CER Framework: How To Answer Open-Ended Science Questions

PSLE science can feel intimidating at first. Long questions, unfamiliar phrasing, and answers that do not seem to match what you memorised can make the paper look harder than it really is. Many students walk out thinking, “I knew this, but I still lost marks.” That frustration usually comes from not understanding how answers are marked, rather than from a lack of ability.

Once you realise that science is more about understanding ideas than spotting fancy words, things start to click. When the concepts are clear in your mind, open-ended questions become far less scary. Instead of guessing what the marker wants, you learn how to explain your thinking in a way that earns marks naturally.

Why open-ended science questions feel tricky

Unlike multiple-choice questions, open-ended science questions do not give hints. You must explain what you know clearly, step by step. Many students think that success depends on memorising keywords from the textbook, so they panic when they cannot recall the “exact wording”.

Markers are not looking for robotic answers. They want to see whether you understand what is happening in a scientific situation. If your answer shows clear thinking and accurate science, you can still score well even if your wording is slightly different from the model answer.

This is where the CER Framework becomes useful.

What is the CER Framework?

CER stands for Claim, Evidence, and Reasoning. It is a simple structure that helps you organise your thoughts when answering open-ended science questions.

Instead of writing random sentences and hoping something sticks, CER gives your answer a clear flow. It helps you focus on concepts first, then support them properly.

Here’s how it works:

1. Claim: Start by answering the question directly

The Claim is your main answer. It should respond directly to what the question is asking.

If the question asks, “Which material is the best insulator?” your claim might be: “The plastic cup is the best insulator.”

This shows the marker immediately that you understand the question and are confident about your answer. Many students lose marks simply because their first sentence is vague or avoids giving a clear answer.

2. Evidence: Support your claim with observations or facts 

The Evidence is where you use information from the question, diagram, or experiment. This could include observations, results, or data.

For example: “The temperature of the water in the plastic cup decreased the least over 10 minutes.”

Evidence proves that your claim is not a guess. It shows that you are using the given information correctly, which is something markers reward.

3. Reasoning: Explain the science behind it

The Reasoning is the most important part, and also the part students struggle with most. This is where concepts matter more than keywords.

You explain why your evidence supports your claim using scientific ideas: “Plastic is a poor conductor of heat, so less heat is lost to the surroundings.”

Even if you forget a specific term, explaining the idea clearly can still earn you marks. This is why understanding concepts beats memorising phrases every time.

Keywords vs concepts: What markers really look for

There is a common myth that missing one keyword means losing all the marks. In reality, markers award marks based on whether the key idea is present.

For example, you might forget the word “evaporation” but explain that “water changes into water vapour and escapes into the air”. That still shows understanding. Marks are awarded for meaning, not just vocabulary.

That said, learning keywords is still useful. Keywords help you be precise and save time. The problem comes when students memorise words without knowing what they actually mean. When that happens, answers sound correct but lack real explanation. This is why many students benefit from guidance from a primary science tutor, especially when learning how to turn understanding into clear exam answers.

How CER helps you avoid losing “easy” marks

Many marks in open-ended questions are lost not because the student does not know the answer, but because the explanation is incomplete or poorly structured.

CER helps you:

• Stay focused on the question.

• Include evidence instead of general statements.

• Explain concepts clearly, even in simple language.

When your answer follows a logical flow, markers can easily see where to award marks. You are less likely to miss out on marks you actually deserve.

Applying CER to common PSLE-style questions

Let’s look at a typical question:

“Explain why the plant placed near the window grew taller than the plant kept in the cupboard.”

Using CER:

• Claim: The plant near the window grew taller because it received more light.

• Evidence: The window plant had sunlight, while the cupboard plant was kept in the dark.

• Reasoning: Plants need light to make food through photosynthesis, which helps them grow.

Notice how this answer is simple, clear, and concept-based. No complicated vocabulary is needed, yet it still shows solid understanding.

Practising CER the right way

Understanding CER is one thing, but applying it under exam conditions takes practice. Writing full explanations, checking whether your reasoning makes sense, and learning how to be concise are skills that improve over time.

Good practice questions, guided feedback, and exposure to different question types make a big difference. This is also where habits outside the classroom matter. A consistent reading habit helps enhance science grades because it improves comprehension and familiarity with scientific explanations.

Building confidence for secondary school science

Although PSLE is a primary-level exam, the skills you learn now carry over into secondary school. Lower secondary science places even more emphasis on explanations, experiments, and reasoning.

Students who are comfortable explaining concepts clearly tend to adapt better later on. CER is not just an exam trick, but a thinking skill that supports long-term learning.

Conclusion

Open-ended science questions do not have to feel like a guessing game. When you focus on understanding concepts and use a clear structure like CER, your answers become more confident and organised.

Heuristics Science supports students through both primary and secondary science tuition in Singapore by teaching them how to answer questions clearly using guided practice and practical applications. With the right support and approach, science becomes less about stress and more about understanding how the world works.