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Hi I’m confused on this question. The answer given is:

oxygen: unchanged

carbon dioxide: decreased

In my understanding, both oxygen and carbon dioxide should be unchanged as this is a toy. Anyone has any suggestions? Thanks in advance! 




(1) I’m with you on the toy hamster point. (A pet hamster in a sealed tank will be a cruel and bad idea for a question. A cockroach instead perhaps?). 

(2) CO2 dissolves in water slowly (stale water is more acidic). If that’s a good datalogger then it will show [CO2]. O2 won’t dissolve as much in one day and it won’t show on datalogger.

(3) Depending on the food, bacteria and fungi might break it down to a certain degree in 24 hours, via aerobic respiration in this case most likely. Looks like the answer chose not to consider this factor. 

To a P6 kid, I might stress on point (1) and point (2), and put very little weight on point (3).

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Thanks Cogito for your detailed explanation. 

So based on your words, if we consider all 3 points, both oxygen and carbon-dioxide will decrease. If we only consider your points (1) and (2), then it fits the given answer (oxygen unchanged and carbon-dioxide decreased).

The question here is how do we know which points to be considered? I am not sure if point (2), ie, “carbon-dioxide is dissolves in water” is in the P5 Science syllabus? 

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Short answer: I don’t know what the correct answer should be.

Long answer: There are science questions, where there is a different correct answer at every level/depth of consideration. Some of these will simply start endless debates. I usually would advise my son to take the learning points from the question and move on. This question seems to me to qualify for that category.


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Thanks Cogito for the wise suggestion! Really appreciate it!

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