Biology; Chemistry; Physics: Post your doubts here!

[shehri]

can someone plz give a link or something for coloured compounds in chemistry

http://olevelspreparation.blogspot.com/2012/05/all-colors-of-elements-in-chemistry.html

 

[Snowysangel]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Biology (5090)/5090_s07_qp_6.pdf
plz explain me Q1 (d)

You tie the piece of cloth to the mouth of the beaker, securing it with the threads. Measure the temperature at regular intervals. Then, take another such cloth and dampen it using water from the tap. At the same intervals as in the previous experiment, take the thermometer reading. Compare the two experiments and rate of heat loss. The beaker with the damp cloth will have a faster heat loss, as the moisture in it absorbs heat from the water and loses it to the surrounding as latent heat of evaporation, same as sweating does

 

[Hskk]

Thankyou and can u also explain me the topic surface area to volume ratio pleasee

Surface area increases when volume decreases. See, if you have one big potato and want to colour it by placing it in solution of dye, it will take alot of time for the potato to completely soak the dye, and probably, it'll still be uncoloured from the centre. But if you cut the same potato into small pieces, the time for the absorption of the dye decreases. This phenomena applies in the root hair cells, and villi in the intestine, where the finger like extensions increase surface area to volume ratio so that absorption of substances is maximised.

 

[HDIWAN]

Why did you multiply it by 0.3 and 0.5 together? ??

look closely at the question it says (0.5 Io) and Io=o.3

 

[chocolate_girl]

Can someone please post the best atp notes for phy chem n bio. Like last minute revision brief notes.

 

[TheStallion-Reborn]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_w11_qp_41.pdf question1 part b , subpart 1, I wrote, more margin of error. and the mark scheme says http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_w11_ms_41.pdf....should I have any hope on such deviations?/

 

[Saad Mughal]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_w11_qp_41.pdf question1 part b , subpart 1, I wrote, more margin of error. and the mark scheme says http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_w11_ms_41.pdf....should I have any hope on such deviations?/

The more the readings/repetitions, the more accurate the experiment!

 

[TheStallion-Reborn]

The more the readings/repetitions, the more accurate the experiment!

will i get marks for what i wrote?

 

[Saad Mughal]

will i get marks for what i wrote?

It's one mark. I don't think you'll get it.

 

[tweetie]

BIOLOGY Can someone help me please
There is a question in OCT/NOV 2005 Paper 6
Suggest how you would observe the yeast cells and how you would estimate their total population in the flask?
i looked it up in the marking scheme but still i don't understand the answer :'(

did u get the answer? cux i m stuck at the same question :/

 

[chocolate_girl]

any body tell me when exosmosis occurs in plant..???

When water leaves out of a plant cell, it is called exosmosis (tip to remember:exit from ex) when the plant cells are kept in a region of low water potential the water in them leaves by osmosis called exosmosis. The cell becomes flaccid. We say that it has plasmolysed.

 

[Ahmed Raja]

There is question in 5070/41/ON12, Q9 The student titrates R, an aqueous solution containing 7g/dm3 of organic acid with S an aqueous solution containing 0.100mol/dm3 of NaOH. Part E says calculate number of moles of acid in 1.00 dm3 of R. Plz tell me how to solve it. Its urgent plz

 

[papajohn]

There is question in 5070/41/ON12, Q9 The student titrates R, an aqueous solution containing 7g/dm3 of organic acid with S an aqueous solution containing 0.100mol/dm3 of NaOH. Part E says calculate number of moles of acid in 1.00 dm3 or R. Plz tell me how to solve it. Its urgent plz

1 dm3 contain 7g of organic acid. If u know this then you will simpy calculate by the Mole formulae.

 

[chocolate_girl]

http://papers.xtremepapers.com/CIE/...al O Level/Chemistry (5070)/5070_s09_qp_4.pdf
Someone please tell me the answer for question 2 part b-ii) with explanation.

 

[Suchal Riaz]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_w11_qp_41.pdf question1 part b , subpart 1, I wrote, more margin of error. and the mark scheme says http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_w11_ms_41.pdf....should I have any hope on such deviations?/

after some time the time of each complete swing will start to slow down ur results will be affected. u wont get any marks sorry.

 

[Suchal Riaz]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s09_qp_4.pdf
Someone please tell me the answer for question 2 part b-ii) with explanation.

the moltem lead bromide will solidify so there will be ions to carry current. therefore the lamp will be switched off.

 

[Ahmed Raja]

1 dm3 contain 7g of organic acid. If u know this then you will simpy calculate by the Mole formulae.

which mole formula? i do it with ratio's, can you tell me the formula?

 

[asma tareen]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Biology (5090)/5090_w10_qp_62.pdf
Q3ai) why is test tube C alkaline

 

[Ishaq]

Guys How to obtain Bigger or better crystals when preparing salts?

 

[asma tareen]

allow them to cool slowly with frezzer or anything else

Guys How to obtain Bigger or better crystals when preparing salts?