Chemistry questions

[Chaotic42]

Hey folks. I'm bored and I have some questions.

1. What is it exactly about a chemical that determines its properties? What makes table salt so different its components? What do the flourine atoms do that makes teflon so different from Ethylene which has hydrogen atoms in their place?

2. Is a plastic milk jug just one large molecule of polypropylene?

 

[sniperruff]

1) many factors... the physical structure, the chemical structure (what makes the chemical), temperature, light...

2) ummmmmmmmm no. think of it as a giant sheet of polypropylene bent in the shape of a jug

 

[Chaotic42]

Originally posted by: sniperruff
1) many factors... the physical structure, the chemical structure (what makes the chemical), temperature, light...

2) ummmmmmmmm no. think of it as a giant sheet of polypropylene bent in the shape of a jug

Forgive the ignorance, but isn't a solid block of pure metal just a big molecule? If so, why is the plastic different?

 

[DrPizza]

the type of bonding controls some of the properties.. The strength of the bonds, etc.

 

[ScrapSilicon]

Forgive the ignorance, but isn't a solid block of pure metal just a big molecule? If so, why is the plastic different?

you just answered it

 

[Siva]

MOLECULE. A collection of two or more atoms held together by chemical bonds; the smallest unit of a compound that displays the properties of the compound.

The smallest unit of a compound that displays the properties of the compound is the key. For example, a molecule of table salt would be a sodium atom bonded to a chlorine atom. So a milk jug is made up of many molecules of some plastic (polypropylene then?).

 

[Siva]

And a block of metal isn't just one molecule, a single atom of a metal is a molecule of that metal though.

 

[Shockwave]

Hey can you guys help me cook up some acid?

 

[Chaotic42]

Originally posted by: Siva
And a block of metal isn't just one molecule, a single atom of a metal is a molecule of that metal though.

So what is it that keeps the plastic together? What force keeps it from just falling apart?

See, I thought these things were big chains of CH with other stuff attached.

 

[Eli]

Originally posted by: Chaotic42

Originally posted by: sniperruff
1) many factors... the physical structure, the chemical structure (what makes the chemical), temperature, light...

2) ummmmmmmmm no. think of it as a giant sheet of polypropylene bent in the shape of a jug

Forgive the ignorance, but isn't a solid block of pure metal just a big molecule? If so, why is the plastic different?

No.. a block of metal is probably millions of {metal} molecules.

I know what you mean, though. It's very confusing.

For example, Chlorophyll is very similar to hemoglobin - the main difference being a magnesium atom in the center, instead of iron.

It's quite interesting how a slightly different grouping of the same atoms can make something totally different. I'm not exactly sure what that is called

 

[Siva]

Intermolecular forces. Um, I really wish I remember them better. London forces exist between every molecule, dipole-dipole forces exist between only polar molecules (molecules where one side has a stronger change than the other, for example in H-O-H [water] the oxygen atom is attracted to the hydrogen atom of other molecules, while in Cl-Cl, the charge is not "off balance"), and hydrogen bonding occurs when a hydrogen atom and an N, F, or O atom are in the same molecule, there is a strong attraction between the hydrogen and those three atoms. Hydrogen bonds are the strongest, then dipole, the london.

 

[Eli]

Originally posted by: Chaotic42

Originally posted by: Siva
And a block of metal isn't just one molecule, a single atom of a metal is a molecule of that metal though.

So what is it that keeps the plastic together? What force keeps it from just falling apart?

See, I thought these things were big chains of CH with other stuff attached.

Damn, I wish I knew how to answer the questions better. It's like I know the answer, but I don't.. lol

Obviously, the molecules of plastic are locked together.... I don't really know what force keeps it from just falling apart.

You could say the same thing about any substance really. Why doesen't water just fall apart?

The molecule is stable.. I dunno..lol

 

[Chaotic42]

Originally posted by: Siva
Intermolecular forces. Um, I really wish I remember them better. London forces exist between every molecule, dipole-dipole forces exist between only polar molecules (molecules where one side has a stronger change than the other, for example in H-O-H [water] the oxygen atom is attracted to the hydrogen atom of other molecules, while in Cl-Cl, the charge is not "off balance"), and hydrogen bonding occurs when a hydrogen atom and an N, F, or O atom are in the same molecule, there is a strong attraction between the hydrogen and those three atoms. Hydrogen bonds are the strongest, then dipole, the london.

That's what keeps a plastic together. Metals, however, have covalent bonds which are much much stronger.

So when you slam a piece of plastic together and it breaks, you've applied enough force to overcome the specific intermolecular forces for that type? Those forces determine the strength of the material?

 

[Siva]

yes, pretty much. The stronger the intermolecular forces, the higher the melting point, the higher the boiling point, etc...

 

[Eli]

Originally posted by: Siva
yes, pretty much. The stronger the intermolecular forces, the higher the melting point, the higher the boiling point, etc...

Huh...

But when you rip a piece of plastic apart, you aren't breaking the molecules... are you? You're just breaking the bond "between" the molecules, or something.. if that makes sense?

