Hey everyone it's time for some chemistry and specifically this is gonna be a little bit of organic chemistry that pertains to everyday life and what i was asked was about natural gas someone was asking me about natural gas.
And propane and what's the difference and that reminded me that something we haven't talked about are some really basic structures of organic compounds and so let's start out first and talk about you know what are these.
Natural gas these are both carbon based fuels and so what that means is that we are going to have carbon of course okay and also we have hydrogen.
And these are the only two elements so the chemical symbol for carbon c and if carbon is bonded these bonds here these are sharing electrons so each atom has its nucleus but also has electrons those electrons can be shared with other.
Atoms so this compound here that has just one carbon and the maximum number of hydrogens around it this is the simplest carbon-based fuel and this is called methane methane is the major component of natural gas.
Now it's not all of it because natural gas also has a couple other carbon-based compounds but most of natural gas is methane okay another compound that is in natural gas is if instead of just one carbon you have two so two carbons bonded together.
And now we because these carbon-based fuels also have hydrogen these carbons are surrounded too and bonded to hydrogen this compound here that has two carbons is called methane.
A little bit more okay some air ethane this is this is secondary component okay so most of natural gas is as i said methane with lupidapping that is most of it but there is also oh sorry secondary component in natural gas.
Okay but there is another component and that is this third component because these are these are mixtures these come out of naturally occurring natural gas fields various places around the world siberia the middle east north america okay.
So there's also a three carbon compound once again surrounded by hydrogens as well and notice the names of these compounds i'm talking about they all end in a methane ethane and now this one this one is.
Propane okay so there is a little bit of propane but it is a a minor and natural gas so this ending ain that we see that is actually telling us that the bonds between each of these carbons is a single bond.
That means that there are two electrons being shared so one bond has two electrons there are some compounds that have double bonds so instead there's four electrons being shared when there's a double bond then we see a different ending here we don't see aim.
We see e and e we're not gonna do the the naming conventions but i did just want to mention that okay so natural gas mostly methane there's a little bit of propane so when you get propane you buy propane that is where the propane has been.
Separated out and what you're buying is mostly what you're buying is mostly just this propane here okay so what we have here are these three carbon-based compounds and all three of them are gases at room temperature and so that's where we need to store.
Them as a gas and we need to then have some kind of way for them to come out of a valve and then we light them on fire they burn in that way okay and that's different from gasoline right gasoline at room temperature is a liquid and so when we're filling up our gas tanks.
Then that's actually a liquid that goes into our gas tank so let's move on from this question of the difference of natural gas and propane and let's ask this other question that's about gasoline okay so on our way to talking about that.
I am going to mention one other related fuel you're gonna start seeing a pattern here okay so with this one once again this will look familiar i've got carbons come on.
Carbon's bonded together one of my recent videos i used pencil instead of the calligraphy bed because my calligraphy pens have been having problems lately okay there we go so these three carbons we had this fourth one we had three for propane but now we have.
Four so the carbon-based fuel that has four carbons around it once again hydrogens okay so that's the same but now because we have four carbons this is called butane.
So if you're familiar with butane lighters we notice that there's now a difference between how butane exists at room temperature versus methane ethane and propane that we just talked about this is now a liquid right.
Liquid so there's something that has happened that's different from butane versus methanol and before we talk about that i'm going to talk a little bit about gasoline so you know the difference between all these fuels.
Okay and just like we saw with natural gas that's a mixture of methane ethane and propane we have a mixture these are still carbon based so these carbon-based fuels so it's not just one compound that's in there.
And one of those possible compounds you could guess if we think about the names that we've seen so far butane propane ethane when you think of gasoline and you think of one of the labels that's on a gasoline tank is that term octane and that is.
Because of exactly what it sounds like that there are eight of our carbons now what gets really interesting here is that they are not necessarily all bonded in a chain so here i have five carbons in a chain but another thing.
That happens is something called branching and so here's one two three four five in a row if we add this six seven and if we add another one let's say here okay we now have eight carbons okay so this is octane.
Now all of you who have taken organic chemistry you can absolutely do an exercise on your own where you would name this using the conventions that you've learned in organic chemistry okay but my point here is for beginning chemists.
Just to see the main point here is that we have these eight carbons now these carbons they are surrounded by these hydrogens but now we're getting you really know to put a lot of them here and i don't know if i have the patience for putting them on here or not let's see squeeze that in there.
