Simple Machines - The Movable Pulley

This article was first published on 3 Sep 2008.

One of the functions of simple machines is to lighten our workload. A small effort can move a greater load. What is sacrificed is that the distance moved by the effort is greater than the distance moved by the load.

As an example, we will take a look at the movable pulley. So how does a movable pulley help to lighten our work?

Remember that in order to be able to move a load that is greater than the effort, the distance moved by the effort has to be greater than the distance moved by the load.



With reference to the diagram above:-

Pulley A - The distance from the pulley to the ceiling is 2m. This means that the cable attached to the pulley is also 2m.

Pulley B – The distance moved by the effort is 2 m. However, the load moves only 1 m from the original position of the pulley. This is confirmed by …. 2-m cable divided by 2 = 1m, which means that the distance from the pulley to the ceiling is 1m. Hence, the distance from the pulley now, is 1 m from where it was originally.

Since the effort moved twice the distance moved by the load, only ½ the effort is needed to raise the load. Hence if the load weighs 10 kg, an effort of slightly over 5 kg only is needed to move the load.

Simple Machines – The Inclined Plane

This article was originally published in Oct 2008.

As with all machines, if we want the force exerted by the effort to be less than the force exerted by the load, the distance travelled by the effort has to be more than the distance travelled by the load.

Below are 4 illustrations how the inclined plane works.



The more gradual the slope, the greater the distance travelled by the effort compared to the distance travelled by the load. This means that the more gradual the slope, the less effort is needed to move the load.

Examples of applications of the ramp in real life – wheelchair ramps for the disabled, gradual and winding slopes of a road found in mountainous terrain (e.g. roads to Gentling Highlands or Cameron Highlands).



It can be noted that the ‘sharper’ the wedge, the less the effort is needed because for the same distance travelled by the effort, the distance moved by the load is now less.

Examples of applications of the wedge in real life – axe head, blades of knives, metal wedges for prying open flanges of pipes in heavy industries.



Fig 1 - For every 1 turn the screw makes, the screw is driven down by the distance of ‘1 pitch’. Hence, the more gradual the slope of the thread, the smaller the distance it will be between 2 threads, as shown in Fig 2.

Fig 2 - the distance travelled by the load is less than in Fig 1, although in both cases, the effort moves by the same one turn. Since the load moves less in Fig 2, less effort is also needed.

In conclusion, for screws, the more the number of threads there is, OR the smaller the pitch, OR the more gradual the slope of the threads, the less the effort is needed to move the load.



Again, like the screw, the smaller the pitch, the less the ends of the ‘V’ move towards each other, which also means the less the distance the load moves.

Like the screw, for the screw jack, the more the number of threads there is, OR the smaller the pitch, OR the more gradual the slope of the threads, the less effort is needed to move the load.

Take note that for the screw jack, while the mechanism of the inclined plane is used to lift the vehicle off the ground, the handle of the screw jack works on the principle of the wheel and axle. In this case, the handle is the wheel, while the screw of the jack (the part with the threads) is the axle.


Important note to parents and students – The purpose of the above 4 illustrations is to help students understand the mechanics of the inclined plane. Most schools’ practice papers and science textbooks do not use the terms ‘pitch’ or ‘threads’. Those terms are technical terms used in the heavy and light industries.

In trying to make the illustration as simple as possible, I have found that I cannot avoid using those technical terms. The use of the above terms is to assist the student (or parent) to understand the mechanics of screws and screw jacks.

Take note that markers who will be marking your Science PSLE Paper, in all likelihood have been teachers all their lives and may not have worked in industries before, and would probably not be familiar with the terms ‘pitch’ and ‘threads’.

In other words, it is highly advised that you do not use the terms ‘pitch’ and ‘threads’, unless you are able to draw and label the diagrams as accurately as the above.

Common Errors and confusion – Cell Division

Cell division is the process where the cell splits into two new cells. What is the purpose of cell division? That depends on: If the organism is a multi-cellular organism, (for example a cat, a mango tree, a mushroom) the purpose is for growth and replacement of old cells. A kitten needs to grow into a cat. A seedling needs to grow into an adult plant. Hence, cells need to go through the process of cell division so that the organism can grow. 

Cell division also helps replace older cells that die. If the organism is a single-cellular organism, (for example paramecium, bacterium) the purpose is for reproduction. All living things reproduce more of their own kind for the continuity of their species. 

