Welcome back to our Examination Paper Analysis series!

Since the SA2 examinations are around the corner, today’s analysis will be based on the **2018 Wellington Primary School (WPS) P5 SA2** examination.

As per usual, I will be sharing with you the topic weightage in the paper, as well as discussing 2 interesting questions. Hope this helps!

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**Topic Weightage in The 2018 WPS P5 SA2 Science Examination Paper**

**Let us recap the topics that are commonly taught in the P5 curriculum:**

- Cells
- Water Cycle
- Human/Animal Reproductive System
- Plant Reproductive System/Plant Cycle
- Electricity
- Circulatory System & Respiratory System

**Here are the topics that are commonly taught in the P3 and P4 curriculum:**

- Diversity
- Materials
- Animal Life Cycles
- Plants including Plant Life Cycle
- Body Systems (Digestive System & simple summary on the 5 Body Systems)
- Magnets
- Matter
- Light Energy
- Heat Energy

As **Electricity** is a major topic in the P5 curriculum, it is not surprising that it is being tested by the most number of questions (10 questions; 6 MCQs & 4 OEQs) in this paper.

In second place, we have **Plant Cycle**, which includes questions testing on everything about Plants (7 questions).

In third place, there is a tie between **Body Systems** and **Heat Energy**, which both have 5 questions each.

If your child would like more question exposure on these topics, the 2018 WPS P5 SA2 paper will be ideal for your child to practise on!

If your child wants to work on questions testing the topics of **Animal Life Cycles **or **Light Energy**, I am afraid that this paper will not be suitable as there are no questions on these 2 topics.

**Here’s A Summary**

__ The table below is a summary of the topical weightage in the paper.__

We have always placed more focus on analysing open-ended questions (OEQs) in the previous articles from the examination paper analysis series. Today’s analysis differs slightly as we will be placing more emphasis on analysing multiple-choice questions (MCQs).

We will be discussing a question on **Heat Energy **(Q20) and a question that tests on both **Matter** and **Magnets** (Q18).

Let us first take a look at the question on Heat Energy.

**Let’s Start With Question 20**

**Thought Process**

This is actually a very commonly tested concept of “Expansion & Contraction” in Heat Energy, even at a Primary 4 level.

However, this question is of greater difficulty as it differs slightly from the usual questions that examiners set.

Typically, examiners want students to explain the importance of the gaps between railway tracks and/or the reason behind the loosely hung electrical cables between the poles.

This question provides the size of the gaps at different times of the day and requires students to match the correct time of the day to the size of the gap.

In order to answer this question, let us first understand the **reason behind the gaps** on railway tracks.

On a hot day, the railway track gains heat from the sun/warmer surrounding air to expand and increase in length/volume. Without gaps, the railway tracks would have no space to expand. Thus, the tracks will buckle and become damaged. When trains move over the buckled tracks, they may derail, resulting in loss of lives.

Hence, the purpose of the gaps is to **provide space for the tracks to gain heat from the sun/warmer surrounding air to expand and increase in length/volume, without buckling**.

With this understanding, let us now take a closer look at this question.

The question states that there is a gap of 2cm and a gap of 2.5cm at different times of the day. When the gap is smaller at 2cm, this means that the railway tracks expanded more and have moved closer to each other as compared to when the gap is at 2.5cm. This means that the temperature when the gap is at 2cm must be higher than the temperature when the gap is at 2.5cm.

**Let’s Compare The Four Options**

**How To Interpret This:**

Using Option (1) as an example, the temperature of the surrounding air at 12pm is hotter than the temperature of the surrounding air at 1am. Thus, 12pm is labelled as “Hotter” and 1am is labelled as “Cooler”.

**Here’s The Answer**

Thus, we can conclude that the answer is **Option (1)**.

**Let’s Take A Look At Question 18**

**Thought Process**

This question requires students to integrate the key concepts from the topics of Matter and Magnets.

__Key Concept from Matter: Comparing Mass Using A Balancing Beam__

If 2 objects are placed on both ends of the plastic rod and they have the same mass, the plastic rod will be balanced. If one object has a greater mass than the other object, the plastic rod will tilt downwards towards the side with the heavier object.

**Not taking into account the presence of other objects like magnet Y.*

__Key Concept from Magnets: Attraction & Repulsion__

__When the like poles of 2 magnets are facing each other, they will repel and move away from each other.__

When the unlike poles of 2 magnets are facing each other, they will attract and move towards each other.

Let us now analyse the question.

We can see from the diagram that the North-pole of magnet X is facing the North-pole of magnet Y. Since the like poles of magnets X and Y are facing each other, they will repel.

Thus, magnet Y will exert an upwards push force on magnet X. As a result of this upwards push force acting on magnet X, the plastic rod is balanced.

To understand this from a mathematical point of view, this shows that: (Do note that I used mass/weight interchangeably here for simplified understanding)

**Weight of Object T = Weight of Magnet X – Force of Repulsion**

If we rearrange the equation, we can see that:

**Weight of Magnet X = Weight of Object T + Force of Repulsion**

**Here’s The Answer**

Hence, the mass of the object T is less than the mass of magnet X, which is 50g.

The answer is Option (3).

**Moving Forward**

I hope this article helped you gain a better understanding of the two questions we’ve discussed.

Continue to keep a lookout for our new articles!

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