Okay i'm gonna make them small so we can just focus on the carbons so this is just one i'll squeeze it this is just one of the carbon based fuels that's mixed in gasoline and there is there are different ways that this octane can be branched.
And also there are some heptane molecules that are in there heptane has seven carbons instead of eight so the octane rating is telling you what percentage of a specific type of branched octane the one that really burns the best in the pistons.
It gives the most the smoothest action of the pistons when the engine is working to combust those molecules in there and then that combustion which is essentially the fuel burning and that is releasing heat and when it burns it is releasing.
Carbon dioxide and water as it reacts with oxygen and so that outward motion of the gases that are formed causes expansion of the piston that does work it causes piston to move and some forms of octane cause a nice smooth action of the piston and that has been designated as a.
100 octane rating and so the different types of fuels depending on the octane rating is just telling you what percentage of that nice smooth burning octane is in there how that mixture compares to a mixture of octane and heptane heptane has an octane rating of zeros.
How that one's designated but there's a little bit of it mixed in that gives it a lower octane rating so we never we never see any octane rating of 100 anywhere because all gasolines have a little bit of peptane and some other types of octane that don't.
Burn quite as smoothly as that ideal one okay so let's finish off with this question of why is this i'll add this in octane is liquid okay just like our butane we noticed it's liquid okay put these up here let's see if we can fit put them mostly.
In here okay these three these are gas at room temperature these two or liquid at room temperature okay so why is that okay so what's happening here is that these three molecules are a lot smaller all right and so they are attracting.
Each other less and this is something that i actually have another video about intermolecular forces intermolecular forces are the attractions from one molecule to another and when molecules are smaller those attractions are less.
So these molecules are not attracting each other very much which means they stay further away from each other and they tend to be in the gas phase the gas phase molecules are very very far away from each other as compared to when they're in the liquid phase.
So liquid phase and solid phase those are called condensed phases because the molecules are very close together so something very special has happened between the size of a molecule that has three carbons and the size of one has four that's essentially the tipping point.
Butane is just large enough has enough electrons in it because of all these atoms it's large enough that it attracts itself a bunch of these butane molecules are attracting each other enough to keep them close together and to be a liquid and so it follows that.
Gasoline that has heptane and octane these much larger molecules right they're almost twice as big as the butane that these would also be liquid all right so you might ask yourself okay so what point could i have a carbon-based.
Compound that is heavy enough or that is large enough i mean where it attracts itself so much that it stays as a solid not as a liquid okay and that is at the point of about 20 right around 20 carbons this is where you start to get.
These softer low melting point kinds of compounds and so like an example this would be like a wax okay so this would be like a candle wax that is a low melting point but it is solid at room temperature all right but there are some carbon-based compounds.
That can withstand higher temperatures and an example of this would be once you get up to about 36 and i'm so sorry i realized i'm totally off or you can see so let me move this up okay someone took 20 carbons now we're in the we have enough enough carbons where it's.
Solid okay where this is liquid now we have solid now 36 carbons we are large enough to be in the realm of asphalt okay so these are definitely a higher melting point.
At least we should hope so right on those hot days on our roads but it is interesting that essentially asphalt is not that dissimilar from candle wax long long chains of carbons strung together you could almost think of them like.
Pieces of yarn and they're kind of interwoven and they cross and they go you know but ultimately they are just these long chains that are attracted to each other quite strongly and so you end up having a fairly strong substance so it can withstand.
The weight of all these cars and trucks driving over it for years but it does because it's these long strands like this it does have a little bit of give to it and that's important too for roads being able to last years they do need to have some give.
Unlike if it was made out of salt or something like cracks so if there's too much weight it would just make a big crack in it asphalt is this kind of slightly squishy almost it's still a strength to it but it can move ever so slightly especially changes of weather.
Season to season really cold in the winter hotter in the summer can expand and contract and we do see some cracks in asphalt but they're not huge cracks so that's why asphalt's used for roads has these very nice properties all right well there's a little bit of.
Organic chemistry as it applies to everyday life with the fuels that we burn whether it be natural gas mostly methane or propane that we use for propane tanks for a lot of things or butane that we use in lighters mostly and then of course gasoline that has a lot of octane in it.
And then our bigger carbons like waxes and fulton all right well thank you once again always feel free to tell me what your requests are i have a running list and i just keep pulling from the list so thank you so much for your comments and i will see you next time.
Thank you you
versuszone