The most common confusion among students is that they erroneously think that the purpose of cell division is for growth, replacement of old cells and reproduction for all organisms. This concept is WRONG. Below, is a table that summarises the right and wrong concepts of the function of cell division.

  

The Three States of Water

Most PSLE students know that water exists in three states – solid, liquid and gas. Most students also know that the ‘magic numbers’ are ‘0’ and ‘100’ deg Celsius, because that is the temperature at which water changes its state.

Students also know that ice exists at 0 deg C and below, while steam exists at 100 deg C and above.

However, quite a few students get confused, when the temperature is at or between 0 and 100 deg Celsius. Some students get the impression that water exists in liquid form only when the temperature is at or between 0 and 100 deg C. This concept is wrong.

At or between 0 to 100 deg C, water can exist in two forms – liquid (as in lakes, rivers) and gas (water vapour). Below is a diagram to illustrate the states of water, in relation to the temperature.



Simply put,
Solid - At 0 deg C and below.
Liquid – At and between 0 and 100 deg C.
Gas – At 0 deg C and above.


Important and useful point to note –

Because water can exist in 2 forms (liquid and gas) from 0 to 100 deg C, we have evaporation, condensation in this world and hence, the very critical Water Cycle, which is so important to life on earth.

If water exists only as liquid between 0 to 100 deg C, it will not evaporate to form water vapour, then condense to form clouds, and eventually fall back to earth as rain.

This wide range of 0 to 100 deg C, where water exists in 2 forms is unique, unlike many other substances, where at a given temperature, it exists only in one form.

Summary – Water exists in two forms (liquid and gas) from 0 to 100 deg C and NOT in liquid form only.

Common Errors and Confusion – “ovary” and “spores”

It is a bit unfortunate that both the reproductive parts of the female human and the female part of the flower have the same name, “ovary”. Because both have the same name, spelling and the same way they are pronounced, some students end up confused.

Ovary in a flower refers to the female reproductive part of the flower. The ovary in this case, will develop into the fruit after fertilization. The ovary of the flower is illustrated as shown below.



Ovary in the human female on the other hand, is the reproductive part of the female where eggs are produced. The ovary in the human female is illustrated as shown below.



Another confusion which is caused by the same term, is “spores”. Spores are produced by ferns and mushrooms for the purpose of reproduction. Again, because of the same name, some students get confused that mushrooms and ferns are plants. This is not correct. Ferns are plants but mushrooms are fungi. Only plants make their own food. Mushrooms feed on dead matter - eg rotting logs.

Majestic Niagara Falls

Besides being a tourist attraction, Niagara Falls is also known to generate electricity for both Canada and US.

Hydro Electric Power is electricity generated by water. A dam is built to increase the height of the water. As the height of the water increases, gravitational potential energy increases. Water at the bottom of the dam thus experiences high pressure. This causes the water to be released at a high speed, with a lot of kinetic energy.

The kinetic energy is then used to turn the turbine, which then turns the generator to produce electricity.

Pictures of Niagara Falls.

Rainbow Falls, on the US side of the border

Horseshoe Falls, on the Canadian side of the border. Yes, we all got wet as the boat approached the falls.

A couple more shots of the falls below.







Picture shot of the dam at the Hydro Electric Power Plant, on the Canadian side of the border. (below)



The dam is situated a few kilometres downstream of the falls.

That's all for now.

In the countryside – Midlands, Ontario, Canada

Trees and other plants play an important part in our environment. When they make their own food through photosynthesis, they produce oxygen for all living things to respire.


In the winter, most trees lose their leaves.


In the summer, green leaves are everywhere in sight.



Earthworms are important to the environment. They help aerate the soil and aid plants by dragging leaves into the soil – which will serve as nutrients for the plants.




Here are some other things you can find in Midlands. Fairytale Land!






That's all for now.

Holiday Update - Downtown Toronto, Ontario, Canada

It's not just cold in Toronto, the air is also very dry. That means humidity is low. Guess what happens to the rate of evaporation when humidity is low, students. Remember your science? Yes, the rate of evaporation is higher when humidity is lower.

That is correct. That means your clothes dry faster, and your body loses a lot of water through perspiration. Toronto is the first place I've been where the average daily temperature is around 12 deg C, yet even after drinking over a 2 litres of water, I still feel thirsty. All other cities/countries where I have had to drink lots of water, had average daily temperatures above 30 deg C.

Well, that is Science in action - the lower the humidity, the higher the rate of evaporation.

