Biology; Chemistry; Physics: Post your doubts here!

[Saad Mughal]

I'll be giving these exams in May-June 2014 ;D
How to ace them?

Which subjects are you taking? I can't say anything about Biology since I didn't appear in it.
How much of the Chemistry and Physics syllabus have you covered?

 

[Nabeel.Ahmad]

Which subjects are you taking? I can't say anything about Biology since I didn't appear in it.
How much of the Chemistry and Physics syllabus have you covered?

Physics, Chem, Bio, Maths, Addmaths, Eng, Urdu.

Chemistry --> Everything except Electro-Chemistry, Redox, Organic Chemistry.
Physics --> First 16 Chapters till ''Sound''..

 

[Saad Mughal]

Physics, Chem, Bio, Maths, Addmaths, Eng, Urdu.

Chemistry --> Everything except Electro-Chemistry, Redox, Organic Chemistry.
Physics --> First 16 Chapters till ''Sound''..

You've covered most of the syllabus, that's good.
Electro-Chemistry is very easy, pay particular attention to the discharge of ions (both anions and cations) in that chapter, it's the only thing that's very important.
Redox reactions are well, just a matter of reading the chapter, you should only know what oxidation and reduction is (all definitions), how to find out the oxidation state of each element in compounds and what types of reactions are redox.
Organic Chemistry, it's just boring. Very boring. That's all I can say.
Physics - the hardest section is Magnetism and Electricity. That's where you have to pay attention, all others are pretty easy.
My recommendation:
Buy Fundamental Chemistry - it has everything exactly according to the syllabus.
Buy Complete IGCSE Physics - it has very easy explanations and good examples.
Solve MCQ's (at least 15-20) of each chapter after you complete it!

 

[Nabeel.Ahmad]

You've covered most of the syllabus, that's good.
Electro-Chemistry is very easy, pay particular attention to the discharge of ions (both anions and cations) in that chapter, it's the only thing that's very important.
Redox reactions are well, just a matter of reading the chapter, you should only know what oxidation and reduction is (all definitions), how to find out the oxidation state of each element in compounds and what types of reactions are redox.
Organic Chemistry, it's just boring. Very boring. That's all I can say.
Physics - the hardest section is Magnetism and Electricity. That's where you have to pay attention, all others are pretty easy.
My recommendation:
Buy Fundamental Chemistry - it has everything exactly according to the syllabus.
Buy Complete IGCSE Physics - it has very easy explanations and good examples.
Solve MCQ's (at least 15-20) of each chapter after you complete it!

Should i strengthen my previous chapters or prepare the one's i haven't done yet, in the holidays?

 

[Saad Mughal]

Should i strengthen my previous chapters or prepare the one's i haven't done yet, in the holidays?

Strengthen and Practice (from book or papers) the previous chapters. Then, in class, when you complete the chapters then pay special attention to them and solve papers afterwards. That should be sufficient.

 

[Kamihus]

You've covered most of the syllabus, that's good.
Electro-Chemistry is very easy, pay particular attention to the discharge of ions (both anions and cations) in that chapter, it's the only thing that's very important.
Redox reactions are well, just a matter of reading the chapter, you should only know what oxidation and reduction is (all definitions), how to find out the oxidation state of each element in compounds and what types of reactions are redox.
Organic Chemistry, it's just boring. Very boring. That's all I can say.
Physics - the hardest section is Magnetism and Electricity. That's where you have to pay attention, all others are pretty easy.
My recommendation:
Buy Fundamental Chemistry - it has everything exactly according to the syllabus.
Buy Complete IGCSE Physics - it has very easy explanations and good examples.
Solve MCQ's (at least 15-20) of each chapter after you complete it!

Organic and boring, you're kidding, right?
Its except Macromolecules

 

[Saad Mughal]

Organic and boring, you're kidding, right?
Its except Macromolecules

Yeah, I meant Macromolecules and Petroleum.

 

[Kamihus]

No ratta? Yaar bachay ko Chemistry ATP ka tou batao, Computer ATC ka tou batao. Aese waisy no ratta?

Yep man Salts is more ratta than even Islamiat or History

 

[Kamihus]

Yeah, I meant Macromolecules and Petroleum.

The main part is actually alkanes, alkenes, alcohols and carboxylic acids.

 

[Saad Mughal]

The main part is actually alkanes, alkenes, alcohols and carboxylic acids.

Yeah, they're fun.

 

[Saad Mughal]

Yep man Salts is more ratta than even Islamiat or History

Every single thing in that chapter.

 

[irfan.kheerdali]

all frequent questions in organic chemistry and environment and atmosphere

 

[irfan.kheerdali]

may/june 2010 p22 qu. B10 answer plzzzzzz help

 

[Saad Mughal]

may/june 2010 p22 qu. B10 answer plzzzzzz help

You didn't mention the subject. -_-
Still though, here's the answer:

(a) (i) Acid needs to be Hydrochloric Acid, HCl.
Alkali can be Potassium Hydroxide, KOH.
Reaction --> HCl + KOH ---> KCl + H2O.

(ii) We need to describe how to produce SOLID potassium chloride. So:
Titration is done since both the base and the salt are soluble. Acid (HCl) is slowly added to the Alkali (KOH) until the alkali is neutralized. Hence, we obtain a solution of the salt KCl. We will then evaporate the solution to obtain solid KCl crystals.

(b) (i) Ammonium ion = NH4 + , Phosphate ion = PO4 -3, therefore:
Ammonium Phosphate = (NH4)3PO4.

