Q&A - PSLE Science

[Verysuperkiasu]

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

Ans is (3). Need to know why?

Dd has no prob with answer options A, B and D. Vol of B=15, Vol of C=20 but for (C) - how to find if vol of object A is bigger than vol of C.....

[isetan]

Hi, my dd has a question from school teacher:


1) a battery serving 2 bulbs in series in a circuit;
2) a battery serving 3 bulbs in parallel in a circuit.

Which bulb/circuit of the above is brighter?

[tianzhu]

isetan:

Hi, my dd has a question from school teacher:


1) a battery serving 2 bulbs in series in a circuit;
2) a battery serving 3 bulbs in parallel in a circuit.

Which bulb/circuit of the above is brighter?

Hi

I think students are taught in schools about bulbs connected in series and parallel.

When more bulbs are connected in series, the individual bulbs in the circuit shine less brightly because the electric current passing through them is reduced.

When more bulbs are connected in parallel, the individual bulbs in the circuit shine as brightly as before. The electric current passing through the bulbs stays the same.

Hence, the bulbs in (2) are brighter.

Best wishes

[fightingmom]

isetan:

Hi, my dd has a question from school teacher:


1) a battery serving 2 bulbs in series in a circuit;
2) a battery serving 3 bulbs in parallel in a circuit.

Which bulb/circuit of the above is brighter?

Hi isetan,

Hope the below explanation helps:

Assume the battery is 1.5V

For (1), the battery voltage is reduced since the 2 bulbs arranged in series are \"sharing\" the 1.5V . Thus, each bulb only has 0.75V of brightness

For (2), the battery voltage is not shared since the 3 bulbs are arranged in parallel. Thus, each bulb has 1.5V of brightness.

Therefore, answer is (2)

[isetan]

Hi Tian Zhu, Fighting mom,


Well explained. Thanks!

[Verysuperkiasu]

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[fightingmom]

isetan:

Hi Tian Zhu, Fighting mom,


Well explained. Thanks!

You are welcome! I am learning too

[Verysuperkiasu]

I know that dry ice sublimes (from solid straight to gaseous without going thru liquid state). But the appearance of the mist - doesn’t it suggest that it is in the liquid state? because anything that u can see like clouds, mist, fog are not in gaseous state but they are actually water droplets (liquid state) right?

[ADoc]

Verysuperkiasu:

I know that dry ice sublimes (from solid straight to gaseous without going thru liquid state). But the appearance of the mist - doesn't it suggest that it is in the liquid state? because anything that u can see like clouds, mist, fog are not in gaseous state but they are actually water droplets (liquid state) right?

Hi there! A quick explanation would be:
The white mist/smoke/fog is in fact condensed water vapour from the surrounding air.

Perhaps a useful way to make yout kid understand without having to explain sublimation process would be:

(1) dry ice is solidified carbon dioxide

(2) it is very cold

(3) when dry ice sublimes, the carbon dioxide vapour (gaseous) is also very cold

(4) the surrounding water vapour in the air (which is at a higher temperature) loses heat to the carbon dioxide vapour since heat flows from regions of higher temperature to regions of lower temperature

(5) water vapour cools and condenses to form the white mist/cloud that we see when dry ice sublimes

Of cos the mechanics is a little more complicated than above explanation, but these should be sufficient to \"cure\" our kids' curiosity and \"why why why\"...

hope this is useful. cheers!

[Michaelia0816]

Hello!

I do not know how to explain but I do understand, but can you give me the answer, it is based on the Science Process Skill Interaction P5-6 WS 11, Q2, Q4 and Q5!

2)before the sandine is canned, it is heated to a high temperature. Explain how this process helps prevent the sandine from decomposition.



4) Wei Song wants to investigate the changes dead matter goes through during the decomposition process. He makes obversations after 5 days.
He has the following apparatus and materials:
A conical flask with a rubber stopper, A test tube containing limewater, A delivery tube and A dead fish.
What changes do you expect Wei Song to observe regarding:
a) The appearance of the fish:
b) The texture of the fish:__
c) The appearance of the limewater:

5) What can Wei Song conclude from the results of his experiment?
___