That's the PSLE Science part. Here is the holiday part. Toronto is a big city. You don't have to miss your home food, because Chinatown in Toronto offers you value for money Asian food and spices. For those who prefer Indian food, there are also many outlets selling such food.

Here is a couple of Toronto photos.



Scenic view of Toronto Harbour View, from CN Tower, the world's highest free standing structure.



Downtown Toronto.

That's all for now.

Common Science Mistake – Internal and External Fertilisation

Fertilisation (in animals) is the process where the male sperm cell fuses with the female egg cell.

Internal fertilisation occurs when the male sperm cell fuses with the female egg cell, in the female’s body.

External fertilisation occurs when the male sperm cell fuses with the female egg cell, outside the female’s body.

The most common mistake made by students is that they believe internal fertilisation occurs in animals that give birth (example mammals) and external fertilisation occurs in animals that lay eggs (example birds and reptiles etc). This concept is wrong.

Internal fertilisation occurs in mammals, birds and reptiles.

In the case of mammals, fertilisation occurs in the female’s body. The new life develops inside the mother’s womb for most mammals.

In the case of birds and reptiles, fertilisation occurs inside the female’s body, and the fertilised egg is then laid. The new life develops outside the mother’s body.

In the case for amphibians and most fishes, fertilisation occurs outside the female’s body and the new life develops outside the mother’s body.

Below are some examples of internal and external fertilisation.

Water freezes below 0 deg Celsius

Interesting video showing water freezing in Newfoundland, Canada. The waves freeze upon impact!

The Four Seasons

PSLE Science textbooks explain that the Earth’s revolution round the Sun causes the 4 seasons. However, many of these books do not appear to explain that the tilt of the Earth’s axis is also a contributory factor.

In Figure 1 below, note that the Earth’s axis is not vertical but tilted at an angle away from the vertical line. The sun’s rays will cause half of the Earth to experience day, while the other half to experience night.

Figure 1



Imagine a place on Earth marked “A” in the Fig 1 above. "A" will experience night. As the Earth rotates, A will move towards A1. The dotted line between A and A1 is the path taken by the place marked “A”, as the Earth rotates.

Note that the dotted line between A and A1 has a longer period of day, as compared to the night. This causes the parts of the Earth marked between A to A1 to experience summer.

At the same time, the place on the Earth marked “B”, will move towards B1 as the Earth rotates. Also note that the dotted line between B and B1 has a longer period of night, as compared to the day. This causes the part of Earth marked between B to B1 to experience winter.

The Earth revolves round the sun once every year. This means that in 6 months, the sunlight will fall onto the Earth from the opposite direction.

Figure 2


In Figure 2, we have a different diagram showing the Earth 6 months later. Since the earth takes 12 months to revolve around the Sun, in 6 months, it makes only half a revolution. This causes the sunlight to fall onto the Earth from the opposite direction.

It can be seen that the parts of the Earth marked between A to A1 will now experience a longer period of night, as compared to the day. This now means that the parts of the Earth marked A to A1 will experience winter.

Again, at the same time, the parts between B and B1 will experience a longer period of day, as compared to the night and hence, will experience summer.

From these 2 diagrams, we can see that when the Northern hemisphere experiences summer, the Southern hemisphere will experience winter and vice-versa.

The 4 seasons is thus caused by the Earth's revolution around the Sun and the tilt of the Earth's axis.

Question on Phases of the Moon

In yesterday’s post, we created a 28-day chart in order to calculate the phases of the moon. In this post, we will apply what we have learnt to answer an actual Science question on phases of the moon.

Question

Rashid observed a full moon on 6 January. When will he most likely observe a full moon in February?

(1) 5 February
(2) 15 February
(3) 25 February
(4) 5 and 22 February

Using the 28-day chart, we count 28 days from 6 January.

28 + 6 = 34

Since January has 31 days, we minus 31 days.

34 – 31 ----> 3 February

Hence, Rashid would be likely to observe a full moon on 3 February. However, in the multiple choice question above, there is no 3 February. The closest date is 5 February. We therefore take the answer to be (1) 5 February.

Note: The answer (4) 5 and 22 February is not accepted because it takes 28 days for every full moon to appear and 22 February is only 17 days after 5 February.

Calculating the Phases of the Moon

The first Science topic taught in P5 in most schools is the Solar System. Of all sub-topics within this topic, Phases of the Moon gives students the most headache. Most students find difficulty in calculating the dates of the phases of the moon.

