Q&A - PSLE Science

[wkong]

This question is abit tricky, should it be (2) or (3)? Which is the keyword that gives the hint of the answer?



http://postimage.org/image/w313pnlw/

[ADoc]

anneshirleygilbert:

Thank you, ADoc for the added info. From the time I learned language and articulation, I was always taught, \"We see the table, we see the rainbow .....\" Now, in Spore Primary Science, my daughter says, \"Light falls on the objects and then bounces off into our eyes, causing us to see.\" This makes so much sense! and what a reverse in the direction of perspective! Perhaps, someday, we should start teaching children this concept from the very beginning of their lives. That should erase a lot of confusion, don't you think? Thanks, ADoc for that question.

haha! Absolutely!
Then again, as math & science become our kids' lingua franca, that's also when they begin to shed the child in them (which is one of most valuable gifts that any can have)...what a pity!

(kids shouting in the background) \"That's life cycle for you!\"

[ADoc]

wkong:

Thanks ADoc for the explanation of the questions I posted earlier on.


I have another question that I need advice:

The answer is (3) or (4)?


http://postimage.org/image/1sz47y62s/

Hi! The answer would be (2). And this sort of question is always highly contentious in the sense that students can be as creative as they can and think of many possible combination of energy conversions.

Let's take it as option (1) is definitely out. The rest of the three are just as equally valid. The debate is really what goes on in the middle.
The way I guide my students is: the final (or desired outcome) energy must always be stated, whereas the start can sometimes be skipped to the next energy conversion depending on the question. What goes on in between must always contain the main components of the equipment.

For this question, we have no problem see that the desired outcome is the sound produced by the bell, hence sound energy. The start can be potential (chemical) or electrical energy. The main components are the solenoid (magnetic energy) ---> attracting the iron bar and hammer as a single component (kinetic energy).

option (3) misses out on the important aspect of a bell which is the magnetic energy.

option (4) misses out the important action of the bell which is essentially the movement (kinetic) that causes the hammer to strike the bell.

Of course, we can always list heat energy as well, but that's unnecessary in this case as it's not the desired outcome, unless the question explicitly states so.

If this wasn't an MCQ question, I would list the energy conversion diagram as:

chemical potential --> electrical --> magnetic ---> kinetic ---> sound

any other views from other forum-ers?
cheers!

[tianzhu]

wkong:

Thanks ADoc for the explanation of the questions I posted earlier on.


I have another question that I need advice:

The answer is (3) or (4)?


http://postimage.org/image/1sz47y62s/

Hi

I cannot remember seeing term like magnetic energy in PSLE science under the topic of Energy.

The forms of energy are Potential, Kinetic, Heat, Light, Sound and Electricity.

Best wishes

[anneshirleygilbert]

Need some help for this question on heat:


In which of the following will the milk gain the most amount of heat?

1. 50 ml of milk at 25 degrees C in a trough of water at 50 degrees C.
2. 50 ml of milk at 50 degrees C in a trough of water at 25 degrees C.
3. 40 ml of milk at 50 degrees C in a trough of water at 25 degrees C.
4. 40 ml of milk at 25 degrees C in a trough of water at 50 degrees C.

The given answer is (1), but why not (4)? Is it because (1) has a greater volume of milk? Pls help. I’m kind of muddled.

[ADoc]

tianzhu:

wkong:

Thanks ADoc for the explanation of the questions I posted earlier on.


I have another question that I need advice:

The answer is (3) or (4)?


http://postimage.org/image/1sz47y62s/

Hi

I cannot remember seeing term like magnetic energy in PSLE science under the topic of Energy.

The forms of energy are Potential, Kinetic, Heat, Light, Sound and Electricity.

Best wishes

Hi tianzhu! You're absolutely right about the 6 forms of energy that the primary curriculum is required to impart.

There are some schools that do teach other forms of energy such as tidal, wind, mechanical, even nuclear. Their teaching is skewed towards that most forms of energy can be traced to a single source. In addition, students are taught that energy classificatons are mere (human) categorisations and are usually subsets of each other to be precise. The concept that energy is the ability to do work or that energy is required to make things move or do work is especially emphasised. This concept is really a powerful one such that it tinkles the student's mind that as long as something moves, there must be at least one energy involved.

