Q&A - PSLE Science

[BeContented]

tianzhu:

cwc:

Hi,

This is a P5 exam paper question.

When water boils in a pot, we can see a \"mist\". What is this \"mist\"?
a) Steam
b) Oxygen
c) Water Vapour
d) Water Droplets

Answer given is (d)......can someone kindly help explain? I thot it's (a) :nailbite:

Hi

When water is heated to 100 degrees C, it boils.

During boiling, water changes from a liquid to a hot gas called steam which is invisible.

The white clouds or mist are actually tiny water droplets floating in the air. These are formed when steam loses heat to the surrounding air and changes back into water as it cools. The change of state of steam from gas to a liquid is called condensation.

Best wishes

Arhhhh......now I understand. Thank you

[pixiedust]

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

[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.