Physics, Chemistry and Biology: Post your doubts here!

[Sijal Mirza]

can u please tell me what topics from physics come in the ATP paper? (O-level) like in chemistry its mainly just Acids, Bases n Salts , Rate of reaction and Moles..
PLEASE HELP!

 

[Princess Raven]

they absorb more heat energy from the hot water

hey i have a question in chemistry.. do u know y copper cannot react with a dilute acid to form a salt?? i mean y do we have to change it to copperoxide or copperchloride?? plz reply ASAP

 

[CaveDweller65]

hey i have a question in chemistry.. do u know y copper cannot react with a dilute acid to form a salt?? i mean y do we have to change it to copperoxide or copperchloride?? plz reply ASAP

Copper is quite low in the reactivity series
It's oxide or chloride is perhaps more reactive!

 

[Princess Raven]

Copper is quite low in the reactivity series

So its not just gonna be copper then right... i mean if they say silver or platnium the same rule applies?? and what if they are really high in the reactivity series? would we be able to make a salt?

 

[Princess Raven]

Copper is quite low in the reactivity series

So its not just gonna be copper then right... i mean if they say silver or platnium the same rule applies?? and what if they are really high in the reactivity series? would we be able to make a salt?

 

[gary221]

So its not just gonna be copper then right... i mean if they say silver or platnium the same rule applies?? and what if they are really high in the reactivity series? would we be able to make a salt?

yes, includes all non reactive metals.
n u will gt a salt ----> metal + acid = salt + hydrogen.

 

[Mariam879]

I facing a serious problem with paper 1 chemistry for some reason , any advice / tips/or anything to help me improve?

 

[Lockedin]

can u please tell me what topics from physics come in the ATP paper? (O-level) like in chemistry its mainly just Acids, Bases n Salts , Rate of reaction and Moles..
PLEASE HELP!

you can check out the syllabus for it

 

[mak kings]

Hey..ud any1 me in PHY PA.PA ............. Q11b in mj - p31 -2010 ...plz.plz1 !! any 1 ..i realy cnt understand it!!
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_s10_qp_31.pdf

 

[gary221]

Hey..ud any1 me in PHY PA.PA ............. Q11b in mj - p31 -2010 ...plz.plz1 !! any 1 ..i realy cnt understand it!!
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_s10_qp_31.pdf

We know that R = ρL/A
Since the diameter of the second wire(d2) is half the diameter of the first wire (d1), the area of the second wire(A2) is one fourth the area of the first wire(A1)
[as area = pi * (d/2)^2 ie pi *r^2]
So, R2 = (0.45/0.3) * R1
ρL2/(A1/4) = (0.45/0.3) * (ρL1/A1)
on solving, the two ρ n the A1 cancel each other out.
We get, 4L2 = 1.5 * L1
L2 = (1.5/4) * L1
L2 = 0.375 * L1
L2 = 37.5 % of L1
Hope u gt it!!

 

[Lockedin]

need 1993 paper 3 mark scheme for physics!

 

[CaveDweller65]

So its not just gonna be copper then right... i mean if they say silver or platnium the same rule applies?? and what if they are really high in the reactivity series? would we be able to make a salt?

Yes, the same rule applies with noble metals such as Platinum,Silver,Gold or those quite low in the reactivity series!
If they are high in the series, yes u can definitely prepare a salt, However metals such as Sodium and Potassium will result in a Very Dangerous Reaction!
Only M.A.Z.I.T metals (Magnesium, Aluminum, Zinc, Iron, Tin) are most suitable!

 

[GorgeousEyes]

Could anybody explain to me why when we use step up transformer the current is reduced so we use thinner and lighter cable ? i can't get what the relation between the current and the cables.

 

[gary221]

Could anybody explain to me why when we use step up transformer the current is reduced so we use thinner and lighter cable ? i can't get what the relation between the current and the cables.

the larger the current, the larger the heat losses.
since the current is reduced, thinner wires can be used, as the heat produced will be much less... so thin wires will not be melted.

 

[GorgeousEyes]

the larger the current, the larger the heat losses.
since the current is reduced, thinner wires can be used, as the heat produced will be much less... so thin wires will not be melted.

thanks

 

[GorgeousEyes]

paper 6 physics tips anyone ?

 

[Lockedin]

paper 6 physics tips anyone ?

I posted one document before look in a few previous pages
It has stuff to do with paper 6

 

[CaveDweller65]

Hey Guys!! I really need some help with this one.. Q.3 (c)
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_w10_qp_61.pdf

 

[Mariam879]

can any one help me
with w08 chemistry paper 3 Q7

 

[Henry Smith]

Hi guys,
Please help me to check out my answers for Paper 3 chemistry May/June 2012 and give me your feedback so I can improve my answers in the coming papers.

My worked paper can be grabbed from : https://www.yousendit.com/download/UVJpSkhVNkduSlFVV01UQw

Cheers