Q&A - PSLE Science

[tianzhu]

[quote]MCQ Q30 - Option (3) of the same paper. I don't understand option 3 that \"Carbon dioxide is not returned to leaves\" is correct in concept.[/quote]
Hi VC

The question asks a student to identify which of them is wrong.

Focus on the respiratory system in plants; you may refer to PSLE Science Guide (MC)

Plants respire all the time, day and night. Carbon dioxide is released and oxygen is taken in during respiration.This explains why \"Carbon dioxide is not returned to leaves\" is correct in concept.

Do not get it mixed up with photosynthesis.

Best wishes

[tianzhu]

Hi VC


Steam is hot water vapour at boiling point(100 degree Centigrade).
It condenses when it meet a cooler/colder surface.

I think students are more familiar with experiment involving holding a glass plate or copper sheet near a kettle spout.

In the beginning, one can see many water droplets on the surface of the glass plate or copper sheet as the hot steam condenses to form water droplets when it touches the cooler surface of the glass plate or copper sheet.

After some time, condensation cannot take place as the glass plate or copper sheet has become hotter.

Applying the same concept, in the beginning steam condenses to form white clouds as it touches the cooler surrounding air near the kettle spout.

After some time, the surrounding air near the spout gets hotter, so no condensation takes place. For condensation to take place again, the steam has to move further away to come into contact with the cooler surrounding air which is further away from the spout. This explains why the cloud moves higher and higher.

Best wishes

[Tang]

Vanilla Cake:

Compare the following differences between the respiratory and circulatory system in plants and in human beings. Which of them is wrong?


Option 1
Plant: Exchange of gases takes place in the leaves
Human: Exchange of gases takes place in the lungs

Option 2
Plant: Oxygen is pumped to all parts of the plant
Human: Oxygen is pumped to all parts of the body

Option 3
Plant: Carbon dioxide is not returned to leaves
Human: Carbon dioxide is returned to the lungs.

Option 4
Plant: There is no blood to carry food around the plant
Human: Blood carries food around the body

Answer given is option (2).
Is this correct?
Option (1) and option (4) are obviously correct.
Pls help to explain why option (2) is chosen instead of option (3) for this question.
TIA for your time and effort.

Hi,

I personally think option (3) is the correct answer.


Respiration is the conversion of food to energy. For this process to take place, oxygen is used up and carbon dioxide is produced.


Exchange of gases takes place at the leaves through stomata. So oxygen needs to be pump from the leaves to all parts of the plant and carbon dioxide to the leaves to be removed. The former shows that option (2) is correct while the latter shows that option (3) is wrong, hence the correct answer - option (3).

[janet88]

Hi Parents,

I happened to see this 'Science PSLE Revision & Examination Papers (2E)…is it worth while getting ? TIA

This thread is really interesting and explainations are clear. Thanks.
I’ve been reading up P5 Science to get a feel and don’t quite understand…now I do.

[kenobi]

Vanilla Cake:

Compare the following differences between the respiratory and circulatory system in plants and in human beings. Which of them is wrong?


Option 1
Plant: Exchange of gases takes place in the leaves
Human: Exchange of gases takes place in the lungs

Option 2
Plant: Oxygen is pumped to all parts of the plant
Human: Oxygen is pumped to all parts of the body

Option 3
Plant: Carbon dioxide is not returned to leaves
Human: Carbon dioxide is returned to the lungs.

Option 4
Plant: There is no blood to carry food around the plant
Human: Blood carries food around the body

Answer given is option (2).
Is this correct?
Option (1) and option (4) are obviously correct.
Pls help to explain why option (2) is chosen instead of option (3) for this question.
TIA for your time and effort.

If this is Primary Science, I'd say it's option 2.

Transport system in plants involve only water and food, so the phrase \"returned to leaves\" is not appropriate. All parts of plants carry out respiration, hence it's not solely \"returned to leaves\".

Again, transport system in plants do not involve transport of oxygen. Similarly, all parts of plants carry out respiration, so they do not draw their oxygen from leaves.

[Vanilla Cake]

Hi Uncle tianzhu, starlight1968sg and ParentingChildren,


Thks for your helpful replies. I have copied and pasted your comments on Excel spreadsheet and print it for my younger sister to learn, study and understand the concept behind this question.

Tang:

I personally think option (3) is the correct answer.

Respiration is the conversion of food to energy. For this process to take place, oxygen is used up and carbon dioxide is produced.

Exchange of gases takes place at the leaves through stomata. So oxygen needs to be pump from the leaves to all parts of the plant and carbon dioxide to the leaves to be removed. The former shows that option (2) is correct while the latter shows that option (3) is wrong, hence the correct answer - option (3).

Hi Tang,

Thks for your reply as my option is also (3) but the answer given is option (2).

janet_lee88:

I happened to see this 'Science PSLE Revision & Examination Papers (2E)...is it worth while getting ?

Does the front cover have an eagle?

[janet88]

Hi Vanilla Cake,

Yes, the one with the eagle on the front cover.

http://postimage.org/image/3ftrlipw/

[Vanilla Cake]

janet_lee88:

Hi Vanilla Cake,

Yes, the one with the eagle on the front cover.

http://postimage.org/image/3ftrlipw/

Hi janet_lee88,
I have PM for you.

Thks.

[youngtay]

Mr Tianzhu


Thanks

[atutor2001]

kenobi:

Transport system in plants involve only water and food, so the phrase \"returned to leaves\" is not appropriate. All parts of plants carry out respiration, hence it's not solely \"returned to leaves\".

Again, transport system in plants do not involve transport of oxygen. Similarly, all parts of plants carry out respiration, so they do not draw their oxygen from leaves.

Hi Kenobi

You have given the best explanation. Unfortunately, many Pr school kids think that respiration (like photosynthesis) is carried out by the leaves only.

Regards