Here is a quick and simple method to make sure you get your dates right.

The moon revolves round the earth in 28-day cycles. In order to calculate the phases of the moon, we must therefore use a 28-day chart.

Note that in Figure 1 below, the beginning of the cycle is “Day 0” and ends at “Day 28”. It does not start at “Day 1” because if you were to start at Day 1 and end at Day 28, you will be creating a 27-day cycle instead of 28.

Days 0 represents the beginning of the cycle, while Day 28 represents the end of the cycle. It also must be noted that Day 0 of the current month is also Day 28 of the previous month. Likewise, Day 28 of the current month, is Day 0 of the next month.

Since Day 28 is the last day of the cycle, Day 14 is considered mid-cycle. Day 7 is hence right in middle of the beginning and mid-cycle, while Day 21 is the middle of the mid-cycle and the end of cycle.

Let us look at Figure 1 again. We start with a full moon at Day 0. At the end of the cycle, Day 28 will also have a full moon. Since Day 14 is mid-cycle, we will experience a new moon. Day 7 is between full moon and new moon, which means, we will experience half moon. Day 21 is between new moon and full moon, which also means we will experience half moon. Note that the half moon on Day 21 is a mirror image of Day 7’s half moon.


Figure 1


We can use actual dates to calculate. Let us suppose that a full moon was spotted on 26 July.

The next full moon will be 28 days from 26 July.

26 days + 28 days = 54 days.

But we know that there is no such thing as 54 days in a month. The last month was July, which has 31 days. We need to subtract 31 days from 54.

54 – 31 = 23

Therefore, the next full moon will be 23 August.

We can also calculate when the new moon will occur. A new moon occurs 14 days after a full moon. Hence,

26 days + 14 days = 40 days

40 – 31 = 9

Therefore, the new moon will occur on 9 Aug.

The half moons are 7 days from 26 July and 9 Aug.


Your turn now. Study Figure 2 below. Can you calculate the various dates? Try to make an attempt before checking the answers.

Figure 2


Answers for Figure 2:

Day 28 (next new moon) – 17 Dec.
Day 21 (half moon) - 10 Dec
Day 14 (full moon) – 3 Dec
Day 7 (half moon) - 26 Nov


Now try this one. No answers are given this time.



In tomorrow's post, we will take a look at an actual Science question on phases of the moon, and apply what we have learnt today, to answer that question.

=================

Update: Related post

Has the Mystery of Stonehenge been solved?

Watch this incredible video of how one man moves tons of blocks and created a mini Stonehenge in his backyard. The simplest of tools and knowledge of science were used - levers and gravity.




The topic of Simple Machines is taught in Primary 5 Science. It is a PSLE Science Topic.

One of the machines in the P5 Science syllabus is the lever. One of the functions of the lever is to help us move heavy objects. When the fulcrum is placed nearer to the load, compared to the effort, only a small effort is needed to move a larger load.



The video is a testimony that a small force can move heavy objects with the help of the simple lever.

Note that in the "see-saw" scene, which uses the lever principle, a small load is added on one side of the beam so that one side of the beam tilts towards the ground. The builder then raises the fulcrum and the beam is hence, raised.

In the scene where the beam is raised vertically, again, a small load is placed on one side of the beam, causing it to tilt towards the vertical position. Again, the principle of the lever is used.


In an earlier early scene where the builder moves the block in a circle, the principle of the lever is used yet again. He places a rock (the fulcrum) near the centre of the block (the load). In this case, the load is in between the fulcrum and the effort, unlike the other two examples, where the fulcrum is in the centre.

Again, note that the distance between the load and fulcrum is still much smaller than the distance between the effort and the fulcrum, enabling a small effort to move a much larger load.

An illustration is shown below.




Some information about Stonehenge.

http://dictionary.reference.com/browse/stonehenge

Stone·henge
a prehistoric monument on Salisbury Plain, Wiltshire, England, consisting of a large circle of megaliths surrounding a smaller circle and four massive trilithons; dating to late Neolithic and early Bronze Age times (c1700–1200 b.c.) and believed to have been connected with a sun cult or used for astronomical observation

Thinking Skills in Science

In this post, the topic of Magnets will be discussed to demonstrate how thinking skills is used.

Knowledge -
A magnet has two poles, a north-pole (N) and a south-pole (S). Like poles repel, while unlike poles attract.

