Biology; Chemistry; Physics: Post your doubts here!

[Saad Mughal]

thanks. by the way just wanted to confirm are the Fe3+ ions red in water, cuz i just read online that they are yellow?

I'm also not sure because I've read that it is yellow.

 

[usama321]

Apparatus is given so I'll just provide the procedure.
-Pour water on the cloth and wet it.
- Tie the cloth to the side of the beaker using the string.
- Place the thermometer in the beaker.
- As time passes, the reading on the thermometer decreases.
- The decrease in reading is because of evaporation which causes cooling (you guys know why).
Conclusion: When we sweat, our body is at high temperature, the sweat in normal conditions evaporates causing cooling and maintaining a constant body temperature.
Hope that helps.

but the reading should have decreased anyway, due to the difference in room temperature and that of beaker? Should we repeat the next time without using the wet cloth?

 

[Saad Mughal]

but the reading should have decreased anyway, due to the difference in room temperature and that of beaker? Should we repeat the next time without using the wet cloth?

The purpose of the experiment is to show that evaporation causes cooling, the reading would have slowly decreased anyway but we have to describe that in normal conditions our sweat evaporates and causes cooling. In humid conditions, we feel hot because the rate of evaporation is very slow, hence proving that evaporation is necessary for maintaining our body temperature.

 

[usama321]

Why not? When we draw ray diagrams of a converging lens, the image is formed on the point where the rays meet, and that image is inverted. No?

hmmmm guess that would produce an inverted one too

 

[Hskk]

hmmmm guess that would produce an inverted one too

So then both cases are correct. Let's just hope the examiner knows that.

 

[Hskk]

Is Carbon Monoxide produced in the electrolysis of aluminium oxide?

 

[Jassim]

Can anybody help me with these questions?
1. Describe double circulation in the human body.
2. Function of a sensory neuron.
3. State the characteristics and the role of the exchange surface of alveoli in gas exchange.
4. Describe removal of carbon dioxide from lungs. (4 marks)
Thanks

 

[Jassim]

Is Carbon Monoxide produced in the electrolysis of aluminium oxide?

No.

 

[Saad Mughal]

Is Carbon Monoxide produced in the electrolysis of aluminium oxide?

At the anode, oxygen gas forms, O2, which reacts with the anode to form Carbon Dioxide. Carbon Moxoide is not formed.

 

[Hskk]

Can anybody help me with these questions?
1. Describe double circulation in the human body.
2. Function of a sensory neuron.
3. State the characteristics and the role of the exchange surface of alveoli in gas exchange.
4. Describe removal of carbon dioxide from lungs. (4 marks)
Thanks

1. The blood flows from the body to the heart, then to the lungs and back to the heart again, which pumps its to the body. So in one cycle, the blood flows through the heart twice, that's double circulation.
2. It transmits the impulses received from the sensory organs to the CNS.
3. It has a one-cell thick membrane thus allowing minimum resistance during gaseous exchange. It is covered with a thin film of water that speeds up the diffusion of gases. It's in contact with a thick network of blood capillaries so a diffusion gradient is maintained allowing efficient gaseous exchange.
4. Air breathed in has less CO2 than the blood inside the body so a diffusion gradient is established and CO2 diffuses out from the blood into the air in the alveoli. A continuous flow of blood and those factors mentioned in point 3. ensure efficient gaseous exchange. Now air containing a higher conc. of CO2 is leaves the body when the diaphragm and external intercostal muscles relax and inter intercostal muscles contract decreasing the volume of the thoracic cavity which pushes the air out.
Best of luck

 

[Hskk]

At the anode, oxygen gas forms, O2, which reacts with the anode to form Carbon Dioxide. Carbon Moxoide is not formed.

Oh okay. Thank you.

 

[Jassim]

1. The blood flows from the body to the heart, then to the lungs and back to the heart again, which pumps its to the body. So in one cycle, the blood flows through the heart twice, that's double circulation.
2. It transmits the impulses received from the sensory organs to the CNS.
3. It has a one-cell thick membrane thus allowing minimum resistance during gaseous exchange. It is covered with a thin film of water that speeds up the diffusion of gases. It's in contact with a thick network of blood capillaries so a diffusion gradient is maintained allowing efficient gaseous exchange.
4. Air breathed in has less CO2 than the blood inside the body so a diffusion gradient is established and CO2 diffuses out from the blood into the air in the alveoli. A continuous flow of blood and those factors mentioned in point 3. ensure efficient gaseous exchange. Now air containing a higher conc. of CO2 is leaves the body when the diaphragm and external intercostal muscles relax and inter intercostal muscles contract decreasing the volume of the thoracic cavity which pushes the air out.
Best of luck

Thanks a lot Hskk, this was very helpful

 

[usama321]

Oh okay. Thank you.

well just confirmed, the image is formed on the retina, and not before it. For those who suffer from short sightedness, the image is formed before the retina. And those who suffer from far sightedness, it is formed at the back of the retina.

asma tareen

 

[chocolate_girl]

Hello people. Could someone tell me that in atps(of all 3 subjects) is it always necessary to draw graphs of best fit and that can we draw the line of best fit with free hand or ruler use is necessary.
Awaiting response......

 

[Hskk]

well just confirmed, the image is formed on the retina, and not before it. For those who suffer from short sightedness, the image is formed before the retina. And those who suffer from far sightedness, it is formed at the back of the retina.

Great. Now we can't even trust the marking schemes.

 

[chocolate_girl]

Please somebody briefly tell me the colour changes in oxidising and reducing agents in our syllabus. Thnks.......

 

[usama321]

why?

 

[usama321]

Hello people. Could someone tell me that in atps(of all 3 subjects) is it always necessary to draw graphs of best fit and that can we draw the line of best fit with free hand or ruler use is necessary.
Awaiting response......

actually the straight line of best fit must ALWAYS be drawn by a ruler. However, if it is a curve of best fit, you have to draw it by hand, don't draw it by ruler

 

[chocolate_girl]

actually the straight line of best fit must ALWAYS be drawn by a ruler. However, if it is a curve of best fit, you have to draw it by hand, don't draw it by ruler

Thankss and also do v have to always draw best fit line/curve although they have not mentioned it in question paper??

 

[usama321]

Thankss and also do v have to always draw best fit line/curve although they have not mentioned it in question paper??

i think they do mention it. By the way, whenever they say draw a line, if the points are not falling in line, then of course you have to draw a line of best fit, the same applies for curves too. Don't go out of the way of your line or curve to include a point in it.