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SCHOLARSHIP WORKSHOP

SCHOLARSHIP WORKSHOP. 2010. Stepping up to Scholarship. The Exam. Structure of the paper Nature of the question. Problem solving Knowledge of practical techniques. Chemical literacy Planning. Some ‘Scholarship’ Skills. Some things to consider.

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SCHOLARSHIP WORKSHOP

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  1. SCHOLARSHIP WORKSHOP 2010

  2. Stepping up to Scholarship The Exam Structure of the paper Nature of the question Problem solving Knowledge of practical techniques Chemical literacy Planning Some ‘Scholarship’ Skills Some things to consider

  3. Scholarship: Chemistry Performance Standard • ●integrate and apply knowledge, principles and skills from different areas of chemistry • ●analyse and interpret information • ●integrate and apply knowledge, principles and skills from different areas of chemistry • ●analyse and interpret information • ●consistently demonstrate a depth and breadth of knowledge, together with insight into the application of chemical principles • ●interpret information and apply knowledge, principles and skills of chemistry Outstanding Scholarship

  4. The Examination Look for resources at www.nzqa.govt.nz

  5. Exam Structure Mark Criteria • 3 – 6 questions • 8 marks per question • 7 - 8 outstanding performance • 5 - 6 scholarship performance • 3 - 4 demonstrates understanding • 1 - 2 meagre understanding relevant to the topic Note: 2004 & 2005 papers organised differently

  6. Knowledge Base Level 2 and Level 3 Chemistry

  7. The Best Performing Candidates most commonly demonstrated the following skills and/or knowledge: • read and interpreted questions correctly • wrote logical and coherent responses and showed some evidence of planning and linked their knowledge of chemistry directly to the context of the question asked • correctly used chemical vocabulary and defined terms when necessary • wrote answers that were supported by balanced equations and / or correct formulae • presented accurate calculations, showed working clearly and used significant figures appropriately.

  8. showed some evidence of practical laboratory work and an understanding of the procedures used • showed an accurate and detailed understanding of chemical concepts • applied their knowledge in unfamiliar settings • were familiar with all the Level 3 and related Level 2 Achievement Standards • showed an accurate and detailed understanding of chemical concepts particularly in relation to atomic properties and intermolecular forces • able to retrieve data that was presented in an unfamiliar form and use it to solve problems or explain given scenarios

  9. Common Areas of Difficulty: Turn to your neighbor and discuss what you think the common areas of difficulty might be …….

  10. Common Areas of Difficulty: • not attempting all questions • using an incorrect number of significant figures in their answers • not using the information provided • not using correct conventions to draw molecules in three dimensions • not using the correct rules to draw Lewis structures and using the wrong number of electrons

  11. not using correct conventions to draw molecules in three dimensions • not using the correct rules to draw Lewis structures and using the wrong number of electrons • not differentiating between chemical and physical properties (e.g. described low melting/boiling points being due to an element being unreactive) • not writing their responses in a clear and concise fashion.

  12. Skills Chemical Literacy Planning Well documented/set out calculations Problem Solving

  13. Chemical Literacy Understanding in chemistry is determined when we address chemical phenomena in the three dimensions by which they are demonstrated

  14. Turn to your neighbor and discuss this diagram. What is meant by each of the dimensions? Give of an example of each.

  15. Observations (macro) • what can be seen, touched, smelt • chemical & physical properties • chemical reactions • physical changes • quantitative measures • Particles (submicro) • models used by chemists • nature of particles present: atoms, molecules, ions • interactions between particles • changes to particles/numbers of particles • Symbols • symbols • formulae • equations • calculations • graphs

  16. NaCl(s) → Na+(aq) + Cl-(aq) Example: salt dissolving Polar water molecules are attracted to the positive and negative ions surrounding them, reducing the attractive forces between them so they begin to move freely and no longer hold fixed positions relative to each other.

  17. Try this one The following table provides information about 0.100 mol L-1 solutions of ammonia, ammonium nitrate and nitric acid. Account for the variation in properties. So chemical literacy is demonstrated through explanations that accurately link observations to the nature of the particles involved and represent these using chemical equations.