Example:

Using the above knowledge to think and deduce –

Question:
Three metal bars A, B and C, are placed on a table. Only two of the metal bars are magnets, while the third is not. Hazri experimented the 3 metal bars as illustrated below.
Which of the two metal bars are magnets?



Answer: Metal Bars A and C are magnets. Metal Bar B is not.

Thinking Process –

When like poles of 2 magnets face each other, the magnets will repel. In Experiment 3, Metal Bars A and C repel. From this, we can conclude that the like poles of Metal Bars A and C were facing each other and hence, the bars repelled.

In Experiments 1 and 2, although the metal bars were attracted to each other, it does not mean that the bars are magnets. You need only one bar to be a magnet, and the other bar to be a non-magnet made from magnetic material (such as iron, steel or nickel), for the bars to be attracted to each other.

Can you solve this? Are you able to identify the pole that is marked “X” on Magnet E?

Answer: South-pole. Do you know why?

Here is the reason.

Handling “Section A” Questions for Science

In the post made on 8 Nov 2007, "Why do I keep losing marks for my Science?", we discussed how students can reduce loss of marks in Section B.

In this post, tips on how to minimise loss of marks in Section A will be discussed.

To get an A* for any subject at P5/P6, you will have to have to score above 90% of the maximum mark. To get a Band 1 for any subject at P3/P4, you will have to score at least 85% of the maximum mark. Science is no different.

The good news about science is that 60% (Section A) of your total score is based on Multiple Choice Questions (MCQ). The bad news is that this gives students (and parents) the false impression that Science is an “easy subject”.

What needs to be noted is that MCQ works both ways. You score the 2 full marks if you get the answer right, but get zero, if you get it wrong. There is no “partial mark” like 1 mark or half a mark.

This means that if you get 5 MCQs wrong, you will lose 10% of your marks, making it impossible for you to get that A*, no matter how well you did for your Section B.

A common question structure you will find, is like the example below.

---------
Question -

Which of the following statements about water are false?

(A) It has mass
(B) It has a definite shape
(C) It has no definite volume
(D) It can change from one state to another.

(1) A and D only
(2) B and C only
(3) C and D only
(4) A and B only
----------

Firstly, read the question properly. The question asks “Which of the following statements about water are false?” Many students tend to rush when they answer the question. They do not pay attention to the fact that the question is asking which statements in A,B,C,D are false and not which are true.

Secondly, make a list against the statements by placing a tick against the statement that is true, and placing a cross against the statements that are false. This way you will not be confused so easily.

Illustration


The question asks which of the above are false. By making a list, you have identified that B and C are false. Therefore, the correct choice is (2) – B and C only.

By placing a tick or a cross to identify which statement is true or false, you minimise your chances of making mistakes. This means you will do better for your MCQs in Section A, resulting in higher marks for your overall Science score.

Do not underestimate Section A Science. It may be the key to whether you score an A or an A*.

Remember, 5 MCQs wrong, and that A* will be out of your reach.

=======================

Related Article: Why do I keep losing marks for my Science?

The Consequential Question Trap

“The challenge, and it is often a difficult one, is for the question setter to pose the question in such a way that pupils with widely different background experiences will all build a sufficiently common mental picture and that mental picture is the same as the question setter’s mental picture” – Associate Prof Boo Hong Kwen, NIE (Straits Times Forum, 15 Oct 2004), commenting on the difficulty level of the PSLE 2004 Science Paper.

Question for students is, do you have a mental picture that is the same as the question setter’s mental picture?

--------------------------------------------

THE CONSEQUENTIAL QUESTION TRAP -
Why you should know what is in the question setter’s mind behind that Science question


Some students are puzzled, why they are marked wrong for certain Science questions, when the answer they give is right. This usually occurs when a set of questions is tied to a certain understanding of a theory.

A typical question (like the one illustrated below), is subdivided into Part (a) and Part (b). In this particular example, Part (a) tests on application of a theory, while Part (b) tests on knowledge of the theory itself.

In such an instance, if Part (a) is answered wrongly, Part (b) will also be marked wrong, regardless if the answer in Part (b) is answered correctly or not. The reason is because if the student gets Part (a) wrong, it tells the examiner that he/she does not understand the topic at all.

As such, even if Part (b) is answered correctly, it simply gives the examiner the impression that the student has probably just memorised the answer by heart, without understanding the theory involved.

Such a question is dubbed, The “Consequential Question Trap". It is considered a “trap” because students who learn science “by heart”, will usually fall for this kind of “trap” questions.

