Q&A - PSLE Science

[ChiefKiasu]

anneshirleygilbert:

Got the earlier point, but not this one. How does impurities affect the change from liquid to solid? Can you please explain, even if it is beyond the PSLE syllabus. I'm curious.

It is in the PSLE syllabus. Impurities in water lowers its melting/freezing point. Milk is essentially water mixed with, um, the cow's natural goodness , ie. impurities. So milk will freeze at lower temperatures than pure water.

[ADoc]

anneshirleygilbert:

Hello ADoc,


4. Heat will stop travelling until the temperatures are the same (or equilibrium). I think you mean \"heat will continue travelling until the temperatures are the same (or equilibrium)\"??

Thanks for all your explanation. My daughter said she has benefited much.

hi anne! yup. that's what I meant. This is so embarrassing! Pardon my English..slight mishap there! ha!
cheers!

[anneshirleygilbert]

ADoc:

anneshirleygilbert:

Hello ADoc,


4. Heat will stop travelling until the temperatures are the same (or equilibrium). I think you mean \"heat will continue travelling until the temperatures are the same (or equilibrium)\"??

Thanks for all your explanation. My daughter said she has benefited much.

hi anne! yup. that's what I meant. This is so embarrassing! Pardon my English..slight mishap there! ha!
cheers!

Thank you, ADoc. No worries about your English. I think you do write very well. I mean, your ideas and explanation are very well expressed. It's just that sometimes our fingers don't co-operate too well with our mind. Have a good day!

[anneshirleygilbert]

[quote]It is in the PSLE syllabus. Impurities in water lowers its melting/freezing point. Milk is essentially water mixed with, um, the cow's natural goodness , ie. impurities. So milk will freeze at lower temperatures than pure water.[/quote]
Thank you, ChiefKiasu. Would you consider salt an impurity, too? Remember reading something about that. I'm not too much of a Science student, but am trying my best to read a little more widely to help my daughter.

[tianzhu]

Hi anneshirleygilbert


In PSLE science, I think it is good enough to know that the presence of impurities (salt) increases the boiling point and reduces the freezing (melting) point of water.

This link may help to address your query on the effect of salt on freezing/melting point of water.

http://www.worsleyschool.net/science/files/saltandfreezing/ofwater.html

Best wishes

[wkong]

ADoc:

tianzhu:

[quote=\"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![/quote]I just rec'd email from my DS Science teacher. Here is his reply:-

========================
The answer will have to be 3. There is chemical potential energy in the dry cells which will be converted to electrical energy when the circuit is closed. The striker will move as a result of kinetic energy and then sound and heat.

Number 3 best fit this conversion order.

There is no such thing as magnetic energy. Magnetism is a force.
========================

[atutor2001]

wkong:

========================
The answer will have to be 3. There is chemical potential energy in the dry cells which will be converted to electrical energy when the circuit is closed. The striker will move as a result of kinetic energy and then sound and heat.

Number 3 best fit this conversion order.

There is no such thing as magnetic energy. Magnetism is a force.
========================

Though I agree with the teacher's answer, I disagree with \"There is no such thing as magnetic energy\". There must be Energy before a force can be produced. If there is no magnetic energy, where does magnetic force come from? It is along similar concept that gravity / gravitation force is the result of Gravitational Potential Energy. Maybe the teacher felt that it should be called magnetic potential energy.

[ADoc]

wkong:

I just rec'd email from my DS Science teacher. Here is his reply:-

========================
The answer will have to be 3. There is chemical potential energy in the dry cells which will be converted to electrical energy when the circuit is closed. The striker will move as a result of kinetic energy and then sound and heat.

Number 3 best fit this conversion order.

There is no such thing as magnetic energy. Magnetism is a force.
========================

haha! I shan't debate with the \"teacher\". Without generalising or marginalising the great work of most MOE teachers, the quality of some and their \"world view\" of science in its totality (simplicity in essence) are rather disappointing. No cause for alarm just yet but small wonder that some parents are choosing to home-school their kids.

Notwithstanding the fact that most, if not all, primary teachers aren't required to major in the disciplines they are teaching unlike those in JC, some of them are even \"arrowed\" to teach certain subjects due to \"insufficient resources\". The remark \"there is no such thing as magnetic energy\" is worrying.

Just for info: primary teachers are required to teach up to 2-3 subjects; secondary up to 2; JC usually one (as you are required to major in your field of expertise). Oh well..I could be wrong.

Anyway, while some may argue (& I agree to a certain extent) there isn't a need to teach beyond the syllabus (in this case the definition of magnetic energy), the main concept of energy should be clarified and explained clearly so that students are able to recognise the different forms (& hence other possible forms) of energy not from what the syllabus or textbooks impart, but from its underlying concept. The saying of \"...teach a man to fish..\" couldn't be more apt in this case. And I must reiterate: to avoid ambiguity and unnecessary debate as to the answer to a question, make sure the options are reasonable and within syllabus.

Perhaps your DS can pose these questions to the teacher:
(1) A person is holding a magnet at a height, just above an iron paper clip. State the energy transfers when the height is such that the clip is attracted and \"moves\" up to the magnet. There's no electrical energy this time round. So where did the initial energy source come from? I hope the teacher won't say \"gravitational PE\" of the magnet due to its height gives it energy to attract the clip.
(2) If the doorbell in the figure hasn't the magnet, would it work?
(3) if it wouldn't, what would be primary function of the magnet?
(4) if \"energy is required to make things move\", what is causing the striker to move?
(5) what is the difference between \"the striker moves as a result of kinetic energy\" and \"the striker possesses kinetic energy because it moves\"?
(6) what is electromagnetic energy?
(7) what are Maxwell's equations?

alright...phew...i said my \"piece\" and this shall be my \"last piece\" of criticisms (constructive I hope).

cheers!

[atutor2001]

There is a problem of "incomplete" teaching in primary science concept and understanding because of the level of difficulty. Therefore, the science text needs to highlight at the end of every topic that what they have learnt are only the basics and there are many other aspects (perhaps giving some examples) so that children are more aware that science is much more than what they have learnt.


The real issue is that many science teachers have no love for science and simply give absolute answers like yes and no based on the given answer keys. The scenario of "maybe" is hardly used to stimulate the mind of the students.

[anneshirleygilbert]

tianzhu:

Hi anneshirleygilbert


In PSLE science, I think it is good enough to know that the presence of impurities (salt) increases the boiling point and reduces the freezing (melting) point of water.

This link may help to address your query on the effect of salt on freezing/melting point of water.

http://www.worsleyschool.net/science/files/saltandfreezing/ofwater.html

Best wishes

Thank you, tianzhu. The link is really an interesting read... and so helpful too. You are very resourceful. I read in the past posts that you also had a son who did his PSLE in 2009/2010? How diligent you were for his sake. I hope to do the same for my daughter. Thanks for all your help.