Physics, Chemistry and Biology: Post your doubts here!

[weirdoatlarge77]

HELP WITH CHEMISTRY QUESTION PLEASE

QUESTION 1C ( http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s12_qp_32.pdf )

Shouldnt nitrogen have high melting/boiling points because of their strong triple covalent bonding?

Confused

 

[Faaiz Haque]

Need help with chem question please.

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s05_qp_3.pdf

Question 3 A i and ii
How do we draw monomers and polymers.. can you tell the answer and explain please?

 

[Fatum Zuh]

I need help!
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s03_qp_3.pdf
Question 3[ii], [c] and [d][ii][iii]
Thanks

 

[Faaiz Haque]

HELP WITH CHEMISTRY QUESTION PLEASE

QUESTION 1C ( http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s12_qp_32.pdf )

Shouldnt nitrogen have high melting/boiling points because of their strong triple covalent bonding?

Confused

yeah but i'm guessing due to the weak intermolecular forces its mp/bp is very low, i guess it's an exception to its triple covalent bonding. Still unsure

 

[Faaiz Haque]

I need help!
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s03_qp_3.pdf
Question 3[ii], [c] and [d][ii][iii]
Thanks

D ii ) Propene because as you can see there's 3 C atoms.. and the structural formula is just a simple propene with 3 C atoms, 1 double bond , and 6 H atoms..
CH3—CH=CH2
D iii ) Landfill sites..forms methene, non bio -degradable
burning...forms posinous or toxic gases

There is no 3 C ii btw.

 

[ZaqZainab]

I need help!
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s03_qp_3.pdf
Question 3[ii], [c] and [d][ii][iii]
Thanks

3 ii chloro means chlorine and it is a photochemical reaction means it needs light you have to Learn it!!
c this are supposed to be learned DO YOU HAVE A TEXT BOOK?? well here are some notes might help
d i C3H6 is propene see how many carbons are there and Hydrogen in the drawing just add a double bond!
ii ATTACHMENT
FORGOT TO PUT THE n
iii polymers are just like plastics and sometimes even plastic so you know plastics are non biodegradable and burning them makes gases like Carbon monoxide which are toxic

 

[Jelleh Belleh]

View attachment 27177
So all these scores here are out of 200? Some of them seem unbelievable such as 158/200 for an A*. That basically means 79% is an A*, someone explain please

I was also really confused about the grade thresholds, especially after looking at the ones for chemistry. Last year, for one of them, you only needed a 131/180 to get an A*. Someone please explain!

 

[oahmed64]

i have a problem with the chemical reactions chapter
so when the get u a graph of a rate of reaction and they say sketch the graph of the same experiment using a more concentrated acid for example,when do we join the two graphs (same end volume of hydrogen for example) and when do we not?

 

[Sean123]

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

I have a doubt on making polymers and monomers. Help is needed

 

[ZaqZainab]

I was also really confused about the grade thresholds, especially after looking at the ones for chemistry. Last year, for one of them, you only needed a 131/180 to get an A*. Someone please explain!

because many people on earth are dumb including me
and if most of them get bad grades people would stop taking IGCSE and then you what happens!

 

[Princess Raven]

guys MAY JUNE 2011 V 31 CHEMISTRY P3 Q 5 PART B can someone explain y the third rxn isnt redox and y the first one is??? also q 6 same year y isnt butane first obtain by fractional distillation of petroleum and then by craking u get butene and then by adding steam we get butanol??? PLZZZ

 

[Timi Adeg]

because many people on earth are dumb including me
and if most of them get bad grades people would stop taking IGCSE and then you what happens!

Nah you're not dumb. Everyone is gifted

 

[Timi Adeg]

because many people on earth are dumb including me
and if most of them get bad grades people would stop taking IGCSE and then you what happens!

Don't say that. I'm guessing you don't like chemistry?

 

[Timi Adeg]

I was also really confused about the grade thresholds, especially after looking at the ones for chemistry. Last year, for one of them, you only needed a 131/180 to get an A*. Someone please explain!

Exactly !

 

[Jelleh Belleh]

It's weird though, because teachers have always told us we need grades like 90% to get A*s.. I guess not?
Anyway, chemistry definitely isn't my strongest subject either, I really hope the thresholds will be low this year as well. :3 Good luck everyone, A*s inshaAllah!

 

[ZaqZainab]

guys MAY JUNE 2011 V 31 CHEMISTRY P3 Q 5 PART B can someone explain y the third rxn isnt redox and y the first one is??? also q 6 same year y isnt butane first obtain by fractional distillation of petroleum and then by craking u get butene and then by adding steam we get butanol??? PLZZZ

5b i really don't know what the M.S is saying i would say because bound breaking takes place and that is exothermic Bounds break because electrons are lost so they split up then to become and atom electrons are gained
Wait can you provide a link http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s11_qp_32.pdf is it this one cause i don't see Question 5 haveing 3 equations

 

[semsemhosam]

I have a doubt on making polymers and monomers. Help is needed

POlymers are made from monomers (the small repeating units) ..
★Condensation polymerisation : small molecules are lost like water or OH when the monomers are joining together
★Addition polymerisation : polymers are formed due to rearrangement of bonds only WITHOUT losing any molecules

 

[GorgeousEyes]

Guys , Paper 1 physics has different variants ? or they have same questions ??

 

[Princess Raven]

5b i really don't know what the M.S is saying i would say because bound breaking takes place and that is exothermic Bounds break because electrons are lost so they split up then to become and atom electrons are gained
Wait can you provide a link http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s11_qp_32.pdf is it this one cause i don't see Question 5 haveing 3 equations

DUDE V 31!!!!

 

[Maro ashroof]

assalamu alaykom...
chemistry question:
can someone please explain for me how does a voltaic cell work and what are the differences between sacrificial protection and cathodic protection?
Thank you in advance