Q&A - PSLE Science

[WS1234567]

youngtay:

Please help.



http://www.orlesson.org/orp/09Sc/2009-Sc-SA2-Nanyang.pdf

question 22, the worksheet answer is 3, my dd's answer is 2, and for
question 29, the worksheet answer is 3, my dd's answer is 1, can help to confirm which is correct?

TIA

For Q22,
option 1 is wrong because the driection of the batteries are not the same.
option 2 is right. the change in the position of the switch did not change the actual setup.
option 3 is wrong because the two sets of batteries used to be in parallel but now they are in series.
option 4 is wrong because now the bulbs are placed in parallel and not in series.

I think the worksheet answer could have a typo error.

For Q 29,
Answer should be 3.
IN change C, notice that the poles of the batteries cancel each other out leaving the circuit to have the actual effectiveness of 2 batteries, ie. same as before.
All other changes did make the bulbs brighter.

[youngtay]

Mr Tianzhu and WS1234567


Tks for your help.

Best wishes

[kancheongmum]

naggo-nitemare:

Ler:

[quote=\"tianzhu\"]
Hi everyone. V paiseh for error.
Q15 - explanation should be \"Anther is shorter than stigma\" to prevent SELF pollination.

Tks

[/quote]Hi nago-nitemare
Q15) I have check with DS school science teacher ans should be option (4).
A- flower is beautiful means petals colourful and bright to attract insects
B- nectar sweet attract insects
C - this adaptation does not help
D - Stigma is hanging out of the flower this adaptation helps because insects may land there because of the nectar

for Q21, options (1) (2) and (3) I would say are all correct. Looking at circuit again, actually we just need to close S1 and it will already be a closed circuit for the bell to ring. The other switches will not affect the bell.

[tianzhu]

Hi kancheongmum


For Q21, if S2 is closed, you will get a short circuit.

If I can remember correctly, only closed/complete circuit and open circuit are mentioned in the old i- science P5 textbook/PSLE Science Guide (MC).You may wish to confirm if short circuit is mentioned in the new books.

For PSLE science, I think it is good enough to know that a short circuit offers an easier path for current to flow through. This means a large amount of current goes through the wire, with very little current going through any of the other circuits in parallel with the short-circuited wire. Therefore the buzzer and light bulb will not work.

https://docs.google.com/fileview?id=0B1RM96g5JaKuZTA4MjRlYzktNWJiNC00ODIxLWJkMmQtY2YzYzljOGY0NmJk&hl=en&authkey=CK70iZMF
Please go to page 107 to read Q21.

You may find out more about short circuit from this link.
http://www.energyquest.ca.gov/projects/open-short-circuit.html

The answer is (2).

Best wishes

[tianzhu]

kancheongmum:

Q15) I have check with DS school science teacher ans should be option (4).

A- flower is beautiful means petals colourful and bright to attract insects
B- nectar sweet attract insects
C - this adaptation does not help
D - Stigma is hanging out of the flower this adaptation helps because insects may land there because of the nectar

Hi kancheongmum

I think the keywords in this question are adaptations to ensure it is pollinated by animals.

Please go to pg 104 to read Q15.
https://docs.google.com/fileview?id=0B1RM96g5JaKuZTA4MjRlYzktNWJiNC00ODIxLWJkMmQtY2YzYzljOGY0NmJk&hl=en&authkey=CK70iZMF

In PSLE science, students learned that flowers pollinated by animals are usually large, brightly coloured and scented. The anthers do not hang out of the flowers. Stigmas are sticky to catch pollen grains.Please refer to PSLE Science Guide(MC).

For (D), stigma is hanging out of the flower is definitely not a characteristics of an animal pollinated flower. It is needed for wind pollinated flower to catch pollen grains floating in the air.

Whether a beautiful flower means the petals are colourful and bright to attract insects is highly debatable. Birds and insects select flowers not only by smell but also by colour.

Beautiful is a very general term, a wind pollinated flower may be as beautiful as an animal pollinated one.

