Q&A - PSLE Science

[anneshirleygilbert]

Many thanks, Atutor.

[anneshirleygilbert]

Can somebody pls help with this question?


We know :
The freezing point of water is 0 degrees.
The melting point of ice is 0 degrees.

Are the following two statements correct?
Water at 0 degrees is in the solid state.
Ice at 0 degrees is in the liquid state.

In view of the above, does it mean the following two statements are incorrect?
Water at 0 degrees is in the liquid state.
Ice are 0 degrees is in the solid state.

Thank you in advance.

[wkong]

May I know what should be the answer to this question? Thanks.



http://postimage.org/image/2v9wcto10/

[wkong]

Hi All,


I need help for the following question:-

What conclusion can be drawn from the experiment?

A: The lower the height of the marble, the lower the kinetic energy.
B: The greater the height of the marble, the greater the potential energy.
The greater the mass of the marble, the greater the potential energy.

(1) A only
(2) B only
(3) A and B only
(4) A, B and C


http://postimage.org/image/1t7qubr6s/

[ADoc]

anneshirleygilbert:

Can somebody pls help with this question?


We know :
The freezing point of water is 0 degrees.
The melting point of ice is 0 degrees.

Are the following two statements correct?
Water at 0 degrees is in the solid state.
Ice at 0 degrees is in the liquid state.

In view of the above, does it mean the following two statements are incorrect?
Water at 0 degrees is in the liquid state.
Ice are 0 degrees is in the solid state.

Thank you in advance.

Hi there! These are great questions! To avoid unnecessary debate from other friendly & knowledgeable forum-ers, let's keep the arguments within the context of Primary curriculum.

Are the following two statements correct?
Water at 0 degrees is in the solid state.
Ice at 0 degrees is in the liquid state.

These two statements are \"wrong\". Without further heat loss (freezing) or gain (melting), water & ice will just remain as water & ice at zero deg Celsius. For Primary's curriculum, these questions are meant to test the students' understanding of the process of melting & freezing, & the \"flat\" part of the heating or cooling curve: water starts to freeze or ice starts to melt at zero deg Celsius. For example, if we supply enough heat to a block of ice, it will start to melt (hence part liquid water) at zero deg Celsius. Conversely, if we remove enough heat, water still start to freeze (hence part solid water = ice) at zero deg Celsius. In both instances, we see that both contain part water (liquid) & part ice (solid) until the freezing or melting process is complete, i.e. water & ice can co-exist during its freezing or melting process (freezing or melting point).

In view of the above, does it mean the following two statements are incorrect?
Water at 0 degrees is in the liquid state.
Ice are 0 degrees is in the solid state.

These two statements are correct (unless the statements are further supplemented with phrases such as melting process / freezing process).

[ADoc]

wkong:

May I know what should be the answer to this question? Thanks.



http://postimage.org/image/2v9wcto10/

Hi! Ans would be (b) A was formed earlier than B.
We can eliminate the possibility of the rest of the three options since the question explicitly states that the \"...living conditions were similar...favourable to both...\" That means both communities are growing \"healthily\" & the only reason A has almost three times that of B must be it started earlier.

hope this is useful. cheers!

[ADoc]

wkong:

Hi All,


I need help for the following question:-

What conclusion can be drawn from the experiment?

A: The lower the height of the marble, the lower the kinetic energy.
B: The greater the height of the marble, the greater the potential energy.
The greater the mass of the marble, the greater the potential energy.

(1) A only
(2) B only
(3) A and B only
(4) A, B and C


http://postimage.org/image/1t7qubr6s/

Hi. Ans would be (2).
This question tests the student's understanding that energy is the ability to do work (hammering the nail into the plasticine in the experiment).
Since the question says that \"similar\" marbles --> we can ignore possible differences in mass. Hence, while C may be true in some instances, we are not able to conclude this from the experiment.

As for option A, there isn't any apparatus or \"result\" to measure and/or support such as conclusion.

That leaves us with the only option (2) which draws conclusion based on the variable (height) of the experiment and the inference of ability to do more work with more (potential) energy (a greater depth of nail being hammered into the plasticine).

[tisha]

ADoc:

anneshirleygilbert:

Can somebody pls help with this question?


We know :
The freezing point of water is 0 degrees.
The melting point of ice is 0 degrees.

Are the following two statements correct?
Water at 0 degrees is in the solid state.
Ice at 0 degrees is in the liquid state.

In view of the above, does it mean the following two statements are incorrect?
Water at 0 degrees is in the liquid state.
Ice are 0 degrees is in the solid state.

Thank you in advance.

Hi there! These are great questions! To avoid unnecessary debate from other friendly & knowledgeable forum-ers, let's keep the arguments within the context of Primary curriculum.

Are the following two statements correct?
Water at 0 degrees is in the solid state.
Ice at 0 degrees is in the liquid state.

These two statements are \"wrong\". Without further heat loss (freezing) or gain (melting), water & ice will just remain as water & ice at zero deg Celsius. For Primary's curriculum, these questions are meant to test the students' understanding of the process of melting & freezing, & the \"flat\" part of the heating or cooling curve: water starts to freeze or ice starts to melt at zero deg Celsius. For example, if we supply enough heat to a block of ice, it will start to melt (hence part liquid water) at zero deg Celsius. Conversely, if we remove enough heat, water still start to freeze (hence part solid water = ice) at zero deg Celsius. In both instances, we see that both contain part water (liquid) & part ice (solid) until the freezing or melting process is complete, i.e. water & ice can co-exist during its freezing or melting process (freezing or melting point).

