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The Top 5 Tips To Max Out Your Chemistry Trial Marks

In this article, Head Chemistry Teacher Michelle Wong gives her top 5 tips to help you ace your HSC trials.

You may have spent hours memorising the dot points for your HSC Chemistry exam and practising mole calculations… but how’s your exam technique? Lots of students know the content back to front and inside out, but they still manage to lose marks because they haven’t done what the markers want. Don’t be that guy! Here are the top 5 tips to make sure you max out your Chemistry Trial marks.

 

1. Analyse the Question Carefully

Chemistry isn’t English, but Chemistry exam questions can still be a few sentences long. It’s really easy to miss an important word or forget to mention something important, especially when you’re writing a long response.

What to do:

Underline all the keywords in the question. Put a box around the keyword. When you’ve finished writing your response, check that you’ve addressed each underlined word.

At the end of the exam, if you have time left over, go back and check that you’ve addressed all the parts for each question.

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Excerpt From The Matrix Chemistry Trial Exam Prep Course

 

Common things that students miss:

  • “Assess” and “evaluate”: make sure you’ve included an assessment or evaluation in your answer. You will almost always lose a mark if you haven’t included one in your response. Write the word “assessment” or “evaluation” in your answer clearly so the marker can award you the mark easily.
  • “Provide examples”, “include equations”: give at least two examples or equations.
  • Multi-part questions (e.g. with two keywords): make sure you don’t forget to answer part of the question.
  • “Explain” means you need to answer with reference to scientific principles and relate them, not just describe what’s happening.

 

2. Plan Your Long Responses Before Writing Them

Long responses can be hard to write, especially if you picked Chemistry because you thought you could avoid writing essays! It’s important to plan your answers before writing them, for several reasons:

  1. Planning your answers at the beginning of the exam gives you more time to remember things you missed, or pick up ideas for what to include from other questions in the exam
  2. If you did miss something, you can insert it in your plan rather than try to find room in the answer space to squeeze it in
  3. It’s much easier to check that your summarised plan addresses the question, rather than trying to see if your multi-page answer addresses it
  4. Often for longer 6-7 mark responses, you need to “provide a coherent and concise response with no irrelevant, extraneous information” to get full marks – that means no waffling, or padding your answer out with unrelated information and hoping you get marks for it!

Plans for long responses should be quite comprehensive – three-word plans won’t be very useful for a 6-7 mark question.

 

What to do:

At the beginning of the writing time, go through and analyse the questions in the paper. For any questions that are 4 or more marks, construct a detailed dot point plan. Then start writing your answers.

 

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Excerpt From Student’s Matrix Chemistry Trial Workbook

 

3. Don’t Round Off Too Early In Calculations

The rule for rounding in calculations is that your answer should be given to the least number of significant figures used in your calculation. But that doesn’t mean that you can round off your working!

Rounding a number makes it less accurate.

If you round off a number, then perform more mathematical operations on it, your answer will get less and less accurate.

Take this mole calculation, for example:

25.0 mL of 0.353 M hydrochloric acid required 21.4 mL of sodium hydroxide solution to neutralise. What was the concentration of the sodium hydroxide?

HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(aq)

Without rounding

With rounding

n(HCl) = 0.353 x 0.025 = 8.825 x 10-3 mol

n(NaOH) = 8.825 x 10-3 mol

c(NaOH) = (8.825 x 10-3) / 0.0214 = 0.412 M (3 s.f.)

n(HCl) = 0.353 x 0.025 = 8.825 x 10-3 mol = 8.83 x 10-3 mol (3 s.f.)

n(NaOH) = 8.83 x 10-3 mol (3 sig fig)

c(NaOH) = (8.83 x 10-3) / 0.0214 = 0.413 M (3 s.f.)

This is particularly important in pH calculations, where taking the log10 of a rounded number can make your answer very different!

What to do:

Include 2 – 3 more digits in the intermediate calculation steps than you’ll eventually need in your final answer. You can also use your calculator’s storage functions to keep the unrounded numbers, but it’s a good idea to write down the unrounded numbers every once in a while in your working so it’s easier to check your working later.

 

4. Include Subscripts In Chemical Equations

Some schools will deduct a whole mark if you leave out a single subscript in your balanced chemical equation! It feels really unfair, but in some situations, it’s very important – you can stand safely next to a large beaker of aqueous HCl, but you don’t want to inhale a large quantity of HCl(g)!

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Don’t toss away your marks!

 

Take note of hints in the question about what state the substance is in:

  • “Solution” = aqueous
  • “0.1 M” = aqueous or gas
  • “Vapour” or “bubbles” = gas
  • “Powder” “pellets” “precipitate” = solid

In general, the states you’ll give in equations for the HSC are for the substances at 25 °C and 100 kPa.

If you can’t work out a particular state, think back to the properties of substances at room temperature that you learned in Year 11. For example, ionic compounds tend to have high melting points, so they are almost always solid or aqueous at room temperature. There are only 2 liquid elements at room temperature and 11 gases (can you remember them?).

What to do:

Make a habit of writing the relevant subscript immediately after you write each term in the chemical equation. You might think that you’ll go back and add subscripts later… but it’s very easy to forget.

 

5. Revise General Chemistry Skills

Chemistry skills aren’t clearly in the module dot points, but there are always a substantial number of questions in Chemistry exams that test your ability to “science well”.

Make sure you’re familiar with:

  • How to draw graphs – (Which axis goes where? What scale should you use? What symbols do you use? Do you draw a straight or curved line of best fit? How do you label your axes? How do you show working? How do you show regions where you’ve extrapolated?)
  • How to draw diagrams – (How do you label? Are your diagrams large enough? Neat enough? When do you use arrows? How much detail do you need?)
  • How to talk about first-hand investigations – (What do validity, reliability and accuracy mean? How do you improve these for each specific investigation? What safety protocols are appropriate? What are the expected results? What do you need to include in a procedure? Which variables need to be controlled? What are the sources of error?)

 

Want to Take Your Chemistry to the Next Level?

The HSC Exams are almost here! Are you ready?

Matrix HSC Prep Courses cover all the subjects and syllabus dot-points you need to help you maximise your trial marks. Learn how to get HSC Exam ready in 6 days!

 

Written by Michelle Wong

Michelle is the Senior Chemistry Teacher at Matrix Education, and has been tutoring Chemistry and Mathematics for over 15 years.

 

© Matrix Education and www.matrix.edu.au, 2018. Unauthorised use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Matrix Education and www.matrix.edu.au with appropriate and specific direction to the original content.

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