What Does It Take to Score an A in Combined Chemistry?

Key Takeaways

• Getting an A in Combined Chemistry requires more than memorising definitions and formulae. You also need to apply concepts, explain your reasoning clearly and work accurately under exam conditions.
• Strengthen your understanding of key areas such as mole calculations, acids and bases, chemical bonding, metals and rates of reaction.
• Focus on the reasoning behind common reactions and observations, so you can handle unfamiliar question contexts with greater confidence.
• Use a clear method for calculations, build a bank of scientific keywords and review mistakes carefully to avoid losing marks unnecessarily.
• Structured guidance and targeted practice at Mr Khemistry can help close knowledge gaps, improve your exam technique, and help you feel more prepared for the O-Level exams.

Introduction

You may have revised a chapter, completed the school worksheet and even memorised the key definitions, only to open up the Chemistry component of your O-Level Combined Science paper and get stuck. Perhaps the question looks different from the examples you practised, or maybe it asks you to explain an observation using words you cannot quite recall. These are the moments when Combined Science (also known as G2 Science) can feel more challenging than expected.

The encouraging part is that struggling with these questions does not mean you are “bad” at Chemistry. It usually means there are a few gaps in how you approach the subject, whether that is applying concepts, writing explanations or checking your working carefully.

Below, we look at what it really takes to work towards getting an A in Combined Chemistry, along with practical ways to revise more effectively and avoid losing marks unnecessarily.

What Do You Need to Get an A in Combined Chemistry?

Scoring well in Combined Chemistry is not just about recognising a topic. You need to understand the concept, apply it correctly and present your answer clearly to secure the mark.

O-Level Chemistry questions often test several skills at once. Even if you know the topic, you can still lose marks through incomplete explanations, inaccurate answering techniques, unclear working or small mistakes like wrong units or unbalanced equations.

Key skills include:

• Understanding core topics, such as mole calculations, acids and bases, chemical bonding, metals and the reactivity series, energy changes and rates of reaction
• Applying concepts to unfamiliar questions rather than relying on memorised answers
• Explaining observations clearly using appropriate scientific keywords
• Showing clear and logical working in calculations
• Checking details carefully, including units, formulae and balanced equations

These skills are what allow you to turn Chemistry knowledge into marks on the page, and they usually need to be built through steady, focused practice rather than last-minute memorisation.

1. Learn the “Why” Behind Common Chemistry Explanations

Combined Chemistry questions often ask you to explain an observation, rather than simply state what happens. This is common in topics such as rates of reaction, bonding, and acids and bases.

For example, do not only memorise that a higher temperature increases the rate of reaction. Understand that particles gain more kinetic energy, move faster and collide more frequently. A greater proportion of these collisions also have sufficient energy for a reaction to occur.

This matters when the question changes the context. You may be shown a different experiment involving marble chips and acid, or given a graph of gas produced over time, but the explanation still comes back to collision theory.

2. Focus on Reaction Patterns You Can Apply

In Combined Chemistry, you are often expected to predict what happens when substances react, especially in questions on acids, metals and the reactivity series. The key is to understand the pattern behind the reaction rather than memorising individual examples.

Take metals and dilute acids. Metals above hydrogen in the reactivity series, such as magnesium and zinc, react with dilute hydrochloric acid to form a salt and hydrogen gas. Metals below hydrogen, such as copper, do not react with dilute hydrochloric acid in the same way.

This helps when you are given an unfamiliar metal in an exam question. Rather than relying on memory alone, you can use its position in the reactivity series to predict whether a reaction is likely to occur and how vigorous it may be.

3. Treat Mole Calculations as a Process, Not a Shortcut

Mole calculations are a common area where students lose marks in Combined Chemistry, particularly when questions involve mass, concentration, gas volumes, or reaction ratios. The calculation may look straightforward, but one missed conversion or incorrect ratio can affect every later step.

Use the same routine each time:

1. Identify what the question gives you and what it is asking for.
2. Convert units where needed, especially cm³ to dm³ in concentration questions.
3. Write the relevant formula.
4. Balance the chemical equation before using the mole ratio.
5. Show each calculation step clearly.
6. Include the correct unit in your final answer.
7. Check whether the answer is reasonable.

For example, when calculating the concentration of a solution, it is easy to substitute a volume in cm³ directly into a formula that requires dm³. Writing the conversion first can prevent this avoidable error.

