Public Assessment of the HKDSE Chemistry Examination 1. Public Assessment The public assessment of the Hong Kong Diploma of Secondary Education (HKDSE) Chemistry Exam consists of a public examination component and a school-based assessment component. A. Public Examination component In Chemistry, the mark of the public examination component contributes 80% of the final subject mark. Paper Section Question types Weighing Duration Curriculum Paper 1 Section A Multiple-choice Questions 18% 2 hours 30 minutes Compulsory Part Section B Short Questions and Structured / Essay-type Questions 42% Paper 2 – Structured Questions 20% 1 hour Elective Part (2 out of 3) B. School-based Assessment component In Chemistry, students are assessed by their teachers on their performance of a wide range of skills involved in practical and non-practical related tasks throughout S.5 and S.6. The mark of the school-based assessment component contributes 20% of the final subject mark. Year of examination Assessment types Weighing 2012 and 2013 Practical related component 20% Starting from 2014 Practical related component 16% Non-practical related component 4% 2. Standards-referenced Reporting The HKDSE makes use of standards-referenced reporting, which means candidates’ levels of performance will be reported with reference to a set of standards as defined by cut scores on the variable or scale for a given subject. The following diagram represents the set of standards for a given subject: Cut scores U 1 2 3 4 5 Variable/ scale Within the context of the HKDSE there will be five cut scores, which will be used to distinguish five levels of performance (1–5), with 5 being the highest. The Level 5 candidates with the best performance will have their results annotated with the symbols ∗∗ and the next top group with the symbol ∗. A performance below the threshold cut score for Level 1 will be labelled as ‘Unclassified’ (U). I
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Public Assessment of the HKDSE Chemistry Examination1. Public AssessmentThe public assessment of the Hong Kong Diploma of Secondary Education (HKDSE) Chemistry Exam consists of a public examination component and a school-based assessment component.
A. Public Examination componentIn Chemistry, the mark of the public examination component contributes 80% of the final subject mark.
Paper Section Question types Weighing Duration Curriculum
Paper 1Section A Multiple-choice Questions 18%
2 hours 30 minutes Compulsory Part
Section B Short Questions and Structured / Essay-type Questions 42%
Paper 2 – Structured Questions 20% 1 hour Elective Part (2 out of 3)
B. School-based Assessment componentIn Chemistry, students are assessed by their teachers on their performance of a wide range of skills involved in practical and non-practical related tasks throughout S.5 and S.6. The mark of the school-based assessment component contributes 20% of the final subject mark.
Year of examination Assessment types Weighing2012 and 2013 Practical related component 20%
Starting from 2014Practical related component 16%
Non-practical related component 4%
2. Standards-referenced ReportingThe HKDSE makes use of standards-referenced reporting, which means candidates’ levels of performance will be reported with reference to a set of standards as defined by cut scores on the variable or scale for a given subject. The following diagram represents the set of standards for a given subject:
Cut scores
U 1 2 3 4 5
Variable/scale
Within the context of the HKDSE there will be five cut scores, which will be used to distinguish five levels of performance (1–5), with 5 being the highest. The Level 5 candidates with the best performance will have their results annotated with the symbols ∗∗ and the next top group with the symbol ∗. A performance below the threshold cut score for Level 1 will be labelled as ‘Unclassified’ (U).
I
Exam StrategiesSection A Multiple-choice Questions
1. The statements in the options may be misleading. Do not spend time in reading the 4 options only.
To tackle the problem, follow the steps below:• Read the question (not options) twice or more.• Recall the related situation / knowledge.• Organize the memory.• Read the options. Cross-out the incorrect options if necessary.• Choose the correct answer.
Example:
Which of the following methods is used to test for oxygen?
A. Bubbling the sample gas into limewater.
B. Putting a glowing splint into a gas jar containing the sample gas.
C. Bubbling the sample gas into barium chloride solution.
D. Putting a burning splint into a gas jar containing the sample gas.
Ans: B
2. The given statements may be correct. However, each of them may or may not be a relevant explanation to the situation.
To tackle this kind of question, think critically about the relationship between the situation and each of the options.
Example:
Aluminium can be used to manufacture overhead power cables because it is
(1) cheap.
(2) corrosion resistant
(3) Non-poisonous
A. (1) only
B. (3) only
C. (1) and (2) only
D. (1), (2) and (3)
Ans: C
II
Fossil Fuels and Carbon Compounds
55 Fossil Fuels and Carbon Compounds
Fossil Fuels and Carbon Compounds
Fossil Fuels Homologous Series Burning Fuels Consequences of Using Fossil Fuels
Direction of electron flow in the external circuit
Voltage recorded
Mg MgtoCu +1.42V
Zn ZntoCu +1.10V
Pb PbtoCu +0.46V
Ag CutoAg -0.17V
Table 8.2
Vmagnesium
copper
filter papermoistened withsodium chloridesolution
+−+1.42V
electron flow
Vsilver
copper
+−−0.17 V
electron flow
Figure 8.9
D
165
Chemical Cells
HKEP
Lithium ion battery
Alithiumionbattery is fromthefamilyofrechargeablebatterytypes. In the battery, lithium ions move from the negativeelectrode (anode) to thepositive electrode (cathode) throughthenon-aqueous electrolyte and separatordiaphragmduringdischarging,andfromthecathodetotheanodeduringcharging.Dependingon thekindsofmaterials a lithium ionbattery ismadeupof,thevoltage,capacity,lifeandsafetyofthebatterycanchangedramatically.
