This year’s DSE Chemistry paper required caution, and a grasp of experiment-based questions, say secondary school teachers and commercial tutors.
Beacon College tutor Wong Kwan-ho, who goes by K. C. Daniel, who sat the exam himself, said this year’s Paper 1 (which consists of 36 multiple choice questions in section A and 14 long questions in Section B) was one of the hardest he’s seen.
In the multiple choice section, a neglect of minor details could cause the student to pick the wrong answer. For example, in Q. 3, students needed to look at the periodic table to decide whether one of the statements was true. Since the rows weren’t numbered, students might easily forget that the first row is the one that only contains hydrogen and helium. Also, if students missed the keyword “recharge” in Q. 15, they mistakenly have thought that electrons must be flowing from the negative electrode and pick the wrong answer.
Question 29 was another tricky question, where students who did not draw and count the hydrogen atoms when sketching the compound may have overlooked a double bond. “Even when I was re-checking my paper I found several subtle traps,” Wong said. “Many students tell me the paper seems very easy, but I don’t think so.”
Another tutor, K. Kwong from Modern Education, also said the key to tackling some of the trickier questions, which included Q. 11, 20, 24, 29 and 31, was simply being careful. He added that Q. 11 had been set to waste students’ time. Some would calculate the oxidation number for each of the answer options, but smart students should be able to see right away that the answer was A because that compound had three fluorine atoms.
Cheung, a secondary school teacher, said he noticed an obvious focus on redox questions in the multiple choice paper.
Several questions tested students’ knowledge of acids and bases. Wong said this was because last year’s exam report found students were weak in this area. He said it was a good idea for future candidates to ask teachers and markers’ advice to see which topics students didn’t do well on the previous year, so they can spend more time tackling them. Cheung said it was common for multiple choice questions that students scored badly on one year to be turned into a long question the following year.
In Section B, Cheung said he was surprised to see two questions involving terminology, such as Q. 10, which asked students the meaning of dynamic equilibrium. The other was Q. 7, which tested an understanding of the difference between “heat change” and “enthalpy change”.
“Some of these involved quite challenging concepts that are rarely tested, so teachers may not have gone into it too deeply in class, or drilled their students on it,” he said.
More than 10 marks were allocated to explaining certain phenomenon, such as Q. 4 (c), which asked students to suggest why at room temperature and pressure, CO2 is a gas but CS2 is a liquid. “You really have to get the right keywords in order to score. It’s only a 2-mark question, but I think many students may have written everything they could think of, and not only miss the point, but waste a lot of time while doing so,” said Wong. “So it’s important to know your concepts and the related keywords.
“Some students only focus on revising equations, graphs, or multiple choice questions. But that does not train you for this type of question.”
One student who took the chemistry exam today said the paper wasn’t too hard, but she didn’t have enough time to check her answers. “I had to guess some of the multiple choice questions because some were very ambiguous.”
Poon, a secondary school teacher, said he noticed that more than 50 per cent of the marks focused on four main topics: acid/base, metals, electrolysis and fossil fuels.
Paper 2, where students pick two out of three sections to answer, was easier compared to earlier years, said Poon. He said many of the questions could be answered if students had memorised some basic concepts. A teacher in a Band 2 school, he said many of his students focused on tackling the relatively easier Analytical Chemistry section. But this question was one of the harder ones this year, involving an unfamiliar topic of calibration curve.
He also noticed a trend towards asking students more about experiment procedures, requiring students to know why experiments are designed in a certain way, and the concepts behind them. “It’s great if students can spend more time in the lab to tackle these questions, but the syllabus is so tight we can’t devote too much of the lesson to conducting experiments, even though the examination authority keeps emphasising this,” he said. “They’d need to cut 10 to 20 per cent of the syllabus for us to do that. Right now, even some of our school-based assessments have to be conducted outside of class.”
Another teacher, surnamed Lee, agreed that the DSE curriculum offered little room for lab time. The best way to cope, he said, was to watch YouTube videos of experiments mentioned in textbooks.
Lee recommended doing test questions immediately after a certain topic is taught at school, instead of waiting until exam time. Melody Tam, a top scorer from last year’s DSE who got Level 5** in chemistry, said she start drilling various topics beginning in Form Four, and completed 20 years of HKCEE papers by the time she sat the exam.
“In Form Six, I started doing A-Level papers for selected topics such as enthalpy and organic chemistry,” she said. “It’s best to ask teachers to select suitable questions for you to do, because many aren’t on the DSE syllabus.”
Wong, a student who sat the exam, said she felt well prepared because she did a lot of mock papers from different schools. “Some good mock papers set some difficult questions to make you think more; others also make the difficulty level and length of the questions very similar to the real exam so you can practise time-management,” she said.
“I certainly had fun today. I enjoy the twists and finding answers to new questions using knowledge I revised.”