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Posted on : 2011-04-08 

Part 2
Previously, we have shared some tips on good study habits and how to tackle MCQ questions to achieve good grades for PSLE Science. Now let's explore some tips on how to take on another type of questions in the examination - Open-ended Questions

Open-ended Questions

  • For open-ended questions, circle the keywords in each question to help you to focus on what is being asked. It is important that you understand the question.

What are the products formed during photosynthesis?

To answer such a question, first, identify the keywords. The keywords are ‘photosynthesis’ and ‘products’.
When you see ‘photosynthesis’, you should recall what this word means. Photosynthesis is a process whereby plants make food in the presence of sunlight. The question is asking about the products of photosynthesis. This means that you have to provide more than one answer to the question.
Recall that food (sugar) is made in plants and oxygen is given out during photosynthesis to replenish the air. Hence, the answers are sugarand oxygen.
  • Note the question terms used in the question. This will help you understand what answer is required of you in order to score full marks for that particular question. 


When a magnet is placed near object X, object X does not move. When the magnet is placed near object Y, object Y moves away from it.

(a)  Explain why object X does not move when the magnet is placed near it.

(b)  State the possible materials that can be used to make object Y.

For (a), the question term used is ‘Explain’. ‘Explain’ means that you have to give reasons for the observation stated.
The observation is that object X does not move. Object X does not move because it is neither a magnet nor an object made of magnetic material. If object X is a magnet or a magnetic material, it will either be attracted to or be repelled by the magnet.
Thus, the correct answer is ‘Object X is made of a non-magnetic material, hence it is not affected by the magnet.
For (b), the question term used is ‘State’. State means that you only need to write short answers, meaning a few words or short phrases.
Since object Y moves away from the magnet, object Y is also a magnet. Magnets are made of or can be made by one of the four types of magnetic materials. Hence, the answer for (b) is ‘Iron, steel, nickel or cobalt’.
  • It is always good to be concise in your answer. Using the correct keywords in your answer will help you score the marks allocated.

50 cmof air is being pumped into a 30 cm3 container.

(a)  What is the volume of air inside the container?

(b)  Explain your answer in (a).

For (a), the question asks about the property of air (gas). Recall that air does not have a fixed volume and a fixed shape and so the volume of air inside the container is 30 cm3 instead of 50 cm3.

For (b), the question is asking for a reason. As mentioned earlier, air does not have a fixed volume and a fixed shape. We can only see the shape of the air changing when it is being transferred from one container to another of a different shape. Hence, we cannot write ‘Air does not have a fixed shape’ as the answer.
Air does not have a fixed volume, hence its volume changes from 50 cm3 to 30 cm3. Writing ‘Air does not have a fixed volume’ as the answer is not wrong, but there is a better word to use for this question. The keywords are ‘can be compressed’ or ‘compressible’. Air does not have a fixed volume and hence it can be compressed.
The concise answer to this question would be ‘Air can be compressed’ or ‘Air is compressible’.
Do note that constant revision is also essential in preparing for the examination. Hopefully, with these tips in mind, you will find that Science is not as difficult as you might think and will be on your way to achieve your ideal grade.
Written by: Tan Chiang Heng
Click here for Part 1 of the article

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