This year’s DSE Chemistry exam offered fairly standard, straightforward questions with no unexpected surprises. While slightly easier than last year, both papers nevertheless expected students to have in-depth knowledge of the syllabus, students and teachers said.
Kwok Wing-yan, 17, from True Light Girls’ College, said the exam was not too difficult. The short questions in Paper One and Two provided enough clues for candidates to answer correctly, she said, while the multiple choice questions required students to have a “thorough understanding of each topic”.
Wing-yan said the most difficult question was Q9 from Section B of Paper One. The short essay question asked candidates to deduce, and illustrate, how tetraflouroethene (CF2=CF2) undergoes polymerisation to form Teflon.
“As tetraflouroethene is not [an example] in the textbook, it took me some time to decide whether it was addition polymerisation or condensation polymerisation … I didn’t know what to include [in the answer].”
To earn full marks, King’s Glory Educational Centre’s tutor Samuel Chong said candidates needed to be able to answer the question with particular phrases exactly.
“They had to mention that addition polymerisation is a process without the elimination of small molecules, that it requires one type of monomer which is an unsaturated molecule, and that it contains a Carbon-Carbon double bond,” he said.
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Chong said that in recent years, an increasing amount of questions have been designed to test a student’s ability to explain how a chemical process works, or its underlying principles.
“Most students know how to do calculations or write equations, but they don’t spend enough time on revising chemical theories,” he explained.
Byran Tse, a 17-year-old student from Wah Yan College Kowloon, said he also found Section A of Paper One to be relatively challenging. He said something he did not expect was the last essay question in Section B of Paper One, which asked students to explain the acid-base properties of three different oxides found in the second period of the periodic table.
Byran said the question was hard, because it wanted students to list out proper formulas to illustrate their answers.
Modern Education’s tutor Sam Chai said questions on iodometric titration had reappeared, and that this was a concept that had not appeared on the paper since 2007.
This question, Q3b of Section C in Paper Two, required specific calculation methodologies, he said, but added that students who have revised similar questions should have been able to complete it without too many difficulties.
Chong advised students taking the exam next year to practise questions that “fuse chemical theories with daily-life examples”. This is a question type that has cropped up quite frequently in recent years. He also emphasised that students should make sure the wording they used in their answers are as accurate as possible.