Physics, Chemistry and Biology: Post your doubts here!

[joulie]

plz from where can i get mark scheme of biology paper 1 1994-1999

 

[Ahmed Khider]

helppp plzzz plzzz help me​

may 1995
29 why A not D

nov 1997 19 why C not B
25 why A not C
36 why C not D i think the ms is wrong :/

June 1998 4 why D not C
15 its D but i don't understand why i don't understand how did the ms get to the answer :'(

nov 1998
11 why A not D
15 why A not C
35 why A not B
37 why A not D

may 1999
24 why A not B

nov 1999
21 i don't understand the question and what should we think about to get the answer btw its C

j 2000
17 there r 2 answers D and B so why is it D

PLZZZZ HELPP ME I REALLY NEED UR HELPPPP PLZZZZZZ HELP ME :'(

Hey srry 4 the late reply. In may 1995 qno 29 its A as low density is needed becoz this is an airplane flying in high altitudes so it would need something which is light. It isnt D becoz a high strength means high mass which will definitely slow down the airplane!. In nov 1997,question 19 u r rite it should be C..i dunno why it is B becoz as far as i knw a yellow ppt is when Lead iodide is formed!!. As for qno 36 in the same year, i think u opened the wrong ms..it can neva be C unless there is a new type of alkane discovered which i never heard of . In may 1998 qno 4..think about it u have to use a thermometer so the ans is either C or D..then think about it again..u need to measure the temperature change over a given amount of time and so u need a clock and btw C is just a distraction because u can measure the volume with anything and overall measuring the volume is not as important as measuring the time. In qno 15 in the same year, the definition of oxidation if you recall it is the gain of oxygen or the loss of hydrogen so the answer has to be D . For qno11 in nov 1998, im nt sure but i just took it as common sense as A is methane and it is used as a fuel in some countries so it has to give the most water per carbon but im still nt sure u might wanna ask some1 else. As for qno 15 i really dont know y the ans is A..r u sure ur opening the right ms??? For question no 35..it already says in the question that slaked lime is used to neutralise an acidic soil and an acidic soil has a pH less than 8 and a neutralisation reaction ends up with a neutral product i.e the soil is made neutral at the end of this process which is why the ans is A not B. As for question no 37..ive solved this question many times n the ans is definitely D,make sure u dnt have a typing mistake in ur ms or that u opened the right ms!! In may1999 qno 24 i can assure u that there is something wrong with ur ms becoz the reactivity of metals increases downwards while the reactivity of non-metals increases upwards!! In nov 1999 qno 21..at first sight all three options are rite however the 1st option( potassium metal) is not practical at all becoz Potassium is a very reactive metal and reacting it with an acid can be very dangerous which makes only the other 2 options more reliable to use. In j2000 qno 17..The answer is D because N2 gained 2 oxygen atoms to become No2 while in B N2O4 lost 4 oxygen atoms which is reduction not oxidation. P.s I insist that u check that ms is the rite one or not!!

 

[za Shadow]

Hey srry 4 the late reply. In may 1995 qno 29 its A as low density is needed becoz this is an airplane flying in high altitudes so it would need something which is light. It isnt D becoz a high strength means high mass which will definitely slow down the airplane!. In nov 1997,question 19 u r rite it should be C..i dunno why it is B becoz as far as i knw a yellow ppt is when Lead iodide is formed!!. As for qno 36 in the same year, i think u opened the wrong ms..it can neva be C unless there is a new type of alkane discovered which i never heard of . In may 1998 qno 4..think about it u have to use a thermometer so the ans is either C or D..then think about it again..u need to measure the temperature change over a given amount of time and so u need a clock and btw C is just a distraction because u can measure the volume with anything and overall measuring the volume is not as important as measuring the time. In qno 15 in the same year, the definition of oxidation if you recall it is the gain of oxygen or the loss of hydrogen so the answer has to be D . For qno11 in nov 1998, im nt sure but i just took it as common sense as A is methane and it is used as a fuel in some countries so it has to give the most water per carbon but im still nt sure u might wanna ask some1 else. As for qno 15 i really dont know y the ans is A..r u sure ur opening the right ms??? For question no 35..it already says in the question that slaked lime is used to neutralise an acidic soil and an acidic soil has a pH less than 8 and a neutralisation reaction ends up with a neutral product i.e the soil is made neutral at the end of this process which is why the ans is A not B. As for question no 37..ive solved this question many times n the ans is definitely D,make sure u dnt have a typing mistake in ur ms or that u opened the right ms!! In may1999 qno 24 i can assure u that there is something wrong with ur ms becoz the reactivity of metals increases downwards while the reactivity of non-metals increases upwards!! In nov 1999 qno 21..at first sight all three options are rite however the 1st option( potassium metal) is not practical at all becoz Potassium is a very reactive metal and reacting it with an acid can be very dangerous which makes only the other 2 options more reliable to use. In j2000 qno 17..The answer is D because N2 gained 2 oxygen atoms to become No2 while in B N2O4 lost 4 oxygen atoms which is reduction not oxidation. P.s I insist that u check that ms is the rite one or not!!

