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PSLE Science: Top 5 Common Mistakes in ‘Water & Changes in States’ & ‘Water Cycle’ Questions


PSLE Science

As parents of Primary 6 students gearing up for the Primary School Leaving Examination (PSLE), understanding the common mistakes that students make in the “Water & Changes in States” and “Water Cycle” topics can be instrumental in ensuring your child’s success.


This particular subject often requires a more in-depth analysis of concepts, which can lead to some misconceptions if not addressed carefully. In this article, we’ll discuss the top 5 common mistakes students tend to make in PSLE science questions related to water cycles and state changes and how to avoid them, providing valuable insights to help your child excel in this critical examination.


1. Mistake: “Clouds Are Gases”


Condensation is the scientific term for when water vapour changes into tiny liquid droplets, coming together to create clouds. Sometimes, students might think that clouds are only made of water vapor, forgetting that condensation plays a really important role in making clouds. Now, think about clouds.


They’re not just made of invisible water vapor. Nope, they’re actually made of these super tiny water droplets! And guess what? These droplets form when water vapour cools down and turns back into water. This process is called condensation. So, when you see clouds in the sky, you’re actually looking at many of these tiny water droplets that formed due to condensation.


2. Mistake: Assuming No Heat Gain/Loss when Temperature Remains Constant


Students often tend to get confused and believe that when the temperature stays the same, it automatically means there’s no change in the heat being added or taken away.


But here’s the thing: it’s not always the case! To really understand what’s going on, students should closely examine what occurs during the parts of the graph where the temperature remains constant. Let’s break it down with an example from a graph:


Assuming No Heat Gain

At parts AB and CD, the temperature stayed constant/same. Students sometimes make the error of believing that there is no heat gain/loss at AB and CD. The true answer, however, is that there is heat gain at both AB and CD despite their constant temperatures.


Steps:


  1. Determine what activities are taking place; an increase in temperature in BC indicates that the material is being heated up. This indicates that when AB is melting, CD is boiling.

  2. Keep in mind that whether melting, boiling, or freezing occurs, the temperature remains constant because the heat energy acquired is required to convert the state from solid to liquid (at AB) and from liquid to gas (at CD).

  3. Remember that heat gain is necessary for melting or boiling, whereas heat loss is required for freezing.

  4. As a result, AB and CD exhibit heat gain.


Missing Essential Keywords in Water Cycle Explanations


3. Mistake: Missing Essential Keywords in Water Cycle Explanations

There are two types of questions involving evaporation in the water cycle, and depending on the question type, there are specific keywords that we must include or don’t need to include.


For example:


 two types of questions involving evaporation in the water cycle

As we can see from the diagram, this question started off with hot water. In this case, they ask to explain/describe how water droplets are formed since the water is already hot. Students are not required to mention “gain heat from __________” as the water is already hot and is not gaining any more heat, and there is no heat source either.


Thus, the model answer will be:


Water in the beaker evaporated into warmer water vapour, which came into contact with the cooler surface of the metal sheet, lost heat, and condensed into water droplets.


Water in the beaker evaporated into warmer water vapour

As we can see from the diagram, this question shows a Bunsen burner (heat source). In this case, there is a heat source and the water did not indicate that it is hot. Students are required to mention “gain heat from __________”.


Thus, the model answer will be:


Water in beaker A gained heat from the Bunsen burner and evaporated into warmer water vapour, which came into contact with the cooler surface of the metal sheet, lost heat, and condensed into water droplets.


verlooking the Evaporation Section in Water Droplet Formation


4. Mistake: Overlooking the Evaporation Section in Water Droplet Formation Explanations


Missing out on the evaporation section when explaining how water droplets are formed. There are two types of water cycle questions that students have to look out for to determine whether there is a need to mention evaporation or there isn’t a need to mention evaporation.

For example:


Water Droplet Formation

As we can see from the diagram, this question shows a water body (source of water), which is water at 90 ͦ C. In this case, since there is a water body, the process of evaporation MUST be mentioned when talking about water formation.

Thus, the model answer will be:


Water in the beaker evaporated into warmer water vapor, which came into contact with the cooler underside of the glass cover, lost heat, and condensed into water droplets.


Water in the beaker evaporated into warmer water vapor

As we can see from the diagram, this question did not show any water body (source of water). In this case, since there is no water body, the process of evaporation does not need to be mentioned in the answer, and students are supposed to start with condensation.


Thus, the model answer will be:


The warmer water vapour in the surrounding air came into contact with the cooler outer surface of the beaker, lost heat, and condensed into water droplets.


5. Mistake: Using the Wrong Keywords for Water Formation Explanations


Students tend to not read the question carefully and mention the wrong process in water formation questions.


Using the Wrong Keywords for Water Formation

In the above question, the question mentioned that the liquid was seen bubbling, this indicates that boiling has occurred as during evaporation there will not be bubbles forming.


Thus, when describing water formation, students need to mention boiling and steam instead of evaporation and water vapour.


Thus, the model answer will be:


Water in the muddy seawater in beaker A gained heat from the Bunsen burner and boiled into steam, which came into contact with the cooler surface of the metal sheet, lost heat and condensed into water droplets and dripped into beaker B.


Water in the muddy seawater in beaker A gained heat from the Bunsen burner and boiled into steam

We will have to mention evaporation and water vapour instead.


The model answer will be:


Water in the muddy seawater in beaker A gained heat from the Bunsen burner and evaporated into water vapour, which came into contact with the cooler surface of the metal sheet, lost heat and condensed into water droplets and dripped into beaker B.


Water in the muddy seawater in beaker A gained heat from the Bunsen burner

As your child prepares for the challenging PSLE Science examination, being aware of these common mistakes and their solutions can make a significant difference. The “Primary Science Water Cycle” topic requires a precise understanding of processes, terminology, and context. Encourage your child to approach questions methodically, analysing the provided information carefully before crafting their answers.


Remind them to read questions thoroughly, identifying any hints regarding processes, temperatures, or keywords that should be included in their responses. Regular practice and reviewing sample questions can help them internalise these concepts and apply them effectively during the examination.


By providing guidance and support, you can help your Primary 6 student navigate the water cycle for Primary Science successfully. The insights shared in this article will empower them to avoid common mistakes, grasp challenging concepts, and confidently approach “Water & Changes in States” and “Water Cycle” questions, ultimately contributing to their overall success in the PSLE examination.



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