Having said these, I am not sure of the setter's intention and the origin of the question. If the intention is to (1) identify the order of enegy conversion, (2) identify the 6 forms of energy that are \"taught\", then the answer is obvious. Else this question will be finding its place in the sacred basket of ambiguous & contentious questions. haha!

By the way, I totally for \"primary questions use primary knowledge & syllabus\". That's only fair for the kids. The onus lies with the setter to ensure that the options for answers must be within primary syllabus as well. If not, it will just invite fires.

Hi KWong, what's your kid's teacher's \"answer\" and explanation? tks!

cheers!

[ADoc]

anneshirleygilbert:

Need some help for this question on heat:


In which of the following will the milk gain the most amount of heat?

1. 50 ml of milk at 25 degrees C in a trough of water at 50 degrees C.
2. 50 ml of milk at 50 degrees C in a trough of water at 25 degrees C.
3. 40 ml of milk at 50 degrees C in a trough of water at 25 degrees C.
4. 40 ml of milk at 25 degrees C in a trough of water at 50 degrees C.

The given answer is (1), but why not (4)? Is it because (1) has a greater volume of milk? Pls help. I'm kind of muddled.

Hi there!
I agree ans should be (1). For the same temperature difference, the greater the amount of a substance (volume or mass), the more energy it will (have to) gain in order to be raised by the same amount of temperature.

In our usual daily experience, imagine having two cups of hot kopi (aka trough) with an ice cube (aka milk) and another ice cube double the size. Which cup of kopi will be colder (aka lose more heat to milk, in other words milk gain more heat)?

Experience tells us that the kopi with the bigger ice cube would be colder. Drawing similarity: bigger ice cube = larger volume of milk; colder kopi = greater heat loss which means greater heat gain by the larger volume of milk.

In secondary physics, this concept is explained via heat capacity.

Hope this kopi experience will be useful to you when explaining to your kid.

[ChiefKiasu]

ADoc:

anneshirleygilbert:

Need some help for this question on heat:


In which of the following will the milk gain the most amount of heat?

1. 50 ml of milk at 25 degrees C in a trough of water at 50 degrees C.
2. 50 ml of milk at 50 degrees C in a trough of water at 25 degrees C.
3. 40 ml of milk at 50 degrees C in a trough of water at 25 degrees C.
4. 40 ml of milk at 25 degrees C in a trough of water at 50 degrees C.

The given answer is (1), but why not (4)? Is it because (1) has a greater volume of milk? Pls help. I'm kind of muddled.

Hi there!
I agree ans should be (1). For the same temperature difference, the greater the amount of a substance (volume or mass), the more energy it will (have to) gain in order to be raised by the same amount of temperature.

In our usual daily experience, imagine having two cups of hot kopi (aka trough) with an ice cube (aka milk) and another ice cube double the size. Which cup of kopi will be colder (aka lose more heat to milk, in other words milk gain more heat)?

Experience tells us that the kopi with the bigger ice cube would be colder. Drawing similarity: bigger ice cube = larger volume of milk; colder kopi = greater heat loss which means greater heat gain by the larger volume of milk.

In secondary physics, this concept is explained via heat capacity.

Hope this kopi experience will be useful to you when explaining to your kid.

Great answer. How about repurposing the same question in the following forms:
a. In which of the following will the milk experience the greatest temperature change? Ans: All of the above

b. In which of the following will the milk take the longest time to reach the temperature of the trough of water? Ans: (1) and (2)

[tianzhu]

wkong:

This question is abit tricky, should it be (2) or (3)? Which is the keyword that gives the hint of the answer?



http://postimage.org/image/w313pnlw/

Hi wkong

Good Morning.

I think we are advised to refrain from using the term “insulator of heat’ in PSLE science. If I remember correctly, there are some discussions in earlier posts.The term to use is 'poor conductor of heat'.

So, I would not consider (2)

(1) is out as copper is non magnetic.
(4) is out as well.

There only choice left is (3).

Best wishes

[atutor2001]

ChiefKiasu:

Great answer. How about repurposing the same question in the following forms:
a. In which of the following will the milk experience the greatest temperature change? Ans: All of the above

b. In which of the following will the milk take the longest time to reach the temperature of the trough of water? Ans: (1) and (2)

Wow Chief, don't be so cruel leh. The original question is already tough enough and you have up the level of complexity. :lol:

Can help to explain your answers? Thanks