Q&A - PSLE Science

[elkniwt]

Fat Mama:

Hi,

Ans (2) is correct.

Reason being marbles are round and hv gaps bet them. When liquid is pour in, it will fill up the gaps of the marbles. So vol of gas should be more than 700 which is (2) 750

Hi Fat Mama,

Thanks for taking time to reply

When the question says the total volume of marbles is 100 cm3, we thought it meant the total volume of the marbles without the gaps. :? (Cos usually, if we say volume of 1 marble is 10 cm3, volume of 10 marbles will be 100cm3, we don't factor in the gaps right?? )

[Robertpattinsonidle]

elkniwt:

Fat Mama:

Hi,

Ans (2) is correct.

Reason being marbles are round and hv gaps bet them. When liquid is pour in, it will fill up the gaps of the marbles. So vol of gas should be more than 700 which is (2) 750

Hi Fat Mama,

Thanks for taking time to reply

When the question says the total volume of marbles is 100 cm3, we thought it meant the total volume of the marbles without the gaps. :? (Cos usually, if we say volume of 1 marble is 10 cm3, volume of 10 marbles will be 100cm3, we don't factor in the gaps right?? )

this is becos the pebbles dont have definite shape. If we fill a bucket with 10 pebbles or stones, there are still air spaces cuz pebbles cant be compressed and have definit shape

[Alarmchain]

Total Vol in Bottle = 1000cc


Substances that cannot be compressed that are added:
a) Marbles, Vol = 100cc
b) Substance B, Vol = 200cc
Therefore, total volume occupied by substances that cannot be compressed = 300cc

From here, total available space in bottle becomes 1000cc - 300cc = 700cc

Substance D is compressible.
Original Vol of D = 700cc
Added vol of D = 100cc
Total Vol of D = 800cc

Despite D having a total vol of 800cc, the available space in bottle is still 700cc. So, substance D must compress itself to fit into the available 700cc volume. Hence, I think 700cc is the correct answer.

[Fat Mama]

elkniwt:

Fat Mama:

Hi,

Ans (2) is correct.

Reason being marbles are round and hv gaps bet them. When liquid is pour in, it will fill up the gaps of the marbles. So vol of gas should be more than 700 which is (2) 750

Hi Fat Mama,

Thanks for taking time to reply

When the question says the total volume of marbles is 100 cm3, we thought it meant the total volume of the marbles without the gaps. :? (Cos usually, if we say volume of 1 marble is 10 cm3, volume of 10 marbles will be 100cm3, we don't factor in the gaps right?? )

Hi,

Check with DD this morning and she explained to me that 700 shd be the correct ans.

Our DDs are right.

Sorry for initial wrong explanation. :oops: :oops:

[charsen]

elkniwt:

Hi,


Need help on this qn from CHS prelim :

http://i46.tinypic.com/1zp03fb.jpg\">

Answer in answer key is (2). dd's ans is (1) ?? (I think ans key is wrong, need some advices. Thanks!) :?:

Hi
Volume of substance b + marbles---->300cm3
Since Substance d can compress,the volume of the substance d should be 700cm3.
cheers

[Robertpattinsonidle]

charsen:

elkniwt:

Hi,


Need help on this qn from CHS prelim :

http://i46.tinypic.com/1zp03fb.jpg\">

Answer in answer key is (2). dd's ans is (1) ?? (I think ans key is wrong, need some advices. Thanks!) :?:

Hi
Volume of substance b + marbles---->300cm3
Since Substance d can compress,the volume of the substance d should be 700cm3.
cheers

i dont understand the reason behind this. anyone can explain pls?

[elkniwt]

Dear Fat Mama, charsen and Alarmchain,


Thank you so much for your confirmation!! :hugs:

Dear Robertpattinsonidle,

You can take note of the explanations given by Fat Mama, charsen and Alarmchain.

[charsen]

Robertpattinsonidle:

charsen:

[quote=\"elkniwt\"]Hi,


Need help on this qn from CHS prelim :

http://i46.tinypic.com/1zp03fb.jpg\">

Answer in answer key is (2). dd's ans is (1) ?? (I think ans key is wrong, need some advices. Thanks!) :?:

Hi
Volume of substance b + marbles---->300cm3
Since Substance d can compress,the volume of the substance d should be 700cm3.
cheers

i dont understand the reason behind this. anyone can explain pls?[/quote]Hi
Substance B and the marbles have a definite volume.thus,they could not be compressed.Hence,their volume will be always 300cm3.Substance d can be compressed.For example,assume that substance d is air.If there is 700cm3 of air in the bottle and 300cm3 of other substances which has a definte volume,no matter how much volume of air is pumped in the bottle,assuming that the capacity of the bottle is 1litre,the volume of air remains the same as air occupies space.Relate this explantion to the question and you should be able to answer your doubts on the question.

Remember,althogh air can be compressed,it cannot be compressed fully.
Cheers

[charsen]

Robertpattinsonidle:

charsen:

[quote=\"elkniwt\"]Hi,


Need help on this qn from CHS prelim :

http://i46.tinypic.com/1zp03fb.jpg\">

Answer in answer key is (2). dd's ans is (1) ?? (I think ans key is wrong, need some advices. Thanks!) :?:

Hi
Volume of substance b + marbles---->300cm3
Since Substance d can compress,the volume of the substance d should be 700cm3.
cheers

i dont understand the reason behind this. anyone can explain pls?[/quote]Hi
Substance B and the marbles have a definite volume.thus,they could not be compressed.Hence,their volume will be always 300cm3.Substance d can be compressed.For example,assume that substance d is air.If there is 700cm3 of air in the bottle and 300cm3 of other substances which has a definte volume,no matter how much volume of air is pumped in the bottle,assuming that the capacity of the bottle is 1litre,the volume of air remains the same as air occupies space.Relate this explantion to the question and you should be able to answer your doubts on the question.

Remember,althogh air can be compressed,it cannot be compressed fully.
Cheers

[G Tan]

Can someone teach me how to upload a picture to my post