  18. Interpretation of observations

  19. Symbolic representation

  20. Particles present

  21. Saying Enough The Right Way • Take care when using “chemistry” terms that you show you know what they mean • van der Waals forces • electronegativity • effective nuclear charge

  22. Planning Answers • scaffolding an explanation to provide a logical analysis of the material and to show the constituent parts of an explanation • discuss reasons for the differences in the polarities of BF3 and PF3 • graphic organiser for comparisons Example eg. Starting point

  23. BF3 PF3 Shape of electron pairs around central atom No. of electron pairs around central atom Tetrahedral 3 electron pairs Trigonal planar 4 electron pairs Similarities • Both have a central atom surrounded by three F atoms. • The position of B and P in the Periodic Table indicate that they would have similar electronegativities. • B—F and P—F bond polarities would be similar. Differences

  24. Balanced / unbalanced shape Polarityofmolecule Trigonal planar Balanced; bond dipoles cancel Shape of molecule Trigonal pyramidal Unbalanced; bond dipoles add to give a net overall dipole Polarmolecule Non-polarmolecule Summary BF3 is non-polar. B and F have different electronegativities so the B–F bond is polar covalent. The shape of the molecule (trigonal pyramid) is symmetrical about the central B atom, so bond dipoles cancel / add to zero to give no net dipole or symmetric distribution of charge about the central atom. PF3 is polar. P and F have different electronegativities so the P–F bond is polar covalent. The shape of the molecule (trigonal pyramid) so the molecule is asymmetrical about the central P atom, so the P–F bond dipoles add to give a net dipole or there is an asymmetric distribution of charge about the central atom.

  25. Try this one Explain why water has a higher boiling point than hydrogen sulfide, H2S.

  26. H2O H2S Similarities • Both involve two H atoms bonded to a central non-metallic atom • Same shape • Both molecular substances • Both polar molecules due to bond polarity and shape Differences Weak attractive forces exist between water molecules Weak attractive forces are slightly larger due to the greater number of electrons in the S atom compared with the O atom. Temporary and induced dipoles

  27. Hydrogen bonding O –H bonds very polar because of large electro negativity difference. This leads to hydrogen bonding. S –H bonds moderately polar because of moderate electro negativity difference. No hydrogen bonding. Summary Water and hydrogen sulfide are molecular substances. Weak attractive forces due to temporary and induced dipoles exist between both water and hydrogen sulfide molecules, however the attractive forces between hydrogen sulfide molecules due to these attractive forces are slightly larger due to the greater number of electrons in the sulfur atom compared with the oxygen atom. Because of the electro negativity differences between O and H atoms and between S and H atoms, both water and hydrogen sulfide molecules have polar covalent bonds, which combined with the unbalanced shape of each molecule, makes them polar molecules. Both molecules have dipole – dipole intermolecular attractive forces, however, the extreme differences in electro negativity between H and O atoms leads to relatively strong attractive forces called hydrogen bonding existing between water molecules and not between hydrogen sulfide molecules. This leads to water molecules having overall much stronger intermolecular forces of attraction than hydrogen sulfide molecules and therefore much higher boiling points.

  28. Problem-Solving Hints for Chemical Calculations Some general steps:

  29. Remember • chemistry is much more than just solving mathematic puzzles or ‘plugging numbers into a calculator”. • whenever you solve a numerical problem think about what the numbers actually represent on the molecular level i.e. in terms of atoms and molecules

  30. Assessment Of Practical Skills Knowledge of experimental procedures:

  31. Understanding Practical Work • Method for titration analysis of ethanol (2004) • Method for preparation of ester (2005) • Method for iodometric titration (2006) • Back titration (2007) • Method for chloride analysis (2008) • Method for preparation of ester (2009)

  32. Sources of Practice Questions • 2004 – 2009 NZQA Scholarship Papers • NZIC Scholarship Examinations • AME Scholarship Chemistry (Giffney) • Bestchoicewww.bestchoice.che.auckland.ac.nz • NZEST Papers www.nzest.ac.nz/resources.html • Old Scholarship Papers (Check at school) • 1st year University Texts Note: Last 3 resources may provide appropriate ‘level’ of questions. However, the style of the questions may not mirror those in the Scholarship examination

  33. What Can You Do To Prepare Yourself

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