Biology; Chemistry; Physics: Post your doubts here!

[Jenn]

What is the difference between an onion cell and a typical plant cell?

 

[KyleoAhsan]

What is the difference between an onion cell and a typical plant cell?

Well Onion Cells don't have Chloroplasts because they grow underground! so they don't photosynthesize! Plant Cells have Chloroplasts to absorb sunlight...onion cells are found in tubers! That's pretty much all I know I guess one difference !

 

[danial 234]

Re: Biology,Chemistry & Physics Help Available Here !

scouserlfc .. great idea !! :Yahoo!:
However Mods, sticky this topic, would you ? [/quote
can i give combined sciences(phy,chem)

 

[Tuba noor]

design an experiment to show how rate of cooling can be reduced for boiling water .

design an experiment to demonstrate random motion of molecules in liquids .

 

[scouserlfc]

design an experiment to show how rate of cooling can be reduced for boiling water .

design an experiment to demonstrate random motion of molecules in liquids .

these are pretty easy and u can find answers in Atps as well for the first one u need lagging material on one beaker and compare with another without lagging and write the experiment like u do in ATP s !

for the second one u can do plenty of stuff,i remember this one put pollen grains in water and u will see pollen grains moving in a random pattern showing that water molecules moving randomly colliding with pollen grains

this is just brief i can explain further if u want ?

 

[smart_boy]

I am uploading the recent Jun 2012 IGCSE 0625 Phyiscs paper 32. Can you please solve question 9b in it and then explain it to me too..??? Cos i m getting really confused..!!! Thanks..

 

[scouserlfc]

^ wait i will solve it soon tomorrow or later if no one solve have no time atm sorry

 

[scouserlfc]

can any body tell that

concentration of
Glucose , Urea , Water , Salt is ..High or Low ?

concentration in what ???????????????

 

[KyleoAhsan]

I mean to say that ...is the concentration of Glucose , Urea , Water , Salt..higher in Blood or Dylasis fluid ?

Concentration of Glucose, dissolved mineral ions and salts will be same in dialysis fluid and blood, This is because if a concentration gradient is built, the dissolved ions, glucose and salts will diffuse out and useful substances will be filtered out of the blood! The whole use of dialysis is to mimic the kidneys, which removes urea and other harmful substances, In dialysis fluid the concentration of these substances will be low, thus urea and other harmful substances diffuse in to the dialysis fluid,

So, Concentration of Urea is higher in blood than dialysis fluid! As for water I think it would be same! though I am not sure

 

[scouserlfc]

I am uploading the recent Jun 2012 IGCSE 0625 Phyiscs paper 32. Can you please solve question 9b in it and then explain it to me too..??? Cos i m getting really confused..!!! Thanks..

Sorry for late reply,and i know its really late

BTW the question is pretty easy and more like a math question if u will allow me to say
so first we need to know the resistance of each lamp at 0.9A which is 5% more of its original resistance !
5% * 8 =0.4
now the actual resistance of the lamp at 0.9A is 8.4 ohms

Now for finding out how many lamps would be required to fail short we use V=IR equation and we know two things that voltage reamains 240 volts and the current is 0.9 A in each lamp
V=IR
240=0.9 * 8.4 (where n is the no. of lamps which are still working and give the 0.9A current reading )
so n= 31.7
as the thing says maximum no. of lamps rounding of 31.7 to nearest whole no. makes it 32 so 32 lamps in reality are working

Now for finding how many lamps have failed its simple we use the total lamps - the working lamps
40-32=8
So 8 lamps fail

and still confused abt the question and want to check MS then go to this link
http://www.xtremepapers.com/communi...apers-marking-schemes-grade-thresholds.18863/
Credit goes to captain danger for all this so dont thank me for this link

 

[smart_boy]

Sorry for late reply,and i know its really late

BTW the question is pretty easy and more like a math question if u will allow me to say
so first we need to know the resistance of each lamp at 0.9A which is 5% more of its original resistance !
5% * 8 =0.4
now the actual resistance of the lamp at 0.9A is 8.4 ohms

Now for finding out how many lamps would be required to fail short we use V=IR equation and we know two things that voltage reamains 240 volts and the current is 0.9 A in each lamp
V=IR
240=0.9 * 8.4 (where n is the no. of lamps which are still working and give the 0.9A current reading )
so n= 31.7
as the thing says maximum no. of lamps rounding of 31.7 to nearest whole no. makes it 32 so 32 lamps in reality are working

Now for finding how many lamps have failed its simple we use the total lamps - the working lamps
40-32=8
So 8 lamps fail

and still confused abt the question and want to check MS then go to this link
http://www.xtremepapers.com/communi...apers-marking-schemes-grade-thresholds.18863/
Credit goes to captain danger for all this so dont thank me for this link

Thanks a lot...!!!!