THANK U VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVEEEEEEEEEEEEEEEEEEEEEEEEEEERRRRRRRRRRRRRRRRRRRRRRRRYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY MUCH DUNNO WHAT TO SAY..........U RRRRRRRRRRRRRRRR THE BEST THANK U !!!!!
I AM ALSO SURE THAT MY MS IS WRONG AS I GOT IT FROM THE INTERNET AND THANKS AGAIN

 

[Ahmed Khider]

THANK U VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVEEEEEEEEEEEEEEEEEEEEEEEEEEERRRRRRRRRRRRRRRRRRRRRRRRYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY MUCH DUNNO WHAT TO SAY..........U RRRRRRRRRRRRRRRR THE BEST THANK U !!!!!
I AM ALSO SURE THAT MY MS IS WRONG AS I GOT IT FROM THE INTERNET AND THANKS AGAIN

Ur welcome its my pleasure to help you

 

[Iridescent]

In the electrolytic cell, we use conventional current direction (positive to the negative terminal) or electron flow (negative to positive terminal) for the current in the external circuit?
Thanx!

 

[Ahmed Khider]

In the electrolytic cell, we use conventional current direction (positive to the negative terminal) or electron flow (negative to positive terminal) for the current in the external circuit?
Thanx!

In the electrolytic cell, we use conventional current direction (positive to the negative terminal) or electron flow (negative to positive terminal) for the current in the external circuit?
Thanx!

For the external circuit you use the convectional current direction. Btw u r talking about a normal electrolysis cell rite??

 

[Abu mota]

Hey srry 4 the late reply. In may 1995 qno 29 its A as low density is needed becoz this is an airplane flying in high altitudes so it would need something which is light. It isnt D becoz a high strength means high mass which will definitely slow down the airplane!. In nov 1997,question 19 u r rite it should be C..i dunno why it is B becoz as far as i knw a yellow ppt is when Lead iodide is formed!!. As for qno 36 in the same year, i think u opened the wrong ms..it can neva be C unless there is a new type of alkane discovered which i never heard of . In may 1998 qno 4..think about it u have to use a thermometer so the ans is either C or D..then think about it again..u need to measure the temperature change over a given amount of time and so u need a clock and btw C is just a distraction because u can measure the volume with anything and overall measuring the volume is not as important as measuring the time. In qno 15 in the same year, the definition of oxidation if you recall it is the gain of oxygen or the loss of hydrogen so the answer has to be D . For qno11 in nov 1998, im nt sure but i just took it as common sense as A is methane and it is used as a fuel in some countries so it has to give the most water per carbon but im still nt sure u might wanna ask some1 else. As for qno 15 i really dont know y the ans is A..r u sure ur opening the right ms??? For question no 35..it already says in the question that slaked lime is used to neutralise an acidic soil and an acidic soil has a pH less than 8 and a neutralisation reaction ends up with a neutral product i.e the soil is made neutral at the end of this process which is why the ans is A not B. As for question no 37..ive solved this question many times n the ans is definitely D,make sure u dnt have a typing mistake in ur ms or that u opened the right ms!! In may1999 qno 24 i can assure u that there is something wrong with ur ms becoz the reactivity of metals increases downwards while the reactivity of non-metals increases upwards!! In nov 1999 qno 21..at first sight all three options are rite however the 1st option( potassium metal) is not practical at all becoz Potassium is a very reactive metal and reacting it with an acid can be very dangerous which makes only the other 2 options more reliable to use. In j2000 qno 17..The answer is D because N2 gained 2 oxygen atoms to become No2 while in B N2O4 lost 4 oxygen atoms which is reduction not oxidation. P.s I insist that u check that ms is the rite one or not!!

