Physics, Chemistry and Biology: Post your doubts here!

[niassu]

the syllabus mentions this point 2.1 which I would like to know about it :
Know that here are other classification
systems e.g. cladistics (based on RNA/
DNA sequencing data)






plz help exams are soon

 

[AtemisDelta]

q. the speed of sound waves in air may be determined by experiment usin a source that generates light n sound waves at the same time.
draw a labelled diagram of da arrangement of suitable apparatus for da experiment.
state the readings you would take
explain how you would calculate the speed of sound in air usin your readings.

q2. in an experiment to measureda distanc ebetweena thunderstorm an an individual(observer), why is light not taken into calculation?

pls any1 ans as soon as possible.

 

[AtemisDelta]

sum 1 pls help wid da followin qs........

 

[Praise]

Thanx!

I think that the chloride should be first reacted off by reacting the aluminium chloride with sodium hydroxide, which displaces chlorine from aluminium chloride resulting to aluminium hydroxide which can then be passed through electrolysis.

The equation:
aluminium chloride+sodium hydroxide = aluminium hydroxide+sodium chloride.

 

[Praise]

q. the speed of sound waves in air may be determined by experiment usin a source that generates light n sound waves at the same time.
draw a labelled diagram of da arrangement of suitable apparatus for da experiment.
state the readings you would take
explain how you would calculate the speed of sound in air usin your readings.

q2. in an experiment to measureda distanc ebetweena thunderstorm an an individual(observer), why is light not taken into calculation?

pls any1 ans as soon as possible.

Q(1)Suitable apparatus needed,A light source,a sound source(a speaker),a microphone, a light detector(ur eye, or a photoelectric detector,e.t.c), a stopwatch.a rule.
Arrangement: the sound and light sources are placed at the same point on a table, the meter rule is used to measure the distance between the sources and detectors.The detectors would be directly in front of the sources.

Readings:
Distance between the sources and the detectors,
time taken for the sound to be detected by the mic.
time taken for the light to be detected by the light detector(Light dependent diode)

Calculations: speed of sound in air assuming that there are no obstructions=distance divided by time taken

Q(2)
light travels at a greater speed than sound (at 300000000 m/s) and therefore would be uneasy to account for

 

[niassu]

the syllabus mentions this point 2.1 which I would like to know about it :
Know that here are other classification
systems e.g. cladistics (based on RNA/
DNA sequencing data)






plz help exams are soon

helloo.......... anyone who took biology please I need help

 

[purplerox]

gimme resources fro p6 na..!!

 

[Iridescent]

Does anyone have a list of the colours for the different elements/compounds?
Like sometimes they will ask you for the colour for copper carbonate etc.

Copper sulphate - Blue
Copper nitrate - Green
Copper oxide - Black
Copper carbonate - Blue
Iron(II) sulphate - Green
Iron(III) sulphate - Red-brown
Cobalt chloride - Pink
Can think of only these for now!

 

[GlitteringLights]

Describe the medicinal use of antibiotics for the treatment of bacterial infection. answer point-wise preferred and please include all we need to know regarding this question
THANK YOU

 

[Yousif Mukkhtar]

Guys, in ON11 Paper 61 for Physics. In question (d) how can I get the correct answer? I got the gradient as 133. But in the marking scheme it says the answer is between 0.9-2.5.

 

[Moar]

I have two Biology doubts ,both are in cambridge o.l igcse paper 3 exams:
1- In june 2007 , question no.5 it shows that the number of black moths caught 36, and the number of pale, speckled moths 82. Shouldn't the number of pale, speckled moths be less than that of the black moths. I mean the pale, speckled should be able to camouflage on the pale barks of the trees...
2- In June 2008 question 4 (a) why can't i say check if they have different external features ?
links for the two exams: 1-http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Biology (0610)/0610_s07_qp_3.pdf
2- http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Biology (0610)/0610_s08_qp_3.pdf
Thx in advance

 

[Moar]

Describe the medicinal use of antibiotics for the treatment of bacterial infection. answer point-wise preferred and please include all we need to know regarding this question
THANK YOU

Is this in o.l biology? Because we only have the idea of resistance of bacteria to antibiotics , but not medicinal use of it, am i missing out something ?

