Comments on: GCE O-Level 2009 Oct/Nov Combined Science (Physics/Chemistry/Biology) MCQ Paper 1 Suggested Answers & Solutions

By: tan zan hao

tan zan hao — Wed, 23 Dec 2009 15:31:29 +0000

science answer cannot access =(

By: RJ

RJ — Mon, 30 Nov 2009 19:54:07 +0000

hi miss loi , do you have solutions for 2009 'O' level Principle of accounts p1 & p2 ?

By: Little Miss Loi

Little Miss Loi — Tue, 24 Nov 2009 17:05:11 +0000

Hello soon yang from Shenzhen, where I've just joined my sister (who has been shopping like a mad woman at Dongmen). For combined science chemistry qn35, the likely purpose of this question is to test our knowledge of what gas is needed for rusting to occur. While carbon dioxide is indeed soluble in water, do note that this reaction interconverts (i.e. reversible reaction) between CO₂ and H₂CO₃ spontaneously. CO₂ + H₂O ⇌ H₂CO₃ And since we could not determine how much CO₂ has dissolved at any one time, we wouldn't take CO₂ into consideration. P.S. even if we were to consider the scenario where ≤ 20 cm³ of CO₂ is dissolved, there isn't any suitable option (≥ 50 cm³, < 70 cm³) that has been presented to us by the question.

By: lau soon yang

lau soon yang — Fri, 20 Nov 2009 01:26:17 +0000

hey miss loi,
question 35 is the iron fillings in a testube with various gases including carbon dioxide and oxygen.
the question stated,''until no further changes in volume.''
I was taught that carbon dioxide will dissolve in water to form carbonic acid.
So shouldn't we deduct the carbon dioxide' volume?

By: Little Miss Loi

Little Miss Loi — Tue, 17 Nov 2009 08:54:12 +0000

JS: Errr ... if you read the question again it says

A substance was heated in an enclosed space until it became a gas. After the heater was removed, the temperature of the substance was recorded at regular intervals ...

So the scenario was to heat it first to its gaseous state, before being allowed to cool naturally i.e. gas -> condenses into liquid -> liquid -> solidifies into solid -> solid. The graph in the question only captures the cooling process, hence the dropping temperature as time increased.

By: JS

JS — Mon, 16 Nov 2009 23:57:29 +0000

Miss Loi, i have a ques regarding Q9. I thought the questtion says ''until it became a gas'', then how come at the begining it is a gas and not the ending ? cos' you said the gas first changes into a liquid. If the ending is a gas, then why is the answer not C? thanks! (:

By: Wayve

Wayve — Sat, 14 Nov 2009 16:39:45 +0000

hi, can you post de answers for Science Physics and Chemistry Paper 2 and 3 - 2009 O level?
Thanks!

By: Little Miss Loi

Little Miss Loi — Sat, 14 Nov 2009 11:21:55 +0000

GX: OK the Chemistry & Biology Paper 1 solutions are finally up! And I hope jasper will be able to see them now.

By: Mirawr

Mirawr — Sat, 14 Nov 2009 02:56:36 +0000

http://bit.ly/419Gr0 !!!! combined sci mcq answers!!!11

By: Little Miss Loi

Little Miss Loi — Fri, 13 Nov 2009 13:05:12 +0000

Oh thanks Matthewese and Gwen for pointing out Q36, and the answer has been updated.

Yes it should be C as crude oil is first separated into into fractions by fractional distillation. Some of these fractions then undergo a further cracking process to break them down into smaller fractions. This has sometimes been loosely termed as "crude oil cracking" - a term that I errorneously recalled when I did the question