ORGANIC - GCSE Chemistry (AQA Topic C7)

time for one of the beasti chemistry topics C7 it's organic organic compounds are those that have carbon forming the backbone of the molecules crude oil can be found underground and is the result of Plankton being buried underwater a long time ago it consists of mostly hydrocarbons that is molecules only made up of carbon and hydrogen atoms most of these are alkanes which are chains of single covalently bonded carbon atoms surrounded by hydrogen atoms as such there's always twice as many hydrogens as carbons in a molecule plus another two on the ends we can therefore write

a general formula for alkanes CN and then h2n + 2 all alkane names end with a whereas the beginning of the name tells you how long the carbon chain length is meth is one ethis 2 propis 3 butus 4 penes 5 hexis 6 and so on crude oil isn't useful as a mixture of all of these different length alanes so we use fractional distillation to separate them out we heat them so they evaporate and rise up the fractionating column apart from the very longest ones which stay as liquid generally used as bimon on roads the

column gets cooler the higher up the gases rise as different length alanes have different boiling points they condense back into liquids at different heights where they're then collected longer alkanes have higher boiling points because there are stronger intermolecular forces between them which more energy is needed to overcome the shortest alkanes remain as a gas even at the top we call this fraction LPG or liquid petroleum gas es because they're put into pressurized containers afterwards to transport and then turn into liquid LPG contains a range of chain length alkanes like all of the fractions Below in

LPG case it's up to four carbons long these are the other fractions you need to know petrol is the next longest fraction so it condenses just below LPG that's used in cars of course kerosene is used for jet fuel then diesel oil cars and lorries and things and heavy fuel oil is used in large ships as you can see these alkanes can be burned as fuel you should remember that complete combustion with oxygen produces carbon dioxide and water you know about their varying boiling points but you also need to know that longer fractions are more

viscous or have higher viscosity it's just a science you word for more thick and gloopy and shorter fractions are more flammable easy to burn but these different fractions can also be used to make solvents lubricants detergents and perhaps most importantly polymers used for Plastics polymers can be made from alkenes but not Al canes an alken is a hydrocarbon that has a carbon carbon double bond in by the way we can call this C double bond c a functional group because of this double bond we can also say that this molecule is unsaturated whereas alkanes are

saturated which essentially means that they're full that's why you can test for an alken which is a colorless liquid by adding bromine water which is orange if the mixture turns colorless that means that the bromine has bonded to the alen for example it bonds to to ethine by breaking that double bond into single bonds used to attach the bromines the proper name of this product by the way is one two di bromo ethane and this is saturated as you can hopefully see this can't happen with an alkan as it's already saturated of course so it

stays orange chlorine and iodine react in a similar way and water can also saturate an alen by attaching itself as an h and an O functional group we've now made an alcohol by the way more on this for triple in a bit now there are two more problems with Cru oil one is that the demand for shorter alkanes is much higher than that for longer ones also there aren't enough alkenes in it for our purposes cracking solves both of these problems that is breaking apart a longer alkane into a shorter alkane and an alen catalytic

cracking requires a temperature of around 550° c and a catalyst called a zeolite if there's no Catalyst you can just use an even higher temperature of over 800° which makes sense doesn't it this is called steam cracking let's take butane and crack it it can split right down the middle but there must be the same number of all atoms in the products that means that yes we make ethane but there's not enough hydrogen to make another ethane so instead it makes ethane as well the alken which of course is then useful for making polymers it

could also split here instead to make methane and propane cracking allows us to meet the demands for shorter alkanes for fuels as well as produce alkenes for making other materials more on polymerization for triple in a bit the rest of organic is just for triple so skip to chemical analysis if you're doing double like we mentioned earlier an alcohol is an organic compound with an O functional group their names always end with all so this is ethanol these can react with oxygen that is combust to make carbon dioxide and water if it's complete combustion and

carbon monoxide or carbon and water if it's incomplete combustion When there's less oxygen available reacting ethanol with sodium makes sodium ethoxide and hydrogen similarly for propanol and butanol just one of those random bits you need to know short alcohols like these can mix with water to produce a solution which gets more difficult as they get longer when an alcohol is oxidized without combustion that is with an oxidizing agent it makes a carboxilic acid that's a molecule with instead of Co it's co that's the functional group it still has the hydroxide the O group but it's

not an alcohol anymore the name of this would be ethanoic acid we can also get propanoic butanoic acid Etc polymers are super longchain alkanes made up of repeating sections made from monomers poly just means Lots mono just means one for example lots of ethenes the monomer can be joined together through addition polymerization to make polyethene or polye that's the polymer these monomers must have a double bond in note that even though it makes a long alkane we still use the name of the alken it's made from it's polyethene not poly ethane as you can see

this happens because the double bond split so carbon can bond to the next monomer and so on thankfully we only have to draw the repeating unit with brackets around it and the bonds coming out with an N on the outside showing that there are lots of these joined together condensation polymerization is when we join together two monomers that have two functional groups for example an alcohol and a carboxilic acid first let's look at the reaction between ethanol and ethanoic acid these can react to produce ethy ethanoate this is an Esther can you see water must

also be produced now let's react an alcohol with an O on both ends and a carboxilic acid with Co on both ends too now this reaction happens on both ends and we can make a chain of this Esther this would then be a polyester it doesn't matter what's in between the functional groups we can sometimes just write r as a Shand for the stuff in the middle or just a we box the process is the same every time again water is chucked out hence why it's called condensation polymerization you should remember amino acids from biology

they're the building blocks of proteins they have two functional groups an amino group nh2 and a carboxy group Co which we just saw hence why it's called an amino acid these can be polymerized to make polypeptides joining together different amino acids makes a protein DNA full name deoxy ribonucleic acid is the large molecule that stores genetic code it's made from two polymers that spiral around each other in a double helix and is made from four different monomers called nucleotides starch is also a natural polymer where the monomer is glucose and cellulose is a polymer that's

made from beta glucose and like we've just seen proteins have amino acids as they anonomous so I hope you found that helpful leave a like if you did and pop any questions or comments below I'll see you in the next video