Lower Secondary Science

[Jamesbond]

Dr.Daniel:

usaik:

http://i57.tinypic.com/2dij4np.jpg\">


Hi,

Can someone help me with the question above? What is the answer and why? Thank you so much.

It is D. If you really want to heat a solid powder strongly with a Bunsen burner, the test tube is the way to go. What you want to heat can be surrounded by the Bunsen flame outside the glass. In a flask there is too much extra area of glass that conducts heat away so it is harder to get something as hot. Check out this video. See how the flame surrounds the powder - there's no way you could get it this hot with a big flask.

https://www.youtube.com/watch?v=pnfjXMNBZFo

Hi, can u pl tell me why it can't be B? :nailbite:

[Dr.033430Daniel]

Jamesbond:

Hi, can u pl tell me why it can't be B? :nailbite:

When I look at B, I think of a metal pot with either a metal or glass cover. That's too much surface area to radiate heat. One other thing to think about is that the decomposition of calcium carbonate produces calcium oxide and carbon dioxide gas. If we are decomposing something, we probably want to collect at least one of the products, which you can't do in a covered pot. A test tube you can put a stopper and glass tube in the top to collect the gas for example.

I think the assumption here is that we are doing this in a chemistry lab and not on an industrial scale. I say that because these images are typical chem lab apparatus. But actually B is more often used for cooking food than in a chem lab, although occasionally it may have use in the lab.

[Jamesbond]

Dr.Daniel:

Jamesbond:

Hi, can u pl tell me why it can't be B? :nailbite:

When I look at B, I think of a metal pot with either a metal or glass cover. That's too much surface area to radiate heat. One other thing to think about is that the decomposition of calcium carbonate produces calcium oxide and carbon dioxide gas. If we are decomposing something, we probably want to collect at least one of the products, which you can't do in a covered pot. A test tube you can put a stopper and glass tube in the top to collect the gas for example.

I think the assumption here is that we are doing this in a chemistry lab and not on an industrial scale. I say that because these images are typical chem lab apparatus. But actually B is more often used for cooking food than in a chem lab, although occasionally it may have use in the lab.

:thankyou: :salute:

[Jamesbond]

1)Does rock music make the heart beat faster? What is the hypothesis for this question? :?: :?:


2)what is the best way to keep bacteria from growing in gym shoes?
Name the dependent and independent variable for the test of this question? :?: :?:
:imdrowning: :sad:

[Kate brigid]

Hi , I am looking for science tutor in the east.preferably pasir ris. Any good recommendation will be helpful. Thank you

[adribaby]

Can anyone recommend assessment book for science?

[BayMax_dad]

Hi, Not sure if anyone heard about SmartLab education centre (http://www.smartlab.com.sg)? I am impressed by the large number of students who improved with their tuition program. Wow! Saw that they give full refund if our children do not achieve the desired grade in their final year exam.

[FantasyLandDreams]

BayMax_dad:

Hi, Not sure if anyone heard about SmartLab education centre (http://www.smartlab.com.sg)? I am impressed by the large number of students who improved with their tuition program. Wow! Saw that they give full refund if our children do not achieve the desired grade in their final year exam.

Hmmn...... similar tactic used by Mindchamps for PSLE results....

[BayMax_dad]

Ya, similar to that… But I think theirs are for all levels, even for school exam (not psle, o level etc), they also guarantee the results else full refund too. I think they should be that good to dare to guarantee this. Am checking out more details with them.

[tsh0202]

BayMax_dad:

Ya, similar to that.. But I think theirs are for all levels, even for school exam (not psle, o level etc), they also guarantee the results else full refund too. I think they should be that good to dare to guarantee this. Am checking out more details with them.

Have pm the centre about the reliability of this guarantee.
Asking them if my kid has already attained A and wanted to move further up to A*, will that be possible. They did not reply but just asked me to check their website. So, I have my doubts. They have grouped the percentage of students attaining A and A* together, so the percentage seemed to be high.