The Official Cricketweb Science Thread!

[Quaggas]

Q:

If mathematics is so good at describing the world, why has England gone up one place in the new FIFA rankings?

They managed two goals against Germany. Do that and your ranking's bound to increase.

[silentstriker]

Griffiths, I'm in 1st year (technically)... Jackson is the honours-year text at my uni.

So yeah, trying Jackson at my level would be an exercise in, er, pain.

Ah EM...one of my favorite physics topics . You'll have fun.

Maxwell was THE MAN.

[silentstriker]

Someone explain the universe to me in haiku form.

Go!

Not mine:

Timeless energy,
all dressed up, no place to go:
had to create space.

[vcs]

Ah EM...one of my favorite physics topics . You'll have fun.

Maxwell was THE MAN.

Indirectly led to the discovery of special relativity.

[Flem274*]

I'd just like to say I hate science for this chemistry assignment. The earth is flat and God did it.

Should probably grab the homework thread, but cbf. Wtf is this question asking me to do?

Use the molecules you have constructed (out of wine gums and tooth picks ftw) and test a single, double and triple bond to see if you can rotate the atoms on either side of the bond with respect to each other.

Which bond allows free rotation between the atoms joined?
Which bonds do not allow free rotation between the atoms joined?

What does it mean by rotation? Of course I can rotate them, they're lollies.

And yes, I know it's straightforward for you lot.

[silentstriker]

I'd just like to say I hate science for this chemistry assignment. The earth is flat and God did it.

Should probably grab the homework thread, but cbf. Wtf is this question asking me to do?

Use the molecules you have constructed (out of wine gums and tooth picks ftw) and test a single, double and triple bond to see if you can rotate the atoms on either side of the bond with respect to each other.

Which bond allows free rotation between the atoms joined?
Which bonds do not allow free rotation between the atoms joined?

What does it mean by rotation? Of course I can rotate them, they're lollies.

And yes, I know it's straightforward for you lot.

What is a bond in the first place? Generally, it is the sharing of electrons. So the more electrons you're sharing, the higher the electron density between the two atoms.

Pretty simple so far. The electron density in a sigma bond is symmetrical. What that means is in the model you have, the two atoms can rotate about each other like this:

YouTube - Ethane Rotation About the Carbon-Carbon Single Bond

This is ethane, the gray are the carbon, the yellow are the hydrogen atoms (the electrons in between aren't shown explicitly).

See how it's rotating constantly? There is only a single bond (e.g, one pair of electrons between them, so it allows for free movement). I don't know if you've learned about different conformers (gauche, anti) yet, but for now just know that some configurations are more stable than others, and thus the molecules spend more time in those configurations than others. But it's still constantly rotating.

However, once you have double or triple bonds (pi bonds in addition to sigma bonds), the electrons have really high density and are thus unable to rotate with respect to that bond like you saw in that video. They are more rigid (due to the extra electrons holding them in place) and can't rotate all that well.

If you ever do Pchem at university, you'll get into the math of quantum mechanics and things like that behind it, but for now, this should be a good enough understanding.

[Corli]

I'd say the answer they are looking for is that single bonds can rotate, while double and triple bonds can't. If you hold the one wine gum still, you should be able to rotate the other one freely with the single bond, while it shouldn't be possible to hold one still and rotate the other with the multiple bonds. I can't really explain it without having some toothpicks and winegums myself, post me some and you'll get a better answer.

[Flem274*]

What is a bond in the first place? Generally, it is the sharing of electrons. So the more electrons you're sharing, the higher the electron density between the two atoms.

Pretty simple so far. The electron density in a sigma bond is symmetrical. What that means is in the model you have, the two atoms can rotate about each other like this:

YouTube - Ethane Rotation About the Carbon-Carbon Single Bond

This is ethane, the gray are the carbon, the yellow are the hydrogen atoms (the electrons in between aren't shown explicitly).

See how it's rotating constantly? There is only a single bond (e.g, one pair of electrons between them, so it allows for free movement). I don't know if you've learned about different conformers (gauche, anti) yet, but for now just know that some configurations are more stable than others, and thus the molecules spend more time in those configurations than others. But it's still constantly rotating.

However, once you have double or triple bonds (pi bonds in addition to sigma bonds), the electrons have really high density and are thus unable to rotate with respect to that bond like you saw in that video. They are more rigid (due to the extra electrons holding them in place) and can't rotate all that well.

If you ever do Pchem at university, you'll get into the math of quantum mechanics and things like that behind it, but for now, this should be a good enough understanding.

I'd say the answer they are looking for is that single bonds can rotate, while double and triple bonds can't. If you hold the one wine gum still, you should be able to rotate the other one freely with the single bond, while it shouldn't be possible to hold one still and rotate the other with the multiple bonds. I can't really explain it without having some toothpicks and winegums myself, post me some and you'll get a better answer.

Ah, i've clicked now. Thanks guys.

[cover drive man]

E=MC2

What are the exact mathematical values for these say for instance I wanted to convert 1 milligram of helium into energy, what would be the exact numbers to use. Basically what proportion or numbers do I use (and please don't say you multiply it by the speed of light squared )

[silentstriker]

E=MC2

What are the exact mathematical values for these say for instance I wanted to convert 1 milligram of helium into energy, what would be the exact numbers to use. Basically what proportion or numbers do I use (and please don't say you multiply it by the speed of light squared )

1 milligram = 1*10^-6kg

so E = (1 x 10^-6kg) * (3 x10^8 m/s)^2 = 9*10^10 Joules.

[cover drive man]

I wasn't sure whether it was m/second or m/minute etc. Thanks.

[silentstriker]

Minute is not an SI unit. You won't see equations with that unit.

[cover drive man]

Sl? Speed of light?

[silentstriker]

International System of Units

[nightprowler10]

Sl? Speed of light?

Sports Illustrated.