If you were ripping molecules apart when you ripped a piece of plastic, wouldn't you end up with some raw elements and energy?

I mean.. If you had a fishtank full of water, and you slam your hand into the water, splashing some of it out.. you haven't turned the water into hydrogen and oxygen, but you've "broken" the bond between the water molecules...

 

[Siva]

No, you aren't ripping apart the molecules themselves... you're ripping one molecule apart from another. So if you have a diamond that is made of 1000 Carbon atoms (just a completely hypothetical example, I forget how many C atoms make up the crystal lattice of diamonds) and you cut the diamond in half, you would have two pieces each containing 500 carbon atoms each.

I feel like I'm forgetting a lot, its been far too long since I've been in chemistry class..... summer is EATING MY BRAIN.

 

[Eli]

Originally posted by: Siva
No, you aren't ripping apart the molecules themselves... you're ripping one molecule apart from another. So if you have a diamond that is made of 1000 Carbon atoms (just a completely hypothetical example, I forget how many C atoms make up the crystal lattice of diamonds) and you cut the diamond in half, you would have two pieces each containing 500 carbon atoms each.

I feel like I'm forgetting a lot, its been far too long since I've been in chemistry class..... summer is EATING MY BRAIN.

Yeah.

I think we're getting confused as to whether he's asking what keeps raw atoms together in the form of a molecule of {whatever}, or if he's asking what keeps already formed molecules together.

I vaguely remember learning about it at some point. I can't think of the term, though.. what is it called when, for example, water is attracted to other molecules of water?

 

[Chaotic42]

I'm asking what keeps already formed molecules together.

Most of my physics knowledge is about really small things and really big things.

 

[Siva]

That's what i was saying the intermolecular forces are.... they keep molecules together. What attracts the atoms within the molecules is completely different, that's either covalent or ionic bonding which has to do with electron sharing.

Intermolecular means between molecules, Intramolecular would be inside the molecule.

 

[Chaotic42]

Originally posted by: Siva
That's what i was saying the intermolecular forces are.... they keep molecules together. What attracts the atoms within the molecules is completely different, that's either covalent or ionic bonding which has to do with electron sharing.

Intermolecular means between molecules, Intramolecular would be inside the molecule.

I was just answering Eli's question about what question I'm asking... That's an odd sentence.

 

[Eli]

Originally posted by: Siva
That's what i was saying the intermolecular forces are.... they keep molecules together. What attracts the atoms within the molecules is completely different, that's either covalent or ionic bonding which has to do with electron sharing.

Intermolecular means between molecules, Intramolecular would be inside the molecule.

Ahh, Ok. I see, yeah.

So that makes sense then. It was me that was getting confused between intra and intermolecular, at least regarding the question.

 

[Siva]

Originally posted by: Chaotic42

Originally posted by: Siva
That's what i was saying the intermolecular forces are.... they keep molecules together. What attracts the atoms within the molecules is completely different, that's either covalent or ionic bonding which has to do with electron sharing.

Intermolecular means between molecules, Intramolecular would be inside the molecule.

I was just answering Eli's question about what question I'm asking... That's an odd sentence.

I was just answering Eli's question about what question I'm answering, I guess?

Oh my god I hate thinking. I need to get back to school.

 

[gururu]

polar(charge/charge interactions) and nonpolar(van der waals or london) interactions occur between molecules keeping them together. some substances like water are heavy on the polar interactions , while some like oil are heavy on the nonpolar interactions. waxes are similar to oils except that they have a higher melting point; this is because they have stronger intermolecular forces (takes more energy to disrupt their noncovalent interactions). salts do not form covalent bonds. they form through the creation of ionic bonds between atoms. ionic bonds are nearly impossible to break, as observed by their incredibly high melting points.
teflon works by virtue of its incredibly tight intermolecular forces due to the incorporation of fluorine. each carbon is tightly wrapped in flourines which draw in closely due to small bond lengths. The carbon remains hidden and quite unavailable for interaction(sticking) with or disruption by(solvation) other molecules. The polymer itself is very nonpolar as the C-F dipoles cancel themselves out. so polar substances like water slide right off.
all plastics go through a melting process which inevitably leads to a heterogeneous mixture of 'plastic molecules' of variable length. when cooling, the molecules line up according to non-covalent forces forming a solid.
metal is far different than polymers. metals do not form strictly covalent or ionic bonds. a chunk of metal is simply a cluster of atoms organized in such a way that maximal sharing of electrons is allowed. Each atom is actually fairly uncommitted to its nearest neighbor, such as would be a molecule or polymer in a wax or a plastic. Even molecules in crystals are far more committed to nearest neighbors than metal atoms in a metal, because metals are not so dependent on order.

 

[Chaotic42]

And a salt is just an acid that has had its hydrogen replaced by metals?

 

[gururu]

Originally posted by: Chaotic42
And a salt is just an acid that has had its hydrogen replaced by metals?

well, almost anything with an undisrupted ionic bond is a salt.