How can molecules be so different when they are made of the same atoms. Say shorter hydrocarbon vs larger?

Question

Like gasoline is very different from other pure hydrocarbons. Methane different from ethane. In a solid form, molecules are packed together. Why when they are packed together are they not the same as smaller numbers of larger molecules? What makes a molecule so different when say only one more carbon is added to the chain!?

Also I mean, say a chiral compound is R one time, S the next. So the molecule is blue, or red. Or it smells bad, or good. Say you add a nitro group to something. It can still be very different than another molecule with that group in another location. Larger hydrocarbons are different some smaller, when all that is happening is the lengthening of the chain. We can change a single bond to a double, and drastically change the molecule. This is hard to explain my question, sigh.

Steel is the same in a solid form, a ring, a scaffold. Why are molecules different when arranged in different ways, but still the same building blocks? Not just different, but so different.

Answer 1

When atoms are bonded to each other they begin to function as a whole and not as the sum of their parts. Larger chains can have a huge electronegative atom on one side and make the whole molecule like a magnet, thus making a boiling point increase, or a heat of combustion difference. Or a molecule can be completely symmetrical in every way and be just sitting there. As with hydrocarbons, when you add more carbons, it is not necessarily a chain anymore, it could be a box, or a cross, a zigzag, and to further complicate things, under the right conditions, it can change its shape many thousand times per second. With different shapes come different properties. Gasolene is a combination of many hundred different types of hydrocarbons. Methane is one carbon with four hydrogens. Very light, and symmetrical thus it is a gas at room temperature. Where Octane is more commonly a liquid with eight carbons and 18 hydrogens. Molecules react magnetically with each other and it is this magnetism that causes the phenomena that you ask about. The atoms of one molecule even react with each other (sterics) and sometimes they are extremely unstable...enter dynamite. It is important to remember that when a large molecue breaks, it breaks into pieces that have their own properties (like boiling point, flash point, melting point) and the breaking of these molecules is sometimes unpredictable.
There is no easy answer, just think that everything has to do with shape, magnetism, and size. The difference between a babana smell and a grape smell is only a slight varience in exposed surface area of the molecule. Shape is how drugs work, how hormones work and how bacteria can kill. Hope that this helped.

Answer 2

This is an interesting comparison, but it really isn't a good one. For one thing - planets orbit stars because of gravity -- electrons orbit protons/neutrons because one is positively charged and one is negatively charged. For another -- electrons orbit the nucleus extremely fast, while it takes years for most planets to orbit their star. The nucleus of an atom is made of two different atomic particles which are not nuclear reactors -- a star is basically just a gigantic nuclear reactor burning itself up because of its own gravity. More than one electron orbits in each energy level around the nucleus, but if more than one planet orbited around in the same plane it would eventually crash into the other planet and this would create a single planet. Electron orbits are all over the place, while a planet stays on a basically linear orbital plane. --- The reason the comparison seems to make sense is the popular Bohr model of an atom. It is a great way to model an atom, but you have to realize that it is not a very accurate depiction of what an atom really would look like.

Answer 3

A sugar cube takes longer to dissolve than a spoonful of sugar because it is more packed together.

On a molecular level it may be different, I don't know the combustion rate of methane vs. propane off the top of my head, but the principle is the same: change the size and shape and it will react to conditions differently.

Answer 4

its amazing isn't it, but the differences are not that surprising if you look at the the trends and at functional groups

your example of simple hydro-carbon chains starting with methane is a good one for trends

methane is a very volatile gas, very difficult to liquify
add one carbon to the chain you get
ethane, a volatile gas that is less difficult to liquify, but still hard
add another carbon to the chain you get
propane, normally a gas but fairly easy to liquify
add another carbon we get
butane, normally a gas but the tiny pressure in a lighter liquifies it
add another and you get
pentane a liquid at normal temperatures, but boils so easily
haxane, a more stable liquid

and all these compounds are very flammable and produce the same products of combustion

it is certainly remarkable the diversity of our world built out of a relatively few atoms, but it isn't unpredictable

Answer 5

Thats a great question. I can not answer exactly but I think it has to do with how they bond tegether.

Answer 6

Do your own homework