i agree with u the ms has lots of mistakes for some reason but i dont agree with u on the question in may 1995 because strength is needed for airplanes as otherwise they will just choose any other metal other than aluminium with a lower density and there are alot, and so what distinguishes aluminium from other metals is that it is light but it is still strong and so the answer he wrote is actually right
and Q.15 in june 1998 it is actually neutralisation because in neutralisation the acid loses its hydrogen atoms becoming a totally different substance, i think oxidation is wrong because it is technically not a process it is a result of a process.
Q.4 it is C bro u dont need time at all because ur not measuring rate ur just measuring temperature change there is no need whatsoever for a clock and u actually need a burette because it said that volumes have to be equal and burette is the most accurate
for nov 1998
Q.11 it is A (btw i didnt know it too thats me explained it to me on a previous page but i will explain it again ) each carbon is surrounded by only 3 hydrogens in each except in methane this means that methane will produce two water molecules but the others will produce only one water molecule ( u need two hydrogens for each water molecule)
for Q.15 C is correct it is a wrong answer in the ms
for Q.24 in may 1999 for metals reactivity increases down the group but for non-metals reactivity decreases down the group, the question is erased so i dont know what is the correct answer but this is the correct concept
for may/june 2000 Q.17 it is D because N2O4 is the same as NO2 (remember u always need to simplify it)
i hope u dont mind me correcting u and also if u disagree with me,reply here and maybe u can convince me or i can , imnot a scientist i can be wrong

 

[Abu mota]

can someone explaine this plz :-biology paper 1 year 2000 mayjune
question 27 why the increase in mass only occured at the end
and question 17 i dont even understand what is the difference between "p"and "q"
and in year 2001 may june question 38 ??????

for may/june 2000 Q.17 the difference between them is that Q has a wider opening than P and this can only be caused when the plant has alot of factors than enable it to photosynthesis rapidly like high light intesity or high CO2 concentration and in the question all decrease the rate of photosynthesis or has no effect at all except B which increase it and so the answer is B.
for Q,27 the answer is C because this the only position in which the plant can photosynthesise i.e its leaves are above the ground exposed to light and the plant can only grow using photosynthesis.
in may/june 2001 Q.38 the answer is C because firstly what is human sewage, it is the results of excretion and as you know a big part of the nitrogen cycle is the excretion and as we for some reason considered as animals in IGCSE biology then it is C (also remember our excretory products are converted into nitrates by nitrifying bacteria and such and so it is nitrates in the soil and water)
if u dont understand ask again, i actually found it very hard to explain the answers because i cudnt put it into words and so if u still dont understand plz ask again
EDIT: i just checked the mark scheme and all of the answers are correct except Q.27 and i have abosolutely no idea why it is D not C srry :/
EDIT again : i looked deeper into the question now and i found why it is D, it is D because at A,B,C it is only using the stored starch inside the tuber and converting it to grow, it is still not making it's own food by photosynthesis and so there is no actual change in mass as it is just converting what it already has, however at D it has increased in mass , u can see that because it has alot of leaves which can photosynthesise and also alot of tubers were made, althought the tuber at the start was already used up.did u understand it?

 

[Hammad Siddiqi]

Hi... You can earn online during your summer vacations
read the blog
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[The sun]

plz from where can i get mark scheme of chemistry paper 1 from 1993-1999

 

[Iridescent]

For the external circuit you use the convectional current direction. Btw u r talking about a normal electrolysis cell rite??

yes but in one of the guides they have shown electron flow arrows!

 

[Ahmed Khider]

i agree with u the ms has lots of mistakes for some reason but i dont agree with u on the question in may 1995 because strength is needed for airplanes as otherwise they will just choose any other metal other than aluminium with a lower density and there are alot, and so what distinguishes aluminium from other metals is that it is light but it is still strong and so the answer he wrote is actually right
and Q.15 in june 1998 it is actually neutralisation because in neutralisation the acid loses its hydrogen atoms becoming a totally different substance, i think oxidation is wrong because it is technically not a process it is a result of a process.
Q.4 it is C bro u dont need time at all because ur not measuring rate ur just measuring temperature change there is no need whatsoever for a clock and u actually need a burette because it said that volumes have to be equal and burette is the most accurate
for nov 1998
Q.11 it is A (btw i didnt know it too thats me explained it to me on a previous page but i will explain it again ) each carbon is surrounded by only 3 hydrogens in each except in methane this means that methane will produce two water molecules but the others will produce only one water molecule ( u need two hydrogens for each water molecule)
for Q.15 C is correct it is a wrong answer in the ms
for Q.24 in may 1999 for metals reactivity increases down the group but for non-metals reactivity decreases down the group, the question is erased so i dont know what is the correct answer but this is the correct concept
for may/june 2000 Q.17 it is D because N2O4 is the same as NO2 (remember u always need to simplify it)
i hope u dont mind me correcting u and also if u disagree with me,reply here and maybe u can convince me or i can , imnot a scientist i can be wrong

