Q&A - PSLE Science

[mother777]

Nebbermind:

starlight1968sg:

What? add bleach and duckweed will grow better ??? :yikes:

out of curiosity I search and found that there r experiment on how 'sterilized' duckweed will affect its growth/production. but is this topic covered in pr sch syllabus?

Hi Nebbermind,

I agree, was baffled when read this question. When i googled, got sites telling how to grow duckweed and affect of bleach on it.

Bleach in minute amount (small amounts) is used to kill the bacteria and organisms affecting duckweek growth. The duckweek is supposed to be rinsed in bleach for 10~30 seconds to kill the micro-organisms. This will allow unhindered growth of the duckweed.
But if you rinse it for long time, the duckweed itself will be bleached and die.

So I am confused here too...

[mother777]

Nebbermind:

starlight1968sg:

What? add bleach and duckweed will grow better ??? :yikes:

out of curiosity I search and found that there r experiment on how 'sterilized' duckweed will affect its growth/production. but is this topic covered in pr sch syllabus?

Hi Nebbermind,

I agree, was baffled when read this question. When i googled, got sites telling how to grow duckweed and affect of bleach on it.

Bleach in minute amount (small amounts) is used to kill the bacteria and organisms affecting duckweek growth. The duckweek is supposed to be rinsed in bleach for 10~30 seconds to kill the micro-organisms. This will allow unhindered growth of the duckweed.
But if you rinse it for long time, the duckweed itself will be bleached and die.

So I am confused here too...

[hashroop]

hashroop:

Hi, pls help. For a developing human foetus, which system(in correct order) develops first.

Circulatory, muscular, skeletal,digestive, respiratory?

Thanks

resending...thx

[Nebbermind]

i think the circulatory gwah. That wld be the main mean to transfer nutrients from mom to foetus for it to build the rest.

[hashroop]

Nebbermind:

i think the circulatory gwah. That wld be the main mean to transfer nutrients from mom to foetus for it to build the rest.

thank you, but Im not too sure of the right order.Sometimes I think its the skeletal that should come first to support the growing foetus.Im just lost :? Im waiting for the centre to release the papers to see what is the correct answer. Once received I'll definitely post up here for sharing purpose

rgds

[benleetube]

hashroop:

Nebbermind:

i think the circulatory gwah. That wld be the main mean to transfer nutrients from mom to foetus for it to build the rest.

thank you, but Im not too sure of the right order.Sometimes I think its the skeletal that should come first to support the growing foetus.Im just lost :? Im waiting for the centre to release the papers to see what is the correct answer. Once received I'll definitely post up here for sharing purpose

rgds

Hi,
I think this website may help:
http://in.answers.yahoo.com/question/index?qid=20100922035844AAHry4J

[benleetube]

Hi, I just wanted to ask this question out of curiosity. How is natural wind formed? And by natural, I mean it is not created by fans, etc.


Thanks.

[atutor2001]

Kloggy:

Hi, can someone help with the following:


An experiment was carried out by placing duckweeds in two beakers with 500ml of water each. 10 ml of bleach was added to one of the beakers. Write an hypothesis for the experiment.

The answer provided was that the duckweed will grow better in the water with bleach added. But why ?

Thanks.

A hypothesis is effectively \"a prediction of the outcome of an experiment\". A hypothesis is supposed to help us in formulating the experimental steps.

Therefore, it is ok for the hypothesis to be proven wrong after the experiment - after all, it is just a guess.

For the above question, the chosen hypothesis must be one that can be verified (i.e. proven right or wrong) by the experimental steps given.

[tianzhu]

benleetube:

Hi, I just wanted to ask this question out of curiosity. How is natural wind formed? And by natural, I mean it is not created by fans, etc.


Thanks.

Hi

Hope this helps.

http://itehome.apogee.net/kids/?ver=kkblue&utilid=itehome&id=16208

Best wishes

[tianzhu]

Kloggy:

Hi, can someone help with the following:


An experiment was carried out by placing duckweeds in two beakers with 500ml of water each. 10 ml of bleach was added to one of the beakers. Write an hypothesis for the experiment.

The answer provided was that the duckweed will grow better in the water with bleach added. But why ?

Thanks.

Hi

In answering this question, a student needs to have a good understanding of “What is a hypothesis?”

He or she needs not venture too far; a good explanation is given in PSLE Science Guide (MC).

A hypothesis is an educated guess; it is what you predict the results of an experiment will be.

A hypothesis may or may not be correct.

For more reading, you may refer to this link.
http://primary-school.helium.com/how-to/9563-how-to-write-a-hypothesis

Judging from the information you have provided, I guess that the person carrying out the experiment wants to find out if duckweeds grow well in water containing bleach.

How does the amount of bleach added to water (independent variable) affect the growth of duckweeds (dependant variable)?

I’d go for

a)If the amount of bleach added to water is increased, then the duckweeds will grow faster. or b) The amount of bleach added to water affects how well the duckweeds grow.

Best wishes