Q&A - PSLE Science

[tianzhu]

ChiefKiasu:

This is a question about atmospheric pressure.

Hi
Talking about atmospheric pressure, I like to share some videos which I chanced upon while surfing.
http://www.videojug.com/film/how-to-suck-an-egg-into-a-bottle
http://www.youtube.com/watch?v=zl657tCCudw
http://www.youtube.com/watch?v=tlQ3qj4eL9s&feature=related

[mathsparks]

Just wondering if anyone knows the answers provided in wendykoh’s/other top schools papers bought in neighbourhood stalls are accurate.


Any idea if the answer keys are from the schools? I seem to find a few that don’t make sense.

[Dharma]

tianzhu:

Dharmaratnam:

Dear ksmama,
The 1st sentence talked about 2 paper bags. The 2nd sentence mentioned that there was a thick plastic bag that was the same size and shape of the paper bag.
The picture however, shows a plastic bag and another with paper bag inside the plastic bag.

Hi, ksmama and Dharma

Thank you for your responses. I’ve done some reading and found that the process when water enters the cells is called osmosis. I remembered reading about it when I was doing my Physical Science in secondary schooldays. So this is just for additional information.
http://www.wisegeek.com/what-are-some-differences-between-plant-and-animal-cells.htm
http://www.purchon.com/biology/osmosis.htm#osmoplant

Going back to the question again, part (b) gives a clue that this question is from the topic Cells in P5.Plant cell has an additional cell wall (fully permeable) as well as a semi-permeable cell membrane. Some books called it selectively permeable. Animal cell has only a cell membrane.
When immersed in pure water, the cell membrane of the animal cell swells up and bursts when it cannot stand the strain anymore. The cell wall of the plant cell is much stronger than the cell membrane and prevents the cell membrane from bursting.

Perhaps, we can compare the plastic bag to that of a cell wall and the paper bag to the cell membrane. Hope this is of some help.

Thanks Tianzhu

[csc]

mathsparks:

Just wondering if anyone knows the answers provided in wendykoh's/other top schools papers bought in neighbourhood stalls are accurate.


Any idea if the answer keys are from the schools? I seem to find a few that don't make sense.

Er... of course the answers are not from the schools... will be an insult to our teachers if they are. Agree that some answers , especially science, are phrased in a really weired way, like how an average student will write them.

My take is that the answers are taken from the student's copy ( the original copy the supplier has used to photocopy from). That explains the way they are written. I think...

[tianzhu]

Thank you for your help.


Q20
Based on the information in the Primary Science textbook, generally fuels consist of wood, coal, oil and natural gas. These fuels come from organisms that are once alive, meaning (c) is correct. I am wondering if nuclear energy is considered as fuel, meaning (c) is not true.

Q21
Statement (3) ---Is it correct?

http://farm4.static.flickr.com/3649/3478546706_793cfc54f9_o.jpg\">

[mathsparks]

Thks csc for yr response. Those sellers are unscrupulous for leading a lot of parents/students into believing that those ridiculous answers are the right ones.


Haiz. Not sure now where to turn to for Science resources.

[ksmama]

tianzhu:

Thank you for your help.


Q20
Based on the information in the Primary Science textbook, generally fuels consist of wood, coal, oil and natural gas. These fuels come from organisms that are once alive, meaning (c) is correct. I am wondering if nuclear energy is considered as fuel, meaning (c) is not true.

Q21
Statement (3) ---Is it correct?

http://farm4.static.flickr.com/3649/3478546706_793cfc54f9_o.jpg\">

Hi, based on dictionary, fuel also includes any fissile material that is used to release energy by nuclear fission in a nuclear reactor. Since nuclear energy's source is from radioactive uranium metal, it means not all fuel are derived from living organism

I have always thought solar energy means light and heat energy from the sun...

[tianzhu]

ksmama:

I have always thought solar energy means light and heat energy from the sun...

Hi
You are right. I missed out heat energy from the Sun.
A useful link to learn more about solar energy. http://www.eia.doe.gov/kids/energyfacts/sources/renewable/solar.html

[tianzhu]

Hi Dharma


Going back to that roller coaster's question again , here's a weblink about the conversion of energy in a ride.
http://www.hk-phy.org/oceanpark/rol/resource/rollercoaster_e8.swf

Enjoy the thrills.But I've to miss it, my old heart may not be able to take the excitement.

Have fun.

[tianzhu]

Thank you for your help.Any alternative phrases for the answers?



http://farm4.static.flickr.com/3400/3506857174_ae0eb725a0_o.jpg\">

The answers as in WS
http://farm4.static.flickr.com/3543/3506049065_2d913ee008_o.jpg\">