Physics, Chemistry and Biology: Post your doubts here!

[My Name]

Biology mcq.
The small intestines of cows are similar in general structure and function to the small intestines of
humans.
A disease in cows reduces the number of villi in their small intestines.
The cows lose weight and become weak.
What explains this?
A less amylase produced
B less peristalsis
C slower absorption of nutrients
D slower digestion of proteins

The answer is C.
The villi in the small intestine provide large surface area for faster diffusion..so when they are destroyed it results in slower absorption of nutrients.

Thankyou.
It is May/June 2014

Welcome
Ohkay

 

[zahra azam]

Biology mcq.
The small intestines of cows are similar in general structure and function to the small intestines of
humans.
A disease in cows reduces the number of villi in their small intestines.
The cows lose weight and become weak.
What explains this?
A less amylase produced
B less peristalsis
C slower absorption of nutrients
D slower digestion of proteins

Its slower absorption of nutrients.
Cuz the surface area for absorption is reduced

 

[Ushnaaa]

The answer is C.
The villi in the small intestine provide large surface area for faster diffusion..so when they are destroyed it results in slower absorption of nutrients.

Welcome
Ohkay

Thanks again.

 

[My Name]

Thanks again.

Welcome!

 

[Ushnaaa]

Its slower absorption of nutrients.
Cuz the surface area for absorption is reduced

Thankyou zahra.

 

[zahra azam]

Thankyou zahra.

Hehe my pleasure

 

[Muaaz Iqbal]

Anyone's having Physics Study guide ?

 

[Ushnaaa]

Anyone's having Physics Study guide ?

I have it,but its not letting me upload

 

[SM.Farrukh K. Jafri]

Salam,I need some help in chemistry,my Igcse just started last month btw ,please tell me whats chromatography/fractional distillation/subblimation keeping in mind that I'm a new IGCSE student.Thanks alot

 

[qwertypoiu]

Salam,I need some help in chemistry,my Igcse just started last month btw ,please tell me whats chromatography/fractional distillation/subblimation keeping in mind that I'm a new IGCSE student.Thanks alot

Chromatography is a method of separating a mixture. It's usually done for separating dyes. To do it, take a filter paper, and add a drop of the mixture on it. Place the filter paper into a beaker of water so that a part of the paper is dipped in water, but the drop of mixture isn't. Water will naturally soak through the paper. When it comes in contact with the mixture, based on solubility of the constituents, the mixture will separate.

In many cases, we want to compare various mixtures to see if they have any common constituents between them. To do that, you need to take a filter paper, draw a horizontal pencil line on it (pencil because the graphite "lead" doesn't dissolve in water) and put a dot for each mixture side by side. The paper should be then dipped into a beaker of water (only the part lower than the pencil line should be in contact with water!). Water will naturally soak the paper, moving upwards. When it meets the mixtures, they will separate as mentioned before. If the mixtures being compared contain one or more of the same constituents, they can be identified by seeing if they moved up the paper the same distance.

In this picture, you can see that the two mixtures both contained the blue and the green parts, but each had a separate substance of their own.


Fractional distillation is another method of separation. This one's usually done on a mixture of liquids each with different boiling points. The idea is to steadily heat and increase the temperature of the mixture, so that each liquid can separately boil and be led somewhere, where they are condensed and removed. This way all the liquids may be extracted.




Sublimation is simply the conversation of solid to gas directly by heating. Normally we'd expect it to turn to liquid first, but for reasons you will find out later, some substances directly turn to gas instead. An example is iodine, which is a grey-black solid, that sublimates upon heating to form purple vapour.




In this picture, iodine solid is heated to form gas, which is then cooled down using a test tube of ice, causing it to "freeze" back into solid.

Homework question: what's gas to solid change called? (the one I referred to as "freeze")

 

[SM.Farrukh K. Jafri]

Chromatography is a method of separating a mixture. It's usually done for separating dyes. To do it, take a filter paper, and add a drop of the mixture on it. Place the filter paper into a beaker of water so that a part of the paper is dipped in water, but the drop of mixture isn't. Water will naturally soak through the paper. When it comes in contact with the mixture, based on solubility of the constituents, the mixture will separate.
View attachment 57141
In many cases, we want to compare various mixtures to see if they have any common constituents between them. To do that, you need to take a filter paper, draw a horizontal pencil line on it (pencil because the graphite "lead" doesn't dissolve in water) and put a dot for each mixture side by side. The paper should be then dipped into a beaker of water (only the part lower than the pencil line should be in contact with water!). Water will naturally soak the paper, moving upwards. When it meets the mixtures, they will separate as mentioned before. If the mixtures being compared contain one or more of the same constituents, they can be identified by seeing if they moved up the paper the same distance.
View attachment 57142
In this picture, you can see that the two mixtures both contained the blue and the green parts, but each had a separate substance of their own.


Fractional distillation is another method of separation. This one's usually done on a mixture of liquids each with different boiling points. The idea is to steadily heat and increase the temperature of the mixture, so that each liquid can separately boil and be led somewhere, where they are condensed and removed. This way all the liquids may be extracted.

View attachment 57144


Sublimation is simply the conversation of solid to gas directly by heating. Normally we'd expect it to turn to liquid first, but for reasons you will find out later, some substances directly turn to gas instead. An example is iodine, which is a grey-black solid, that sublimates upon heating to form purple vapour.

View attachment 57145


In this picture, iodine solid is heated to form gas, which is then cooled down using a test tube of ice, causing it to "freeze" back into solid.

Homework question: what's gas to solid change called? (the one I referred to as "freeze")

Thanks alot man JazakAllahuKhairan

 

[ahmed faraz]

Can anyone explain me this question.

ANY HELP WILL BE HIGHLY APPERICIATED!

THANKS IN ADVANCE!

 

[My Name]

Can anyone explain me this question.

ANY HELP WILL BE HIGHLY APPERICIATED!

THANKS IN ADVANCE!

The question asks about the advantage of transmitting electricity at a high voltage.
The thing is that high voltages improve efficiency by reducing heat loss in the power cables.This basically means that less energy is lost.

So the answer will be C.

 

[ahmed faraz]

The question asks about the advantage of transmitting electricity at a high voltage.
The thing is that high voltages improve efficiency by reducing heat loss in the power cables.This basically means that less energy is lost.

So the answer will be C.

Thanks for your reply.
on the other hand,high voltage could speed up current so that electricity might be transmitted faster. (As voltage is the one pushing the current).

 

[malikk]

hey . ive just started chemistry and bio and physics can anyone please give me some notes to make it easy for me to study them.

 

[Maie Ihab]

are there any question on biology igcse classified question
if yes please, can anyone supply me with the link

 

[My Name]

hey . ive just started chemistry and bio and physics can anyone please give me some notes to make it easy for me to study them.

Here and here are links to notes thread,I'm not sure if all the links are working.Just choose what you like and download.
I hope that helps.

 

[My Name]

are there any question on biology igcse classified question
if yes please, can anyone supply me with the link

You can check some posts on this thread.

 

[Ushnaaa]

Anyone studied from Biology D.G.Mackean?

 

[Ushnaaa]

Anyone studied from Biology D.G.Mackean?