Q&A - PSLE Science

[P5G]

kittycat01:

sorry, atutor, the description is not that accurate. it's actually in the psle science paper this year. According to my daughter, the plant is in a sealed beaker of water (no soil) but only the root part is immersed in the sealed beaker. and it's placed under the lamp, not the sun. The rest of the details are correct. Sorry for the confusion. I should have clarified with her first before putting the question down on this forum.


Anyway, just to comment - lots of dd's classmates put CO2 being the answer but others put water.

Hi,

My answer is carbon dioxide as the plant is in a container with limited air. Air only contains 0.03% carbon dioxide. Most of my classmates also choose carbon dioxide as their answer.

[atutor2001]

deleted because information was wrong

[kittycat01]

atutor2001:

kittycat01:

sorry, atutor, the description is not that accurate. it's actually in the psle science paper this year. According to my daughter, the plant is in a sealed beaker of water (no soil) but only the root part is immersed in the sealed beaker. and it's placed under the lamp, not the sun. The rest of the details are correct. Sorry for the confusion. I should have clarified with her first before putting the question down on this forum.


Anyway, just to comment - lots of dd's classmates put CO2 being the answer but others put water.

I may still put \"water\" because there is insufficient water moving through the plant to cool it down (although it is not due to lack of water from the source, but rather it is due to the plant not being able to take in water fast enough to cool it down).

My apology for not being of much help.

I think the answer lies in how the actual question is phrase - then we can have a better interpretation of the requirement.

Thank you, atutor. Just wanted to see what you all think.

[atutor2001]

kittycat01:

atutor2001:

[quote=\"kittycat01\"]sorry, atutor, the description is not that accurate. it's actually in the psle science paper this year. According to my daughter, the plant is in a sealed beaker of water (no soil) but only the root part is immersed in the sealed beaker. and it's placed under the lamp, not the sun. The rest of the details are correct. Sorry for the confusion. I should have clarified with her first before putting the question down on this forum.


Anyway, just to comment - lots of dd's classmates put CO2 being the answer but others put water.

I may still put \"water\" because there is insufficient water moving through the plant to cool it down (although it is not due to lack of water from the source, but rather it is due to the plant not being able to take in water fast enough to cool it down).

My apology for not being of much help.

I think the answer lies in how the actual question is phrase - then we can have a better interpretation of the requirement.

[/quote]Hi kittycat01

My apology again.

The answer is \"carbon dioxide\". I didn't take note of your clarification that it is placed under a lamp and not sun. So the issue of heat is no longer valid.

[Tang]

P5G:

kittycat01:

sorry, atutor, the description is not that accurate. it's actually in the psle science paper this year. According to my daughter, the plant is in a sealed beaker of water (no soil) but only the root part is immersed in the sealed beaker. and it's placed under the lamp, not the sun. The rest of the details are correct. Sorry for the confusion. I should have clarified with her first before putting the question down on this forum.


Anyway, just to comment - lots of dd's classmates put CO2 being the answer but others put water.

Hi,

My answer is carbon dioxide as the plant is in a container with limited air. Air only contains 0.03% carbon dioxide. Most of my classmates also choose carbon dioxide as their answer.

Hi,

I think the correct answer is \"water\" because when carbon dioxide is used up, the plant can replenish it through respiration and photosynthesis can continue until the water in the beaker is depleted.

[atutor2001]

Tang:

Hi,

I think the correct answer is \"water\" because when carbon dioxide is used up, the plant can replenish it through respiration and photosynthesis can continue until the water in the beaker is depleted.

I will agree that the answer is \"water\" if the question is, \"what caused the photosynthesis to finally STOP?\" However, the quesion says the rate of photosynthesis is decreasing.....and is due to what? Since the DECREASE in the rate of photosynthesis is initiated by the lack of CO2, the answer will be CO2. (Plant stores CO2, a process known - carbon sequestration. Therefore, the amount of CO2 released will be less and less. Finally, there is no more CO2 and part of plant will die, leading to decomposition and CO2 is released and the cycle continues)

[kittycat01]

atutor2001:

Tang:

Hi,

I think the correct answer is \"water\" because when carbon dioxide is used up, the plant can replenish it through respiration and photosynthesis can continue until the water in the beaker is depleted.

