• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

Any Type of Doubts in ENg Phy Chem Bio or Math....Ask me here!!!

xoxoxogaurav123

xoxoxogaurav123

Messages
59
Reaction score
8
Points
18
Van der Waals' forces include all intermolecular forces that act between electrically neutral molecules. Several special cases occur.
Permanent forces occur when the interacting molecules contain groups or regions that are permanently electron-rich or electron poor. For example, the animation at right shows short range forces acting between molecules of gaseous HCl. The electron-rich region (on the chlorine atom) is colored red; the electron-poor hydrogen atom is shown in blue. Notice that the molecules align when they pass close to each other because the positive end of one molecule is attracted to the negative end of the other. The yellow glow indicates the formation of a weak intermolecular attraction during a close encounter. Notice that a molecule's momentum is often strong enough to overcome the attraction and prevent it from being captured in a cluster of other molecules.
When the the molecule has a distinctly positive end and a negative end, the permanent force is referred to as a dipole-dipole attraction. Weaker (but still noticeable) permanent forces can act between any molecules with polar bonds. For example, the oxygen atoms in CO2 are electron-rich, while the carbon atom in the center is electron poor, so the oxygen atom of one CO2 can be attracted to the carbon of another during very close encounters.
Hydrogen bonds are abnormally strong dipole-dipole attractions that involve molecules with -OH, -NH, or FH groups. Hydrogen atoms are very small (with an atomic radius of about 37 pm, they're smaller than any other atom but helium). When a bonded electronegative atom (oxygen, nitrogen, or fluorine) pulls electrons away from the hydrogen atom, the positive charge that results is tightly concentrated. The hydrogen is intensely attracted to small, electron-rich O, N, and F atoms on other molecules. (Larger electron-rich groups and atoms (like -Cl, for example) will also attract the hydrogen, but because their electrons aren't as tightly concentrated, the resulting dipole-dipole attraction is too weak to be considered a "real" hydrogen bond.) Hydrogen bonds are essential for building biological systems: they're strong enough to bind biomolecules together but weak enough to be broken, when necessary, at the temperatures that typically exist inside living cells.
 
geminisign

geminisign

Messages
19
Reaction score
6
Points
13
F

Fatima18

Messages
558
Reaction score
114
Points
53
Hi guys.Please clear out these doubts.
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Mathematics (0580)/0580_s11_qp_42.pdf
number 8a)
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Mathematics (0580)/0580_w11_qp_42.pdf
3biii), 7d, ei, eii, fi fii
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Mathematics (0580)/0580_w11_qp_43.pdf
3b), 6bii), 11bii)
http://olevel.sourceforge.net/papers/0580/0580_s12_qp_41.pdf
4di and ii), e), 8b and eiii), 6bii)
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Mathematics (0580)/0580_s11_qp_43.pdf
11iv and v)
 
Tanvi Shah

Tanvi Shah

Messages
62
Reaction score
54
Points
18
Fatima18 said:
Hi guys.Please clear out these doubts.
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Mathematics (0580)/0580_s11_qp_42.pdf
number 8a)
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Mathematics (0580)/0580_w11_qp_42.pdf
3biii), 7d, ei, eii, fi fii
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Mathematics (0580)/0580_w11_qp_43.pdf
3b), 6bii), 11bii)
http://olevel.sourceforge.net/papers/0580/0580_s12_qp_41.pdf
4di and ii), e), 8b and eiii), 6bii)
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Mathematics (0580)/0580_s11_qp_43.pdf
11iv and v)
Click to expand...
Hi, Fatima18.......... attached is a zip folder which contains pictures of the solution to your doubts... Hope my handwriting is legible enough.. ;) like my post and follow me if you think I helped.. ;)
 

Attachments

  • xtreme.rar
    977 KB · Views: 9
Tanvi Shah

Tanvi Shah

Messages
62
Reaction score
54
Points
18
somya said:
help me out plz!!
1. if it takes 6 men 4 days to dig a hole 3 ft deep, how long will it take 10 men to dig a hole 7 ft deep??

2. a floor is covered by 800 tiles measuring 10 cm square. how many square tiles of side 8 cm would be needed to cover the same floor??
Click to expand...
Hi Somya,
here is the solution to your first doubt (attached picture)... well I know many members have helped enough already.. but still I'd like to do my part
always remember when there are questions like these, it is always men*days OR in general people*time
Hope I helped.. :)
 

Attachments

  • May0543.jpg
    May0543.jpg
    70.5 KB · Views: 11
Prathmesh Thakkar

Prathmesh Thakkar

Messages
355
Reaction score
160
Points
53
geminisign said:
No I don't so, not sure what that is aha...
I've got another question
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_s09_qp_3.pdf

Question 11b,
What is the direction of the electric field in order to cancel out the deflection of the alpha-particles?

Can you help me? I don't really understand what the fields mean.
Click to expand...
Perpendicular out of the page....the opp direction of that of the magnetic field..
Electric/Magnetic field is a region in which charge/magnetic material feels a force......
 
Prathmesh Thakkar

Prathmesh Thakkar

Messages
355
Reaction score
160
Points
53
xoxoxogaurav123 said:
Van der Waals' forces include all intermolecular forces that act between electrically neutral molecules. Several special cases occur.
Permanent forces occur when the interacting molecules contain groups or regions that are permanently electron-rich or electron poor. For example, the animation at right shows short range forces acting between molecules of gaseous HCl. The electron-rich region (on the chlorine atom) is colored red; the electron-poor hydrogen atom is shown in blue. Notice that the molecules align when they pass close to each other because the positive end of one molecule is attracted to the negative end of the other. The yellow glow indicates the formation of a weak intermolecular attraction during a close encounter. Notice that a molecule's momentum is often strong enough to overcome the attraction and prevent it from being captured in a cluster of other molecules.
When the the molecule has a distinctly positive end and a negative end, the permanent force is referred to as a dipole-dipole attraction. Weaker (but still noticeable) permanent forces can act between any molecules with polar bonds. For example, the oxygen atoms in CO2 are electron-rich, while the carbon atom in the center is electron poor, so the oxygen atom of one CO2 can be attracted to the carbon of another during very close encounters.
Hydrogen bonds are abnormally strong dipole-dipole attractions that involve molecules with -OH, -NH, or FH groups. Hydrogen atoms are very small (with an atomic radius of about 37 pm, they're smaller than any other atom but helium). When a bonded electronegative atom (oxygen, nitrogen, or fluorine) pulls electrons away from the hydrogen atom, the positive charge that results is tightly concentrated. The hydrogen is intensely attracted to small, electron-rich O, N, and F atoms on other molecules. (Larger electron-rich groups and atoms (like -Cl, for example) will also attract the hydrogen, but because their electrons aren't as tightly concentrated, the resulting dipole-dipole attraction is too weak to be considered a "real" hydrogen bond.) Hydrogen bonds are essential for building biological systems: they're strong enough to bind biomolecules together but weak enough to be broken, when necessary, at the temperatures that typically exist inside living cells.
Click to expand...
:p Intermolecular forces likh sedhe se......
 
You must log in or register to reply here.
Top