 

[GlitteringLights]

Is this in o.l biology? Because we only have the idea of resistance of bacteria to antibiotics , but not medicinal use of it, am i missing out something ?

EXACTLY ! i was thinking the same thing but it was on the syllabus outline :/
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Biology (0610)/0610_y12_sy.pdf
(pg. 33)

 

[Razo513]

I have two Biology doubts ,both are in cambridge o.l igcse paper 3 exams:
1- In june 2007 , question no.5 it shows that the number of black moths caught 36, and the number of pale, speckled moths 82. Shouldn't the number of pale, speckled moths be less than that of the black moths. I mean the pale, speckled should be able to camouflage on the pale barks of the trees...
2- In June 2008 question 4 (a) why can't i say check if they have different external features ?
links for the two exams: 1-http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Biology (0610)/0610_s07_qp_3.pdf
2- http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Biology (0610)/0610_s08_qp_3.pdf
Thx in advance

for no 5. u r completely right... & the way u thought of the question is on right track.. but see , the thing is that the results are after 2 WEEKS as the pale speckled camouflaged so predators cant eat or hunt them down as they r hard to observe , unlike the black moths with can be easily caught... so after the 2 weeks when the moths are to be collected more speckled moths are collected since they camouflaged or in other words hid well ... while in no 4.a) u cant mention external features because by eye species cant be determined .. plus u should know that same species have similar origins of DNA so . if the DNA was tested u can simply differ between 2 species , HOPE THAT I COULD HELP .. even if a bit

 

[Moar]

for no 5. u r completely right... & the way u thought of the question is on right track.. but see , the thing is that the results are after 2 WEEKS as the pale speckled camouflaged so predators cant eat or hunt them down as they r hard to observe , unlike the black moths with can be easily caught... so after the 2 weeks when the moths are to be collected more speckled moths are collected since they camouflaged or in other words hid well ... while in no 4.a) u cant mention external features because by eye species cant be determined .. plus u should know that same species have similar origins of DNA so . if the DNA was tested u can simply differ between 2 species , HOPE THAT I COULD HELP .. even if a bit

I feel soo stupid
anyway thx alot

 

[Moar]

EXACTLY ! i was thinking the same thing but it was on the syllabus outline :/
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Biology (0610)/0610_y12_sy.pdf
(pg. 33)

Well anyway i don't think you need to worry about it .Althought it is isn't in my biology notes, but it simply has the same idea of manufacture of SCP and of insulin, just the use of fermenter and providing suitable temperature and ventilation, food,pH ...etc then collect the filtrate.

 

[GlitteringLights]

Well anyway i don't think you need to worry about it .Althought it is isn't in my biology notes, but it simply has the same idea of manufacture of SCP and of insulin, just the use of fermenter and providing suitable temperature and ventilation, food,pH ...etc then collect the filtrate.

yeah me either :/ alright , but can it be assumed that it's also talking about what the antibiotic does to the bacteria as well as the process of extreacting it?
andddd thank you so much !

 

[Moar]

yeah me either :/ alright , but can it be assumed that it's also talking about what the antibiotic does to the bacteria as well as the process of extreacting it?
andddd thank you so much !

hmm looking back at your answer i am not so sure :\ I know the answer for what was mentioned in the syllabus is wat i said, but i think your question mean how does antibiotics fight bacterial infection. My guess is: non-mutant bacteria are killed by anti-biotics which can penetrate the bacteria's capsule and kill the bacteria which was causing the infection. But i am so unsure abt this , so its best to check the mark scheme and tell me what did you find good luck

 

[GlitteringLights]

hmm looking back at your answer i am not so sure :\ I know the answer for what was mentioned in the syllabus is wat i said, but i think your question mean how does antibiotics fight bacterial infection. My guess is: non-mutant bacteria are killed by anti-biotics which can penetrate the bacteria's capsule and kill the bacteria which was causing the infection. But i am so unsure abt this , so its best to check the mark scheme and tell me what did you find good luck

lol guess what! both answers were right :O http://www.xtremepapers.com/revision/gcse/biology/enzymes.php last 2 paragraphs

 

[Moar]

lol i am good/ lucky
Anyway glad you know it now, hope I've helped