Below is an example of a typical “consequential question”, where Part (b) is dependent on Part (a). This example is a question taken from Primary 5 syllabus. The topic is “Electricity”.

--------------------------
Question
The diagram below shows four objects A, B, C and D connected to an electric circuit.



a) Which bulb(s) will light up?
b) What conclusion can you give regarding objects A, B, C and D?

Answer:
a) Bulbs 1, 2 and 4 only.
b) Steel rod and metal rulers are conductors of electricity, while rubber and plastic rods are not.
-------------------------

Part (a) tests the student’s application of theory, as to what are the consequences if you place a conductor or an insulator in an electrical circuit.

Part (b) tests on student’s knowledge on the characteristics of conductors and insulators.

To be able to answer Part (b) correctly, you must be able to identify which bulbs light up in Part (a).

If the student gets Part (a) wrong, it gives examiners the idea that he/she does not understand that the conductors will form a closed electrical circuit, resulting Bulbs 1, 2 and 4 to light up - while insulators will break the circuit, causing Bulb 3 to remain unlit.

From here, we can see that if Part (a) is answered wrongly, and if the student proceeds to answer Part (b) correctly, the impression given to examiners is that, the student has probably learnt by heart that “metals are conductors of electricity while plastic and rubber are not” in Part (b) - without understanding the theory that conductors conduct electricity, while insulators break the electrical circuit.

The above being the case, examiners will be highly suspicious as to how the student answered Part (b) correctly, when Part (a) has been answered wrongly!

A “consequential question” hence, has to be answered correctly from the start. If the initial part is answered wrongly, the subsequent answer(s) will be marked wrong, regardless how they have been answered.

The only way to get all parts right, is to study and understand its theory.

Learning “by heart” will not help!
---------------------------------------------
The above article was published in Excel!, a publication of Excel Eduservice in Oct 2004.
Publication Permit No: MITA (P) 297/03/2004
All rights reserved

Why do I keep losing marks for my Science?

That appears to be a very common question among students. Very often, they are puzzled why their friends are able to score 2 marks for a question, while they score only 1 or half mark, for what appears to be very similar answers given.

To understand how a student scores or loses marks, you must understand exactly what the examiner looks for, when he or she is marking the exam paper. Since most marks are lost in Section B, in this post, we will touch on Section B type questions only.


An examiner looks for two things in an answer, when he or she marks Section B questions. They are:

1. Key word(s)
2. Key concept(s)

Key word is the word that forms the main answer. This word tells the examiner if the student knows his or her work. If the key word is missing in the answer, the examiner will doubt that the student knows his or her work.

Key concept is the explanation of the concept that has been applied in the answer. It tells the examiner if the student understands the theory, concept and its application. If the key concept is missing in the answer, the examiner will believe that although the student has the answer, he or she does not have a full understanding of the concept(s) involved.

Below, is a Sample Question, followed by a Sample Answer.

==========================
Question - Raju put some ice into a glass of water. After a while, he noticed that water droplets started to appear on the outside of the glass. What caused the droplets of water to form?
(2 marks)





Sample Answer

When the water vapour in the air comes in contact with the cold surface of the glass, condensation takes place and water droplets are formed on the outside of the glass.
=========================

In the sample answer above, the key word is in red, while the key concept is in blue. The above answer is sufficient to score the 2 full marks.

The key word here is “condensation”. Without this word, it makes it very difficult for the examiner to give the student any mark, let alone full marks. This is because if “condensation” is missing, it tells the examiner that the student does not know what has been asked.

The key concept on the other hand, tells the examiner that the student knows that condensation has taken place, and more importantly, tells the examiner that the student knows under what conditions condensation takes place.

Hence, this question tests on knowledge (what is condensation) and understanding (how condensation changes the state of water and under what circumstances these changes will take place).

If the student simply answers “condensation” without further explanation, he/she will get less than 2 marks.

If the student explains the process of condensation, without mentioning the word “condensation”, then it all depends how convinced the examiner(s) is/are, that the student has understood the concept of condensation, by studying the answer given. However, more often than not, examiners will not be convinced.

Having mentioned that, even if the student does manage to convince the examiner(s), he/she will still not get the 2 full marks.

The student must give both, the key word and the key concept, to score full marks.

=======================================
The above article was published in Excel!, a publication of Excel Eduservice, in March 2006.
(Publication Permit No: MICA (P) 135/03/2006)
All rights reserved.
=======================================

Related article: Handling “Section A” Questions for Science