Lol r u kidding me of course i dnt mind u correcting me DD Im a person and i can definitely be wrong thanx for correcting me. In the question about the Endothermic or exothermic i explained it to him based on the answer he gave me n god knows who is right becoz up to know i cant find the right ms for these old papers. In q4 u r rite i thought of it in another way and i am apparently wrong but how about u try to find the right ms for these papers becoz im still confused in some questions. Thx once again for correcting me! In may 1995 i dunno but i think strength means a metal with a higher density and i read in many notes that aluminuim (i think i spelt it wrong) is used in airplanes becoz of its low density not becoz of its strength.Thx once again for correcting me

 

[za Shadow]

i agree with u the ms has lots of mistakes for some reason but i dont agree with u on the question in may 1995 because strength is needed for airplanes as otherwise they will just choose any other metal other than aluminium with a lower density and there are alot, and so what distinguishes aluminium from other metals is that it is light but it is still strong and so the answer he wrote is actually right
and Q.15 in june 1998 it is actually neutralisation because in neutralisation the acid loses its hydrogen atoms becoming a totally different substance, i think oxidation is wrong because it is technically not a process it is a result of a process.
Q.4 it is C bro u dont need time at all because ur not measuring rate ur just measuring temperature change there is no need whatsoever for a clock and u actually need a burette because it said that volumes have to be equal and burette is the most accurate
for nov 1998
Q.11 it is A (btw i didnt know it too thats me explained it to me on a previous page but i will explain it again ) each carbon is surrounded by only 3 hydrogens in each except in methane this means that methane will produce two water molecules but the others will produce only one water molecule ( u need two hydrogens for each water molecule)
for Q.15 C is correct it is a wrong answer in the ms
for Q.24 in may 1999 for metals reactivity increases down the group but for non-metals reactivity decreases down the group, the question is erased so i dont know what is the correct answer but this is the correct concept
for may/june 2000 Q.17 it is D because N2O4 is the same as NO2 (remember u always need to simplify it)
i hope u dont mind me correcting u and also if u disagree with me,reply here and maybe u can convince me or i can , imnot a scientist i can be wrong

thank u 4 ur help rrrrrrrrreeeeeeeeeeeeaaaaaaaaaaaaaallllllllllllllllllllyyyyyyyyyyyyyyyyyyyy appreciate it

 

[Abu mota]

Lol r u kidding me of course i dnt mind u correcting me DD Im a person and i can definitely be wrong thanx for correcting me. In the question about the Endothermic or exothermic i explained it to him based on the answer he gave me n god knows who is right becoz up to know i cant find the right ms for these old papers. In q4 u r rite i thought of it in another way and i am apparently wrong but how about u try to find the right ms for these papers becoz im still confused in some questions. Thx once again for correcting me! In may 1995 i dunno but i think strength means a metal with a higher density and i read in many notes that aluminuim (i think i spelt it wrong) is used in airplanes becoz of its low density not becoz of its strength.Thx once again for correcting me

it is used because of its high strength to weight ratio, i just saw it on a website and there is actually only one mark scheme on the internet sadly

 

[Ahmed Khider]

it is used because of its high strength to weight ratio, i just saw it on a website and there is actually only one mark scheme on the internet sadly

Its ok ill try to find a question like that and c its answer

 

[Skynox]

Its ok ill try to find a question like that and c its answer

It was repeated and aluminium is used for its low density and strength when it is in alloy with magneisum..

