Physics, Chemistry and Biology: Post your doubts here!

[thats_me]

Of the surroundings, yes.
Of the reaction mixture, it's the opposite

Oh oki thx

 

[thats_me]

Q.28 in oct/nov 1996 and Q.28 J96
they are both approx the same but different answers :/

Both of them are aluminium resists corrosion and used for food containers

 

[Manobilly]

Good luck evry1 who has chemistry today!

 

[Mohsin41]

yess atlast done with last chemistry paper it was great. in this paper question 10 to 20 was having a siries like CCCBCCDDC

 

[NIM]

Guys how was bio and chem paper 1...

 

[EpicLol]

Guys how was bio and chem paper 1...

quite easy.....I think I lost 3-4 marks.....or maybe max 5

 

[waleed82]

guyz can anyone of u plz send me some links for chemistry preperation!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[waleed82]

quite easy.....I think I lost 3-4 marks.....or maybe max 5

i think physics paper 3 was preety hard of IGCSE!!!!!!!!!!!!!!! ryt!!!!!!!!

 

[mrroland]

Dear Physics Students,

Check out fuchunphysics.wordpress.com
This blog contains teaching videos for Physics O' Level syllabus.
Chapters uploaded include:
1) Measurements
2) Kinematics
3) Dynamics
4) Mass, Weight and Density
5) Turning Effect of Force
6) Energy, Work and Power
7) Pressure
8) Kinetic model of matter

The teaching videos for the remaining chapters will be posted soon.​

 

[waleed82]

Dear Physics Students,​

​

Check out fuchunphysics.wordpress.com​

This blog contains teaching videos for Physics O' Level syllabus.​

Chapters uploaded include:​

1) Measurements​

2) Kinematics​

3) Dynamics​

4) Mass, Weight and Density​

5) Turning Effect of Force​

6) Energy, Work and Power​

7) Pressure​

8) Kinetic model of matter​

​

The teaching videos for the remaining chapters will be posted soon.​

WELL CAN U PLZ HELP ME IN MATHS BIO N CHEMISTRY!!!!!!!

 

[ChemWhiz xoxo]

ChemWhiz here! Ive a question for u... Is the reaction with sodium (or any alkali metal) and water endothermic or exothermic? Past papers seem to say it's endothermic but my sources say its exo... If u can answer this, pls gimme the explanation as well...
Urs one and only,
ChemWhiz xoxo

 

[KyleoAhsan]

Lets evaluate and try to get some logical answers for it!

Lets take Sodium as an example:

2Na + 2H2O ---> 2NaOH + H2

The reaction between Sodium and water is very vigorous!

It should be Exothermic... Since the addition of Sodium to water will produce a lot of energy i.e. Heat Energy...

And I believe that Exothermic reactions are reactions in which heat energy is produced.. i.e. In exothermic reactions heat energy is released to the surroundings...if we carry out an experiment to see if addition of sodium to water is exothermic or endothermic...we can see that as we add sodium to water a lot energy is released with hydrogen gas!
Here is a video :- http://www.youtube.com/watch?v=JD85OUkEKKw

Do not try the experiment at home...The reaction is very violent!

Hope I helped

 

[ChemWhiz xoxo]

Yes.. u helped alrity.. Thank u..

 

[ChemWhiz xoxo]

Heyy... ChemWhiz here again..
I'd lyk to knw some more about the limiting factors on photosynthesis...
Dnt tell anyone bt our bio teacher's terrible.. :/
Id really apreciate it...

Urs one and truly,
ChemWhiz xoxo

 

[KyleoAhsan]

Heyy... ChemWhiz here again..
I'd lyk to knw some more about the limiting factors on photosynthesis...
Dnt tell anyone bt our bio teacher's terrible.. :/
Id really apreciate it...

Urs one and truly,
ChemWhiz xoxo

Once again let me try to help you!

So basically a limiting factor is a factor that if it is increased the rate of reaction increases...
For instance : If the light intensity is the limiting factor
- As you increase the light intensity the rate of photosynthesis increases
* But there comes a point where increase in light intensity does not increase the rate of reaction *
- That is called ( In this case ) Light saturation point so at this point further increase in light intensity makes a small difference to the speed of reaction. And at this point one of the other two factors is limiting the rate of reaction NOTE: At light saturation point all the chloroplasts are occupied in light absorption.
- Now why it doesn't increase the rate of reaction is that because another factor is now the limiting factor! for example Carbondioxide concentration..as you increase the Carbondioxide concentration the rate of photosynthesis increases and then again there comes a point where increase in Carbondioxide does not increase the rate of reaction.
- So the graph shows a increasing gradient and then at the saturation point it becomes more or less constant!

 

[ChemWhiz xoxo]

So let me get this strait... there are only 2 limiting factors for phtsynthesis?? :S

 

[KyleoAhsan]

So let me get this strait... there are only 2 limiting factors for phtsynthesis?? :S

Nope! There are many I think...but for our syllabus I believe we only need to know 3 and they are:

1. Light Intensity
2. Temperature
3. Carbondioxide Concentration

Well in the syllabus it says Understand the concept of limiting factors...

It works like this: when one factor is limiting...as that factor increases the rate of photosynthesis increases up to a certain point and then another factor becomes the limiting factor...!

 

[ChemWhiz xoxo]

Thanks..once agin...that helped..

 

[Xeeshan Rahat]

I am thinking that what would be supplied by CIE in my IGCSE Chemistry exam, I know a PERIODIC TABLE will be provided but what other stuff, I am confused ! I will be going for extended course i.e. Paper 1, 3 & 6 .xD.

 

[ChemWhiz xoxo]

Even im takin the xtended course... u will be allowed to take a calculator... some geometrical instruments, a pencil ( the HB kind) and a blue pen ... bt no correctors are allowed...