 

[scouserlfc]

Thanks a lot...!!!!

Not a problem

 

[smart_boy]

Not a problem

I need to ask you one more thing:
Why is it that Malaria is common in many parts of the world where the sickle cell allele is present in the population?

 

[scouserlfc]

I need to ask you one more thing:
Why is it that Malaria is common in many parts of the world where the sickle cell allele is present in the population?

shudnt your question be why it is less common in these areas rather than more common if its more common than ive got the answer to ur present question Why is it that Malaria is common in many parts of the world where the sickle cell allele is present in the population? this is becuz if u look at how these people have blood cells which are half moon shaped then it makes these people more prone to death by Malaria as the virus can destroy their cells more easily and the ones that are normal if killed can cause that guy to get severe breathlessness and probably death,i dont really get the concept of resistance from Malaria if u have sickle cell anaemia read the article below if u too are confused
http://www.sicklecell.md/faq.asp

 

[incognitive lass]

write the following in chemical formula and mention the number of atoms.
1) calcium hydroxide
2) copper (II) sulphate.
3)1r0n (III) sulphate
4) ammonium chloride.

 

[scouserlfc]

write the following in chemical formula and mention the number of atoms.
1) calcium hydroxide
2) copper (II) sulphate.
3)1r0n (III) sulphate
4) ammonium chloride.

What do u mean by number of atoms i am thinking that u meant the oxidation state
1. Ca(OH)2 Ca has a charge of 2+ while (OH) has a charge of -1 so therefore we require 2 of these (OH)

2. CuSO4 Cu has a charge of +2 while SO4 has a charge of -2 so we dont do anything

3. FeSO4 Fe has a charge of +2 while SO4 has a charge of -2 so we dont do anything either

4. NH4Cl NH4 has a charge of +1 while Cl has a charge of -1 so again its all cool

Please make ur question further clear if this wasnt what u were looking for

 

[Anuja L. Nilaweera]

Please someone tell me,
How can we balance an equation, you'll take an example and explain me?
Please..........................

 

[Anuja L. Nilaweera]

anyone plz show me how to create a balancedequation and explain it too plz

Give me an example then I can explain it to you.

 

[Anuja L. Nilaweera]

Concentration of Glucose, dissolved mineral ions and salts will be same in dialysis fluid and blood, This is because if a concentration gradient is built, the dissolved ions, glucose and salts will diffuse out and useful substances will be filtered out of the blood! The whole use of dialysis is to mimic the kidneys, which removes urea and other harmful substances, In dialysis fluid the concentration of these substances will be low, thus urea and other harmful substances diffuse in to the dialysis fluid,

So, Concentration of Urea is higher in blood than dialysis fluid! As for water I think it would be same! though I am not sure

So what is the fluid that is in kidneys, which clears the urine?

 

[Vidushi Kaushali]

Please someone tell me,
How can we balance an equation, you'll take an example and explain me?
Please..........................

OK , you really caught me with something I always take time to do.

When you are balancing an equation , there is a certain order that you should follow.You should balance the Oxygen and the hydrogen at last bcz they are the ones which are difficult to balance. You can balance the other atoms before That.

If you take Al(OH)3 + HNO3 -----> Al(NO3)3 + H2O

You can see that the Al is already balanced. Then you move on to the nitrogen , you can see that on the left hand side there is only one N while on the right there are 3 , so you put 3 in front of HNO3. Then you move on to the hydrogen. You can see that of L.H.S. there are 6 , while on the right there are only 2 , so you put 3 in fron of H2O to balance it. Finally when you start to balance the Oxygen , you can see that there is no need to do it , since its already balanced.

This is the final equation

Al(OH)3 + 3HNO3 -----> Al(NO3)3 + 3H2O