I will agree that the answer is \"water\" if the question is, \"what caused the photosynthesis to finally STOP?\" However, the quesion says the rate of photosynthesis is decreasing.....and is due to what? Since the DECREASE in the rate of photosynthesis is initiated by the lack of CO2, the answer will be CO2. (Plant stores CO2, a process known - carbon sequestration. Therefore, the amount of CO2 released will be less and less. Finally, there is no more CO2 and part of plant will die, leading to decomposition and CO2 is released and the cycle continues)

Thank you very much, atutor. It's a pleasure reading your explanation. Very detailed and clear.

[Verysuperkiasu]

atutor2001:

Tang:

Hi,

I think the correct answer is \"water\" because when carbon dioxide is used up, the plant can replenish it through respiration and photosynthesis can continue until the water in the beaker is depleted.

I will agree that the answer is \"water\" if the question is, \"what caused the photosynthesis to finally STOP?\" However, the quesion says the rate of photosynthesis is decreasing.....and is due to what? Since the DECREASE in the rate of photosynthesis is initiated by the lack of CO2, the answer will be CO2. (Plant stores CO2, a process known - carbon sequestration. Therefore, the amount of CO2 released will be less and less. Finally, there is no more CO2 and part of plant will die, leading to decomposition and CO2 is released and the cycle continues)

yes, i remember this question - my ds put CO2 as the answer as he also said the issue is decreasing rate of that photosynthesis. And rate of respiration is slower than rate of photosynthesis. I checked with my ds - indeed the question did ask why the rate of photosynthesis is decreasing not stop. wow these days psle question so tricky....

[Tang]

Verysuperkiasu:

atutor2001:

[quote=\"Tang\"]
Hi,

I think the correct answer is \"water\" because when carbon dioxide is used up, the plant can replenish it through respiration and photosynthesis can continue until the water in the beaker is depleted.

I will agree that the answer is \"water\" if the question is, \"what caused the photosynthesis to finally STOP?\" However, the quesion says the rate of photosynthesis is decreasing.....and is due to what? Since the DECREASE in the rate of photosynthesis is initiated by the lack of CO2, the answer will be CO2. (Plant stores CO2, a process known - carbon sequestration. Therefore, the amount of CO2 released will be less and less. Finally, there is no more CO2 and part of plant will die, leading to decomposition and CO2 is released and the cycle continues)

yes, i remember this question - my ds put CO2 as the answer as he also said the same as what atutor said above. I checked with my ds - indeed the question did ask why the rate of photosynthesis is decreasing not stop. wow these days psle question so tricky....[/quote]
I also hope that the answer is CO2, otherwise my sister will lose 2 marks.

During her revision, she was asking me about what are the factors that can be changed to get the same experimental results.
My answer was intensity of light, temperature of water, the number of hydrilla, the type of water plant or amount of CO2 (one of these is already the changed factor for the experiment), but never to put amount of water as the answer because it was a fully submerged plant and the amount of water was not going to factor the results.
So for this question, she just ruled out water, ignoring that the plant is a land plant.

[Verysuperkiasu]

Tang:

I also hope that the answer is CO2, otherwise my sister will lose 2 marks.

During her revision, she was asking me about what are the factors that can be changed to get the same experimental results.
My answer was intensity of light, temperature of water, the number of hydrilla, the type of water plant or amount of CO2 (one of these is already the changed factor for the experiment), but never to put amount of water as the answer because it was a fully submerged plant and the amount of water was not going to factor the results.
So for this question, she just ruled out water, ignoring that the plant is a land plant.

oh..but the sad truth is that we will never know how the moe mark this question, even if we have reasons to support our answer. Because we will not be given the paper back to see or check. What if they decide the answer is water?