Here you go: http://www.freeexampapers.com/past_papers.php?l=Past_Papers/IGCSE/Chemistry/CIE/1993-2003/
Oh, I get it. Again, thanks a lot
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Physics, Chemistry and Biology: Post your doubts here!
- Thread starter semsemhosam
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Thanks a lot!
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hello i need to ask everyone something. The physics syllabus says that we have to learn the wave theory and apply it to refraction,reflection and diffraction ..and its not simply stating that the speed or wavelength etc changes or not but explains the theory behind it. And i dont get it. Please help!
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in all cases ( frequecy remains same).......in refraction (when the light goes from light to denser medium direction changes, speed decreases, wavelength decreases) ...in reflection ( the waves touch the surface and bouce back (direction changes,speed remain same,wavelenght remains same)......whereas diffraction depend upon the gap through which waves goo ( wider the gap, diffraction is insignificant,slight diffraction at the edges of waves)...( smaller the gap , more diffraction,...waves will be circular in motion)......
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thnx a lot but i was referring to the wave theory..u know wavelets etc?
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r u giving GCSE OR IGCSE?.....( I THINK WAVELET IS NOT IN OUR SYLLABUS).>>>>...
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im giving igcse. I have the study guide for igcse physics and physics nelson thornes book "for IGCSE" and they both talk about wavelets. Im a little confused.
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I have a doubt in chemistry...
In Paper3 October 2006 , question 7 a (ii)
Shouldn't the final point be lower than than that in the original reaction, as he is using ethanoic acid( weak acid) so it will give out less hydrogen ions?
But in mark scheme they said said same final point, why is that ?
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w06_qp_3.pdf
Also in question 8 c (iii) : what is the test and how did you come up to this answer?
In Paper3 October 2006 , question 7 a (ii)
Shouldn't the final point be lower than than that in the original reaction, as he is using ethanoic acid( weak acid) so it will give out less hydrogen ions?
But in mark scheme they said said same final point, why is that ?
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w06_qp_3.pdf
Also in question 8 c (iii) : what is the test and how did you come up to this answer?
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See in the original reaction there's one magnesium ribbon with HCL and then in 7aii) the experiment is repeated with one magnesium ribbon again but with ethanoic acid right? The mass of magnesium is the same so volume of hydrogen produced should be the SAME but the RATE OF REACTION IS SLOWER cuz the acid is weaker than HCL. The curve will be less, and not steep but the line should be ending at the same point.
As for question 8...can u see fat1 has H33 and the fat2 has 35? It makes u think that fat2 obviously doesnt have the total hydrogen atoms in its structure, just like an alkene. Therefore bromine water test- with fat 1 bromine changes from brown to colourless but fat 2 it stays brown.
*phew*
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sum1 pls help wid these qs if they can.......
A section of the macromolecular structure of silicon(IV) oxide is given below
Use this diagram to explain why the formula is SiO2 not SiO4.
(iii) Compare the structure of a protein with that of a synthetic polyamide. The structure
of a typical protein is given below.
How are they similar?
How are they different?
A section of the macromolecular structure of silicon(IV) oxide is given below
Use this diagram to explain why the formula is SiO2 not SiO4.
(iii) Compare the structure of a protein with that of a synthetic polyamide. The structure
of a typical protein is given below.
How are they similar?
How are they different?
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ok i think i remember these questions..... for the first one, say that each silicon atom is bonded to 4 other oxygen atoms and each oxygen atoms is bonded to two other silicon atoms. And also silicon has a valency of four and oxugen two right? So silicon (4) oxide has the molecular formula of Si2O4 when u swap their valencies. Now cancel down the numbers and voila- u get Sio2.
Second question: how they are similar? Well they both form the amide linkage [-HN-C=O].
Different? Synthetic proteins got a dicarboxylic acid group and diamine group as monomers. (Di means two). Natural proteins have only one amine group and one carboxylic acid group on either side.
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What are the most important topics to revise for chemistry extended please??? I am afraid i will fail the exam....
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honestly EVERYTHING is important, every slight detail like "an element that is yellow, which is sulphur". Dont know which paper that came in. Well kumiko, you better start learning, no selective study wen doing IGCSE!
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Wa alaikum Assalam wa rahmatullahAssalam-o-Alaikum.
Post your Physics, Chemistry and Biology doubts in here and members, along with me will try there best to help you out.
can u help me understand the concept of logic gates in circuits with potential dividers/LDRs/thermistors?
{Physics/IGCSE/CIE...}
Jazakillah
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Okie... thanks. I try my best then
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Gates:
NOT gate : it has only 1 input , and one output , if input is ON , then the output if OFF , if the input is OFF the output will be ON AND gate : 2 inputs 1 output , if the inputs is ON "and" ON , then the output will be ON , anything else will be OFF
OR gate: 2 inputs 1 output , if the inputs are anything but both OFF , then the o/p will be ON , ;.e. 1+0=1 , 0+1=1 , 1+1=1, 0+0=0 .
NOR gate : it is OR and NOT gates combined . i.e. it is the opposite of the OR gate
NAND gate : it is AND and NOT gates combined i.e. it is the opposite of the AND gate .
hope u got what i mean
oh and with any component , if u got the logic gates , then i think u can now know if the components will work or no
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Jazakillah, i got dat, but when they appear in circuits with potential dividers or resistors, i just get everything wrong.Gates:NOT gate : it has only 1 input , and one output , if input is ON , then the output if OFF , if the input is OFF the output will be ON
AND gate : 2 inputs 1 output , if the inputs is ON "and" ON , then the output will be ON , anything else will be OFF
OR gate: 2 inputs 1 output , if the inputs are anything but both OFF , then the o/p will be ON , ;.e. 1+0=1 , 0+1=1 , 1+1=1, 0+0=0 .
NOR gate : it is OR and NOT gates combined . i.e. it is the opposite of the OR gate
NAND gate : it is AND and NOT gates combined i.e. it is the opposite of the AND gate .
hope u got what i mean
oh and with any component , if u got the logic gates , then i think u can now know if the components will work or no
And please pray for all of us.
Jazakillah again
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i DO pray for u all , u also remember me in your prayersJazakillah, i got dat, but when they appear in circuits with potential dividers or resistors, i just get everything wrong.
And please pray for all of us.
Jazakillah again
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I will, Insha Allah.i DO pray for u all , u also remember me in your prayers