Q&A - PSLE Science

[BeContented]

pixiedust:

cwc, tianzhu's answer is bang-on. This is one of the misconception explained in ACE science explorer booklets recommended by janet.

Hmm....then time to get THE BOOKLETS Now got reason to go Popular and use the 20% NTUC card liao. :lol:

[kitty2]

pixiedust:

cwc, tianzhu's answer is bang-on. This is one of the misconception explained in ACE science explorer booklets recommended by janet.

May i know where to get the ACE science explorer booklets ?

Thanks

[Eddow]

Need help on this.. Qn 19 of MCQ.

http://www.orlesson.org/orp/10Sc/2010-P5-Sc-SA1-HenryPark.pdf

Kindly help to explain the answer.
Thanks lotx..^_^

[tianzhu]

Eddow:

Need help on this.. Qn 19 of MCQ.

http://www.orlesson.org/orp/10Sc/2010-P5-Sc-SA1-HenryPark.pdf

Kindly help to explain the answer.
Thanks lotx..^_^

Hi

The young plants (triangular shape) are found along the shorelines of the river, thus likely to be dispersed by water and have fibrous husks.

As for the other type of young plants, take note that some of them grow behind the parent plant and some of them are found in line with the parent plant, hence ruling out wind dispersal. For those young plants growing on the opposite bank of the river, one possibility is that they are dispersed by animals swimming or flying across the river. Therefore, they may have hook like structures that hook to the furs of animals and are dispersed when they shake their bodies.

Hence (1) is a logical answer.

Best wishes

[Niedino]

Eddow:

Need help on this.. Qn 19 of MCQ.

http://www.orlesson.org/orp/10Sc/2010-P5-Sc-SA1-HenryPark.pdf

Kindly help to explain the answer.
Thanks lotx..^_^

Hi Eddow,

Tianzhu is right. I'll offer up another alternative explanation, utilising the process skill of analysis. You may explain to your child that the triangular plants are situated around the river. So that means it disperses by water therefore needing a fibrous husk. Most children at this stage will put option (1) and (3). Teach your child to eliminate option 2 & 4. After that, explain that the lotus shaped trees grow against the wind direction, hence it cannot be by wind disperal. Eliminate option (3), leaving option 1, hooks (dispersal by animals) as the only answer. By crossing out the options, your child should find it easier to check his or her work later after the test.

Hope it helps.

[Eddow]

Thanks tianzhu & Niedino for the detailed explaination. Have show it to DS1, he’s able to understand it. ^_^

[concerned9999]

hi, i need help on this question on how to explain it. I know why but i dont know how to explain it…


When a glass of water is put into a freezer and is taken out from the freezer after a few hours, the glass is observed to be cracked. why does the glass crack?

[xznat]

The anomalous expansion of water as it freezes. Ice has a crystalline structure which leaves relatively (as compared to water) large spaces in between H20 molecules. Thus when the molecules rearrange themselves they take up more space (ie occupy a larger volume), hence creating an outward force on the glass.

[carebear]

concerned9999:

hi, i need help on this question on how to explain it. I know why but i dont know how to explain it...


When a glass of water is put into a freezer and is taken out from the freezer after a few hours, the glass is observed to be cracked. why does the glass crack?

Water contracts when it is cooled, like most solids.
However when it reaches 4deg C it start to expand rather than contract. It will expand further as it reaches its freezing point.
Glass however contracts as it is cooled.
So if the ice expands and the glass contract, the ice will break the glass.

[concerned9999]

thanks xznat and carebear for the explanation now i know how to explain in exams