With D out, option (3) and (4) are offside.

Between option (1) and (2) , I am more inclined to go for (2).

Best wishes

[kancheongmum]

Hi Tianzhu


Really learn something new and this is how current travel. Million thanks.
Now it make sense to me why batteries arrange in parallel has the strength of one battery.

[tianzhu]

kancheongmum:

Hi Tianzhu


Really learn something new and this is how current travel. Million thanks.
Now it make sense to me why batteries arrange in parallel has the strength of one battery.

Hi

You're welcome.

Best wishes

[youngtay]

hi, Please help



P5 Science from Nanhua SA2 2009

question 4. Nancy prepared a glass container which contained 100 cm3 of air (taken from the surroundings) as shown in the set-up shown below.
(Sorry there is a picture ,but I don’t know how to add link,there is a rubber stopper on top of the glass container)

What is the approximate volume of oxygen present in the container?
(1) 1 cm3
(2) 21 cm3
(3) 78 cm3
(4) 100 cm3

question 16. Which of the following statements about the animal and plant transport systems are true?

A. An animal needs an organ to pump blood to transport materials around the body.
B. No organs are needed by a plant to transport materials around the plant.
C.A plant has only one type of tube to transport materials around the plant.
D.Only oxygen and digested food are transported around the body of an animal.

(1) A only
(2) A and B only
(3) A,B and D only
(4) B, C and D only.


question 28. Tom found 3 objects and wanted to test if they were magnets. He bought a magnet from the school bookshop and placed it next to each of the objects. This is what he observed.

Object A – No reaction
Object B – Repelled
Obejct C – Attracted

Which of the following object (s) is definitely a magnet?

(1) Object B
(2) Object C
(3) Objects A and C
(4) Objects B and C


question 29. Alex conducted a study on animal X and Animal Y. He used a checklist and placed a tick in the appropriate box when he made an observation. The completed checklist is as follows:



Observation Animal X Animal Y

Eggs are laid in water Y Y
There are 4 stages in the life cycle
It has six legs Y


Which of the following could be Animals X and Y?

Animal X Animal Y

1. frog mosquito
2. frog dragonfly
3. mosquito frog
4. dragonfly frog


Please help. TIA

[tianzhu]

Hi youngtay


Please go to page 3,10,15 and 16 of this link to read the questions.
http://www.orlesson.org/orp/09Sc/2009-Sc-SA2-NanHua.pdf

For Q4, in primary science, students learned that air is a mixture of nitrogen, oxygen, carbon dioxide, water vapour and other gases. These gases are present in the air in different amounts.

For a volume of 100ml of air, it’ll have 21ml of oxygen or 21%.
Therefore, the answer is option (2)

For Q16, under the topic on transport system in plants, a student learned that a plant has two kinds of tubes; they are Xylem tubes (water and minerals) and Phloem tubes (food).

In Circulatory System, students learned that besides oxygen and digested food, the blood also transports water, carbon dioxide, nutrients and other waste materials.

Therefore option (C) and (D) are offside.

The heart pumps blood around the body and no organs are needed by plants to transport materials around the plant.

The answer is option (2)

Under the topic on magnets, a primary student learned about magnetic and non magnetic materials. They also learned that magnets can attract or repel one another, like poles repel and unlike poles attract.

Object A is a non magnetic material.
Object B is a magnet. The repulsion is due to unlike poles facing one another.
Object C is a magnetic material. We cannot conclude that it is a magnet unless we carry out the repulsion test.

Therefore, the answer is option (1)

For Q29, I’ll assume that you have knowledge on where the animals lay their eggs or the number of legs they have from reading your books.

Observe the row on life cycle in the observation list, there are no ticks. This means both X and Y do not have four stages in their life cycles.

The dragonfly and frog have three stages in their life cycle, while the mosquito has four.

Therefore, the answer is option (2).

Best wishes

[youngtay]

Mr Tianzhu


Thanks for your explanation.

Best wishes