4. Build Topic-Specific Keyword Banks

Structured questions in Combined Chemistry often award marks for the scientific reason, not just the final observation. A keyword bank can help you recall the language needed for common topics.

For chemical bonding, you may need phrases such as “strong electrostatic forces of attraction” or “free-moving electrons”, depending on the substance and property being explained. This shows that you understand both the observation and the Chemistry behind it.

5. Review Errors by Topic and Question Type

When you mark a worksheet or practice paper, avoid treating every wrong answer in the same way. In Combined Chemistry, the cause of an error often points to the area you need to revise.

For example, you may have:

• Used the wrong mole ratio because the chemical equation was not balanced
• Lost a mark because you stated an observation without giving a scientific reason
• Made a concentration error by forgetting to convert cm³ to dm³
• Misread a practical question and described the result instead of explaining the trend
• Named the wrong metal reaction because you were unsure how to use the reactivity series

Keep a simple mistake log with headings such as “Mole Calculations”, “Acids and Bases” and “Explanation Questions”. Before starting your next revision session, revisit a few mistakes from the same topic and complete one or two similar questions. This makes your revision more targeted and helps prevent the same gaps from appearing again in the exam.

How Mr Khemistry Helps You Build Stronger Chemistry Skills

The Chemistry revision strategies above can make a real difference, but they are not always easy to build on your own. You may know that you should review mistakes, practise more application questions or revisit weaker topics, yet still feel unsure about where to begin or whether you are using the right method.

This is where structured guidance can help. At Mr Khemistry, our Combined Chemistry tuition classes provide expert guidance to help students work through common challenges and make steady progress in the subject.

Break Down Difficult Topics More Clearly

Some topics, such as mole calculations and chemical bonding, can feel confusing when several ideas are introduced at once. Our Chemistry tutors will use bite-sized explanations, visuals, analogies and worked examples to help you see how each step connects.

Instead of being given a completed mole calculation to memorise, you will be guided through how to identify the information given, select the right formula, use the balanced equation and check whether your final answer makes sense.

Practise the Skills That Often Cost You Marks

Understanding a topic is important, but you also need to know how to answer exam questions clearly. Through summary notes, topical drills, worksheets, quizzes and short assessments, you can practise the question types that often cause students to lose marks.

This may include explaining experimental observations using the right keywords, setting out calculation steps logically or applying a familiar concept to an unfamiliar scenario. The aim is to help you recognise what each question is testing and respond more confidently.

Receive Support Before Small Gaps Become Bigger Problems

With weekly onsite or online lessons, smaller class settings, access to the student portal and 24/7 WhatsApp support for questions, you have more opportunities to clarify doubts as they arise. This can be especially helpful when you are revising independently and get stuck on a question after class.

Over time, this more structured approach can help you build stronger habits, close knowledge gaps, and feel more confident in achieving an A in your Chemistry exam.

Conclusion

Working towards an A in Combined Chemistry isn’t about trying to memorise every possible concept and answer before you walk into the exam hall. Rather, it’s about building the habits that help you make sense of a question, choose the right approach and present your answer with care.

When you need more structured support, Mr Khemistry, a reliable and accessible Chemistry tuition centre in Singapore, is here to help. Our Combined Chemistry classes are designed for students who are tired of looking at a question and not knowing how to begin. With our expert guidance, you can learn how to break down unfamiliar questions, spot the concepts being tested and work towards an answer with greater independence.

Get in touch with us today.

Frequently Asked Questions

How many past-year papers should I complete before the O-Level Combined Science exam?

There is no fixed number, but aim to complete enough papers to become familiar with the usual question types, timing and mark allocation. Start with topical questions while you are still strengthening individual chapters, then move on to full papers as the exam approaches. The most important part is reviewing each paper carefully, especially the questions where you lost marks.

What should I do if I keep getting calculation questions wrong?

Do not just redo the same question immediately. First, identify where the mistake happened. You may have used the wrong formula, missed a unit conversion, copied a value incorrectly or used the wrong mole ratio from the balanced equation.

Once you know the cause, practise a few similar questions using a fixed step-by-step method. Write down the given data, convert units, state the formula, show your working, and check whether the answer is reasonable. This makes your approach more consistent under exam pressure.

Is it better to revise Combined Chemistry by chapter or by question type?

Both are useful at different stages. When you are still learning a topic, revise by chapter to strengthen the concepts. As the exam approaches, include revision by question type too, such as mole calculations, structured explanations or practical-based questions. This helps you recognise recurring answering techniques, even when the topic or scenario in the question changes.