and pressure? 1 2 11 13 20 How Important Are Solids – 1? 30

  9. Periodic Table by Standard State 88% 2% 10%

  10. Metals - Packing of Spheres Close-packed hexagonal array Cubic array each atom has 4 nearest neighbours each atom has 6 nearest neighbours Hexagonal array has more efficient packing

  11. Close Packed Structures • cubic closed packingCCP • hexagonal closed packingHCP layers repeat in the sequence: layers repeat in the sequence: A B C ABCABCABC A B A BABAB

  12. Unit Cells A unit cell is the simplest building block which when repeated in three-dimensions generates the structure of the crystal.

  13. Unit Cell for Cubic Close Packed • The unit cell for CCP is face centred cubic (FCC) • atoms on each corner and atoms on each face of the cube

  14. Other Metal Structures • body centred cubic (BCC) • atoms at the cornersand centre of cube • simple cubic • atoms at the cornersof cube

  15. How many whole atoms are there in the BCC unit cell? 1 2 8 9 How Many Atoms in the BCC Unit Cell? • atoms at the cornersand centre of cube 29

  16. Summary: Crystal Structures I • Learning Outcomes - you should now be able to: • Complete the worksheet • Describe how the layer structures of hexagonal and cubic-close packed structures differ • Describe the face-centred cubic unit cell and show how it relates to the layer structure for CCP • Next lecture: • More on crystal structures

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