 

[joulie]

for may/june 2000 Q.17 the difference between them is that Q has a wider opening than P and this can only be caused when the plant has alot of factors than enable it to photosynthesis rapidly like high light intesity or high CO2 concentration and in the question all decrease the rate of photosynthesis or has no effect at all except B which increase it and so the answer is B.
for Q,27 the answer is C because this the only position in which the plant can photosynthesise i.e its leaves are above the ground exposed to light and the plant can only grow using photosynthesis.
in may/june 2001 Q.38 the answer is C because firstly what is human sewage, it is the results of excretion and as you know a big part of the nitrogen cycle is the excretion and as we for some reason considered as animals in IGCSE biology then it is C (also remember our excretory products are converted into nitrates by nitrifying bacteria and such and so it is nitrates in the soil and water)
if u dont understand ask again, i actually found it very hard to explain the answers because i cudnt put it into words and so if u still dont understand plz ask again
EDIT: i just checked the mark scheme and all of the answers are correct except Q.27 and i have abosolutely no idea why it is D not C srry :/
EDIT again : i looked deeper into the question now and i found why it is D, it is D because at A,B,C it is only using the stored starch inside the tuber and converting it to grow, it is still not making it's own food by photosynthesis and so there is no actual change in mass as it is just converting what it already has, however at D it has increased in mass , u can see that because it has alot of leaves which can photosynthesise and also alot of tubers were made, althought the tuber at the start was already used up.did u understand it?

thanks alot u made it so simple

 

[Ahmed Khider]

i agree with u the ms has lots of mistakes for some reason but i dont agree with u on the question in may 1995 because strength is needed for airplanes as otherwise they will just choose any other metal other than aluminium with a lower density and there are alot, and so what distinguishes aluminium from other metals is that it is light but it is still strong and so the answer he wrote is actually right
and Q.15 in june 1998 it is actually neutralisation because in neutralisation the acid loses its hydrogen atoms becoming a totally different substance, i think oxidation is wrong because it is technically not a process it is a result of a process.
Q.4 it is C bro u dont need time at all because ur not measuring rate ur just measuring temperature change there is no need whatsoever for a clock and u actually need a burette because it said that volumes have to be equal and burette is the most accurate
for nov 1998
Q.11 it is A (btw i didnt know it too thats me explained it to me on a previous page but i will explain it again ) each carbon is surrounded by only 3 hydrogens in each except in methane this means that methane will produce two water molecules but the others will produce only one water molecule ( u need two hydrogens for each water molecule)
for Q.15 C is correct it is a wrong answer in the ms
for Q.24 in may 1999 for metals reactivity increases down the group but for non-metals reactivity decreases down the group, the question is erased so i dont know what is the correct answer but this is the correct concept
for may/june 2000 Q.17 it is D because N2O4 is the same as NO2 (remember u always need to simplify it)
i hope u dont mind me correcting u and also if u disagree with me,reply here and maybe u can convince me or i can , imnot a scientist i can be wrong

I checked the answer for the question which says what is the process that results in the loosing of a hydrogen atom and the answer is Oxidation (D)......

 

[Abu mota]

I checked the answer for the question which says what is the process that results in the loosing of a hydrogen atom and the answer is Oxidation (D)......

From which mark scheme?

 

[Ahmed Khider]

i agree with u the ms has lots of mistakes for some reason but i dont agree with u on the question in may 1995 because strength is needed for airplanes as otherwise they will just choose any other metal other than aluminium with a lower density and there are alot, and so what distinguishes aluminium from other metals is that it is light but it is still strong and so the answer he wrote is actually right
and Q.15 in june 1998 it is actually neutralisation because in neutralisation the acid loses its hydrogen atoms becoming a totally different substance, i think oxidation is wrong because it is technically not a process it is a result of a process.
Q.4 it is C bro u dont need time at all because ur not measuring rate ur just measuring temperature change there is no need whatsoever for a clock and u actually need a burette because it said that volumes have to be equal and burette is the most accurate
for nov 1998
Q.11 it is A (btw i didnt know it too thats me explained it to me on a previous page but i will explain it again ) each carbon is surrounded by only 3 hydrogens in each except in methane this means that methane will produce two water molecules but the others will produce only one water molecule ( u need two hydrogens for each water molecule)
for Q.15 C is correct it is a wrong answer in the ms
for Q.24 in may 1999 for metals reactivity increases down the group but for non-metals reactivity decreases down the group, the question is erased so i dont know what is the correct answer but this is the correct concept
for may/june 2000 Q.17 it is D because N2O4 is the same as NO2 (remember u always need to simplify it)
i hope u dont mind me correcting u and also if u disagree with me,reply here and maybe u can convince me or i can , imnot a scientist i can be wrong

And also for the question about the apparatus needed in the exothermic and the endothermic question ur rite..Can u believe i didn't read the part which says "mixing equal volumes of the 2 solutions"!!!!