Lithium ionbatteries are one of themost popular types ofrechargeable batteries common used in different kinds ofconsumerelectronics. It isbecause theyhavehighenergydensities,nomemoryeffect,andaslow lossofchargewhennotinuse.Lithiumionbatteriesarealsogrowinginpopularityformilitary,electricvehicleandaerospaceapplications.
Section A Multiple-choice QuestionsHint 1 Thechoiceofelectrodesshouldbeconsidered.
Hint 2 Asaltoftheelectroplatingmaterialisusedastheelectrolyteforelectroplating.
Hint 3 Considerthenatureoftheelectrodes.
Hint 4 Recalltheexperimentalset-upforthepurificationofcopper.
Hint 5 Whatchargedoescationcarry?
Section B Short Questions and Structured / Essay-type Questions
Hint 6 Issugaranelectrolyte?
Hint 7 Don’tgivethechemicalformulaonly.Thenameofthechemicalisrequiredhere.
Hint 8 Thenatureoftheelectrodesisafactorwhichaffectsthepreferentialdischargeofions.
Hint 9 Ioniccompoundshavemobileionswhentheyareinmoltenoraqueousstates.
Hint 10 Acidicandalkalinesolutionsturnlitmussolutiontoredandbluerespectively.
Hint 11 DoNOTgiveformulaeastheanswers.
Hint 12 Seawatercontainsmobileions.
Hint 13 Stateclearlythe+veand-vepoleofthea.c.supply,andgivethecontrolexperiment.
Hint 14 IfnoFe2+ionisformed,norustingwilloccur.
Hint 15 Considerthechangeofoxidationnumbers.
Hint 16 Payattentiontothereactivityoftheimpuritiescomparedtocopper.
Hint 17 Recall‘RedCat’.
Hint 18 Studentsshouldanswer‘true’or‘false’first.TheformulaofXNO3(aq)providestheinformationaboutthechangeintheXn+ion.
Hint 19 ThecolourofCuSO4(aq)solutionisblue.
Hint 20 Thisisanessay-typequestion,sopointformisNOTacceptable.
248
Chemistry: Key Notes & Exambuilder
RateofReaction4.8
This section is written in accordance with the HKDSE Combined Science (Chemistry) Examination Syllabus. Students studying the HKDSE Chemistry Examination Syllabus should skip this section and study Chapter 11 in Book 3.
• Average rateistheaveragereactionratemeasuredoveraperiodoftime.
A
• D[ ] means change of
concentration.
• The rate of reaction is
inversely proportional to
the length of time, i.e.,
rate ∝ 1
time.
• Rate of react ion is a
pos i t i ve quant i ta t i ve
e x p r e s s i o n . S o a
negat ive s ign should
be given to the change
of concentration of the
reactant.
285
Question Commands
Question CommandsQuestion command(s) Example(s)
What / Which ...
(Simple answer is usually required.)
What gas evolves?
Correct answer: Sulphur dioxide / SO2
What is the direction of electron flow in the external circuit?
Correct answer: From left to right
Which of the following compounds can be used to make an addition polymer?
H
C HC = C H2N NH2 OH
Correct answer: H
C HC = C
Suggest a formula ... The oxide of aluminium is insoluble in water, suggest the formula for this oxide.Correct answer: Al2O3
Incorrect answer: Aluminium oxideName ...
(Formula / Structure is NOT accepted.)
Name an element which is a metalloid.Correct answer: BoronIncorrect answer: B
Write the chemical equation ...
(Al though both chemical equation and ionic equation a r e a c c e p t e d , t h e b e s t answer should be a chemical equation.)
Write a chemical equation for the reaction when adding dilute hydrochloric acid to zinc granules.Correct answer: Zn + 2HCl → ZnCl2 + H2 (chemical equation)Poor answer: Zn + 2H+ → Zn2+ + H2 (ionic equation)
Write the chemical equation ... Write a chemical equation for the reaction between sodium and water. State symbols should be given.Correct answer: 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g) (Score 2 marks)Poor answer: 2Na + 2H2O → 2NaOH + H2 (Score 1 mark only) (Remarks: 1 mark for equation and 1 mark for state symbols)
Write an ionic equation ... Write an ionic equation for the reaction when adding hydrochloric acid to sodium carbonate.Correct answer: 2H+ + CO3