Physics, Chemistry and Biology: Post your doubts here!

[franklin2012]

come on any one online please help its very urgent

 

[smart_boy]

anyone please help me now if u online please reply

Can you specify what exactly is your doubt in Q. 7 in that paper..?

 

[Reema]

Same here im havin a trouble with moments! which is da stable neutral and unstable equilibrium! pl reply me soon!
thank u

 

[Anuja L. Nilaweera]

Chemistry problem............................
Describe and explain evidence for the movement of particles in liquids and gases.
(the treatment of Brownian is not required)

 

[Anuja L. Nilaweera]

Another Chemistry problem........................
Explain everyday effects of diffusion in terms of particles, e.g. the spread of perfumes and cooking aromas; tea and coffee grains in water.

 

[Anuja L. Nilaweera]

Chemistry problem once again................................
State qualitatively the effect of molecular mass on the rate of diffusion and explain the dependence of rate of diffusion on temperature.

 

[smart_boy]

Chemistry problem............................
Describe and explain evidence for the movement of particles in liquids and gases.
(the treatment of Brownian is not required)

Diffusion is the process by which gases or liquids may mix as a result of the random motion of their particles. A common examples is, as you mentioned, the spread of perfumes and cooking aromas. In this case particles will have to leave the perfume bottle and spread out through the air, otherwise you wont be able smell them. As the kinetic theory says that all matter is made up of tiny, moving particles, invisible to the naked eye, diffusion is the evidence for moving particles: it proves that particles are constantly moving.
Rate of diffusion means how fast something diffuses. If you heat up the substance that is diffusing, its temperature will increase. This temperature rise is because the particles of the substance have been provided with more energy and they are moving faster than before. This faster movement will allow these particles to mix and spread out faster. Thus rate of diffusion increases, that means it is faster. The opposite happens when you cool the substance: diffusion slows down.
The Kinetic theory also states that particles that are heavier tend to move more slowly that lighter ones. Molecular mass basically means how heavy a particle is. An excellent example is when two pieces of cotton are placed at two ends of a closed glass tube. One has been dipped in conc hydrochloric acid, the other in ammonia solution. Within seconds a white smoke can be observed forming inside the tube, not in the centre but more towards the cotton dipped in acid. The reasoning for this is that particles of both chemicals diffused from the cotton through the tube and when they mixed and reacted, the white smoke of ammoium chloride formed. As ammonia particles are lighter than acid particles, they difused faster and reacted with the slowly diffusing particles.

 

[Anuja L. Nilaweera]

Diffusion is the process by which gases or liquids may mix as a result of the random motion of their particles. A common examples is, as you mentioned, the spread of perfumes and cooking aromas. In this case particles will have to leave the perfume bottle and spread out through the air, otherwise you wont be able smell them. As the kinetic theory says that all matter is made up of tiny, moving particles, invisible to the naked eye, diffusion is the evidence for moving particles: it proves that particles are constantly moving.
Rate of diffusion means how fast something diffuses. If you heat up the substance that is diffusing, its temperature will increase. This temperature rise is because the particles of the substance have been provided with more energy and they are moving faster than before. This faster movement will allow these particles to mix and spread out faster. Thus rate of diffusion increases, that means it is faster. The opposite happens when you cool the substance: diffusion slows down.
The Kinetic theory also states that particles that are heavier tend to move more slowly that lighter ones. Molecular mass basically means how heavy a particle is. An excellent example is when two pieces of cotton are placed at two ends of a closed glass tube. One has been dipped in conc hydrochloric acid, the other in ammonia solution. Within seconds a white smoke can be observed forming inside the tube, not in the centre but more towards the cotton dipped in acid. The reasoning for this is that particles of both chemicals diffused from the cotton through the tube and when they mixed and reacted, the white smoke of ammoium chloride formed. As ammonia particles are lighter than acid particles, they difused faster and reacted with the slowly diffusing particles.
View attachment 15090

Thank you..................................
But this question was not in an IGSCE book, it wad in a GCE book.

 

[AYEFABOOD]

An excellent and highly qualified biology teacher helps you to get A* in biology 0544431007

 

[Anuja L. Nilaweera]

An excellent and highly qualified biology teacher helps you to get A* in biology 0544431007

In whats country is she/he?

 

[AYEFABOOD]

Jeddah Saudi arabia

 

[sweetiepie]

http://www.xtremepapers.com/community/threads/useful-stuff-compiled.10273/ MORE NOTES ADDED HOPE THIS HELPS YOU ALL

 

[smart_boy]

Assalam-o-Alaikum.
Post your Physics, Chemistry and Biology doubts in here and members, along with me will try there best to help you out.

Can you please help me out with the following questions? I need the ans urgently as I hav my exam tomo... Thanks..
Q1. Explain the role of Penicillium in the production of penicillin.
Q2. Before Penicillium or the medium is put into the fermenter, it is cleaned with hot steam.
(a) Suggest why this is necessary.
(b) Suggest why the air supply to the fermenter comes into the base of it rather than the top
(c) Explain why it is important that carbon dioxide is allowed to escape from the fermenter.
Q3. Suggest 2 similarities and 1 difference between the conditions required in a fermenter used for making enzymes for biological washing powders and one used for making penicillin.

 

[semsemhosam]

Can you please help me out with the following questions? I need the ans urgently as I hav my exam tomo... Thanks..
Q1. Explain the role of Penicillium in the production of penicillin.
Q2. Before Penicillium or the medium is put into the fermenter, it is cleaned with hot steam.
(a) Suggest why this is necessary.
(b) Suggest why the air supply to the fermenter comes into the base of it rather than the top
(c) Explain why it is important that carbon dioxide is allowed to escape from the fermenter.
Q3. Suggest 2 similarities and 1 difference between the conditions required in a fermenter used for making enzymes for biological washing powders and one used for making penicillin.

which year nd session ?? pls give me the link and srry for the late reply i didnt have access to the internet since a very long time

 

[i-copeland]

Bio

Do they give you zero for a question if you answer it with some right things, but then also some wrong things?

Thanks

 

[somya]

Bio

Do they give you zero for a question if you answer it with some right things, but then also some wrong things?

Thanks

well, that depends on how many marks is the question for...
cause if its a one- mark question you have no chance, but for a for to five mark question, there is still some hope...!

 

[i-copeland]

well, that depends on how many marks is the question for...
cause if its a one- mark question you have no chance, but for a for to five mark question, there is still some hope...!

Like for example if its out of 5 and 3 i know and i make up other two (but they are wrong), will they still give me 3/5?

 

[somya]

Like for example if its out of 5 and 3 i know and i make up other two (but they are wrong), will they still give me 3/5?

yes..!
but they've gotta be correct..!

 

[i-copeland]

yes..!
but they've gotta be correct..!

What if I give 3 made up wrong ones and 3 right ones, and its out of 5 only?

 

[somya]

What if I give 3 made up wrong ones and 3 right ones, and its out of 5 only?

if your right ones are pretty accurate the you stand a chance of getting 3, but if your correct points are not that good then you score a 2!