(ii) Mr of Ammonium Phosphate = (14*3) + (1*4*3) + (31*1) + (16*4) = 149.
Mass of nitrogen in Ammonium Phosphate = 14*3 = 42.
Percentage of Nitrogen by Mass = 42/149 * 100 = 28.2 %

(c) (i) Ionic Equation for Neutralization is ALWAYS:
H(+) + OH(-) ---> H2O

(ii) Ammonium salts react with the hydroxides of the reactive metals (Ca, K, Na) to give off Ammonia.
Therefore, if we use Ammonium Nitrate, the reaction with CaOH will give off ammonia resulting in a loss of Nitrogen which is essential in fertilizers. This would not happen with Potassium Nitrate so it is the better choice.

(d) This is your usual test for Nitrate ions:
Add sodium hydroxide to the solution and then add aluminium foil and then heat the solution. If ammonia gas (gas which turns red litmus to blue) is given off then nitrate ions are present.

 

[irfan.kheerdali]

You didn't mention the subject. -_-
Still though, here's the answer:

(a) (i) Acid needs to be Hydrochloric Acid, HCl.
Alkali can be Potassium Hydroxide, KOH.
Reaction --> HCl + KOH ---> KCl + H2O.

(ii) We need to describe how to produce SOLID potassium chloride. So:
Titration is done since both the base and the salt are soluble. Acid (HCl) is slowly added to the Alkali (KOH) until the alkali is neutralized. Hence, we obtain a solution of the salt KCl. We will then evaporate the solution to obtain solid KCl crystals.

(b) (i) Ammonium ion = NH4 + , Phosphate ion = PO4 -3, therefore:
Ammonium Phosphate = (NH4)3PO4.

(ii) Mr of Ammonium Phosphate = (14*3) + (1*4*3) + (31*1) + (16*4) = 149.
Mass of nitrogen in Ammonium Phosphate = 14*3 = 42.
Percentage of Nitrogen by Mass = 42/149 * 100 = 28.2 %

(c) (i) Ionic Equation for Neutralization is ALWAYS:
H(+) + OH(-) ---> H2O

(ii) Ammonium salts react with the hydroxides of the reactive metals (Ca, K, Na) to give off Ammonia.
Therefore, if we use Ammonium Nitrate, the reaction with CaOH will give off ammonia resulting in a loss of Nitrogen which is essential in fertilizers. This would not happen with Potassium Nitrate so it is the better choice.

(d) This is your usual test for Nitrate ions:
Add sodium hydroxide to the solution and then add aluminium foil and then heat the solution. If ammonia gas (gas which turns red litmus to blue) is given off then nitrate ions are present.

thank you very much saad

 

[Saad Mughal]

thank you very much saad

No problem at all.

 

[irfan.kheerdali]

You didn't mention the subject. -_-
Still though, here's the answer:

(a) (i) Acid needs to be Hydrochloric Acid, HCl.
Alkali can be Potassium Hydroxide, KOH.
Reaction --> HCl + KOH ---> KCl + H2O.

(ii) We need to describe how to produce SOLID potassium chloride. So:
Titration is done since both the base and the salt are soluble. Acid (HCl) is slowly added to the Alkali (KOH) until the alkali is neutralized. Hence, we obtain a solution of the salt KCl. We will then evaporate the solution to obtain solid KCl crystals.

(b) (i) Ammonium ion = NH4 + , Phosphate ion = PO4 -3, therefore:
Ammonium Phosphate = (NH4)3PO4.

(ii) Mr of Ammonium Phosphate = (14*3) + (1*4*3) + (31*1) + (16*4) = 149.
Mass of nitrogen in Ammonium Phosphate = 14*3 = 42.
Percentage of Nitrogen by Mass = 42/149 * 100 = 28.2 %

(c) (i) Ionic Equation for Neutralization is ALWAYS:
H(+) + OH(-) ---> H2O

(ii) Ammonium salts react with the hydroxides of the reactive metals (Ca, K, Na) to give off Ammonia.
Therefore, if we use Ammonium Nitrate, the reaction with CaOH will give off ammonia resulting in a loss of Nitrogen which is essential in fertilizers. This would not happen with Potassium Nitrate so it is the better choice.

(d) This is your usual test for Nitrate ions:
Add sodium hydroxide to the solution and then add aluminium foil and then heat the solution. If ammonia gas (gas which turns red litmus to blue) is given off then nitrate ions are present.

plz can you give me easy understanding revision notes for chemistry and if possible biology

 

[Saad Mughal]

plz can you give me easy understanding revision notes for chemistry and if possible biology

https://www.xtremepapers.com/community/threads/o-level-notes-center.11138/
Press F3 and type 'Chemistry'.

 

[Deadly Orchid]

Physics question! Please if possible, solve this by drawing in the picture itself using MS paint or some other editing software, and then posting the solution here.

 

[Saad Mughal]

Physics question! Please if possible, solve this by drawing in the picture itself using MS paint or some other editing software, and then posting the solution here.

I'm horrible at paint but I hope you get the idea:



The red lines represent the NORMAL (90 deg.) to the Mirror. First of all draw the normal at the point where the incident ray strikes the mirror. Then measure the angle of incidence and draw the reflected line. Remember angle of incidence = angle of reflection. Do the same for the second light ray as well. The coloured angles represent equal angles.
The black dotted lines show the method for tracing back the image of P. Just trace back the reflected rays using dotted lines BEHIND the mirror and the intersection of the dotted lines is the image of P represent by P'.
To verify the image of P, you can use the distance method represented by the pink line. The distance of P from mirror = The distance of P' from mirror. This holds true for all plane mirrors.
P.S. The drawing is not accurate nor neat.