In view of the above, does it mean the following two statements are incorrect?
Water at 0 degrees is in the liquid state.
Ice are 0 degrees is in the solid state.

These two statements are correct (unless the statements are further supplemented with phrases such as melting process / freezing process).

Wow! there is so much to water and ice in primary science :roll:

ADoc,
Thanks for the clear explainations. I'm not able to find this kind of explaination in the text book or in the Mini Science encyclopedia. Could you please suggest any book where I can find such explaination for the primary science topics.

anneshirleygilbert,
Where did you get these Qs from?

[ADoc]

tisha:

Wow! there is so much to water and ice in primary science :roll:

ADoc,
Thanks for the clear explainations. I'm not able to find this kind of explaination in the text book or in the Mini Science encyclopedia. Could you please suggest any book where I can find such explaination for the primary science topics.

anneshirleygilbert,
Where did you get these Qs from?

Hi Tisha! Most of the primary texts that I have \"browsed\" so far do not state the term \"co-exist\". Even if they do, they rarely explain further. Not because the books aren't good, just that there isn't a good way to explain to primary students without introducing more scientific terms and concepts. Instead they use the cooling or heating curves to illustrate the boiling and melting processes. What I tell my students is to \"pay attention to the flat part of the curves\" as it contain part solid, part liquid (freezing & melting), & part liquid, part gas (boiling, condensing), as well as what will happen if you remove or add heat at zero & 100 deg celsius. Just when they are about to scratch their heads thinking what the hell you are talking about, I'll bring them a glass of (pure) water with (pure) ice, and a thermometer. All things being equal, the students should be convinced that at zero deg Celsius, we can have part liquid (water) and part solid (ice). It's harder to show with experiment & temperature measurement for part liquid, part gas/steam.

For the more inquisitive students, they may ask what's the temperature of the ice in my home's freezer compartment or can we have liquid water below zero deg celsius? Can solid, liquid, gas/eous (states of water) exist together? Or that at the north pole, is the entire ocean solid ice? That opens a whole new can of very messy worms. haha!

I won't worry too much about explaining concepts other than that required of primary curriculum. You don't need any extra books. Some times, extra books mean extra information, which may end up confusing the kids if we don't spend the effort guiding and explaining clearly. And this upsets certain Ministry, and your kid ends up scoring zero for section B. Oh well...that's really another can of very very messy and frustrating worms.

[anneshirleygilbert]

tisha:

ADoc:

[quote=\"anneshirleygilbert\"]Can somebody pls help with this question?


We know :
The freezing point of water is 0 degrees.
The melting point of ice is 0 degrees.

Are the following two statements correct?
Water at 0 degrees is in the solid state.
Ice at 0 degrees is in the liquid state.

In view of the above, does it mean the following two statements are incorrect?
Water at 0 degrees is in the liquid state.
Ice are 0 degrees is in the solid state.

Thank you in advance.

Hi there! These are great questions! To avoid unnecessary debate from other friendly & knowledgeable forum-ers, let's keep the arguments within the context of Primary curriculum.

Are the following two statements correct?
Water at 0 degrees is in the solid state.
Ice at 0 degrees is in the liquid state.

These two statements are \"wrong\". Without further heat loss (freezing) or gain (melting), water & ice will just remain as water & ice at zero deg Celsius. For Primary's curriculum, these questions are meant to test the students' understanding of the process of melting & freezing, & the \"flat\" part of the heating or cooling curve: water starts to freeze or ice starts to melt at zero deg Celsius. For example, if we supply enough heat to a block of ice, it will start to melt (hence part liquid water) at zero deg Celsius. Conversely, if we remove enough heat, water still start to freeze (hence part solid water = ice) at zero deg Celsius. In both instances, we see that both contain part water (liquid) & part ice (solid) until the freezing or melting process is complete, i.e. water & ice can co-exist during its freezing or melting process (freezing or melting point).

In view of the above, does it mean the following two statements are incorrect?
Water at 0 degrees is in the liquid state.
Ice are 0 degrees is in the solid state.

These two statements are correct (unless the statements are further supplemented with phrases such as melting process / freezing process).

Wow! there is so much to water and ice in primary science :roll:

ADoc,
Thanks for the clear explainations. I'm not able to find this kind of explaination in the text book or in the Mini Science encyclopedia. Could you please suggest any book where I can find such explaination for the primary science topics.

anneshirleygilbert,
Where did you get these Qs from?[/quote]Thank you ADoc, for your explanation. It does clear up our (my daughter and my) understanding. Your explanation actually means all four statements are (or can be) correct when understood in the light of the melting and freezing [u]process. Yes, I understand what you mean by the flat part of the curve on the graph.

Tisha, the question originated from my daughter's mind. I merely put them into words. She's extremely inquisitive and hair-splittingly meticulous when it comes to understanding new concepts, whether science or math or grammar rules.... I guess, you could say she's pretty driven to get full marks for each question.

Thank you, all of you parents and tutors. I've learnt much from this forum. You are all so kind and generous in sharing your knowledge. Many thanks, indeed.