C6.2 (2) Flashcards
define a polymer
large molecules built up from small units (or monomers)
how does addition polymerisation work?
in terms of bonds
- C=C double bond in alkenes is removed to produce a C-C single bond
- the bonds then join with unsaturated molecules to form a long saturated polymer
how do you produce an addition polymerisation reaction?
react alkenes together at high pressure and a catalyst
what is special about addition polymerisation reactions compared to condensation polymerisation?
- addition polymerisation only produces one product
how would you generally represent the product of an addition polymerisation reaction?
as a repeating unit (so the alkane , with two lines sticking out of the bracket), and a small n
- REMEMBER ALKANE NLY HAS ONE LINE BETWEEN THEM AS BONDS HAVE OPENED UP *
what does the polymer name depend on?
eg. if propene is monomer, what is the polymer name?
depends on the name of the monomer
- propene becomes poly(propene)
- MONOMER NAME REMAINS SAME, BUT BOND DIAGRAM DOES NOT*
what is an addition polymerisation reaction simply?
when small monomers (alkenes) join together to form one large polymer (saturated hydrocarbon chain)
what is a condensation reaction?
two molecules reacting together to produce one large molecule and a water molecule
how many functional groups must there be within a monomer for it to react? (during a condensation reaction)
- at least 2
what do functional groups allow a monomer to do?
join to another monomer (as it has one on each side so can form a long chain)
how many monomers does each polymer (produced by a condensation reaction) usually contain?
100s or 1000s of monomers
what functional groups react together to produce a polyester?
(and how many of each one)
2 -OH groups (from alcohols) - HYDROXYL group
2 -COOH groups (from carboxylic acids) - CARBOXYL group
what is produced when a polyester is formed?
- an ester group ‘‘-COO-“
- water
what functional groups react together to produce a polyamide? - and how many of each one ,k
(and what makes up an amide group)
2 carboxyl groups (-COOH)
2 animo groups (-NH2)
-CONH
why are polyesters given their name?
and name the bond
- contain many ester groups (-COO-)
why are polyamides given their name?
- contain many amide groups (-CONH-)
what is a real life example of a polyamide?
a protein
explain how water is produced when a polyester is made
- OH lost off COOH group
- H lost of OH group
- CO and O join together to make a polyester
- OH and H lost join to form water
how do you represent a polymer after a condensation reaction?
using block diagrams (each block would represent a hydrocarbon group)
what 3 factors are needed to carry out a Addition reaction?
- high pressure
- high temperature
- with a catalyst
(addition,. condensation can occur without a catalyst at room temp and pressure)
how would you produce a polyester in a school lab?
- heat together an alcohol + carboxylic acid
in presence of an acid catalyst
uses of polyesters?
clothing/fizzy drink bottles
ie. a polyester named PET
uses of polyamides?
clothing/ carpets
ie. polyamide named nylon
what is DNA?
a polymer made from monomers (called nucleotides)
what does a nucleotide (in DNA) consist of?
- a phosphate group
- deoxyribose sugar
- an organic base
what bond forms between opposite bases within DNA?
hydrogen bonds
how many naturally occuring proteins (she means amino acids) are there?
20
how do animo acids join from end to end?
as they have a reactive functional group on each end
what does sucrose consist of?
simple sugars joined together (glucose + fructose)
what determines the reactions of organic compounds?
the generality of reactions of functional groups
BASICALLY FUNCTIONAL GROUPS CONTROL HOW ORGANIC COMPOUNDS REACT
define crude oil
a complex mixture of hydrocarbons (mainly alkanes)
why is crude oil able to be separated using fractional distillation?
as the different alkanes that make up the mixture have different boiling points
how is crude oil made?
- from the remains of dead marine creatures that lived millions of years ago
- these became buried deep in the sea bed after they died / rocks
- (pressure and temperature ?) chemical reactions eventually turned them into crude oil
explain (in terms of intermolecular forces), why fractional distillation is used to separate crude oil
- alkanes have different boiling points SINCE
- they have different numbers of carbon molecules (and therefore have different sized carbon chains)
- longer chained alkanes have a higher boiling point
- as the intermolecular forces between them are stronger
why do alkanes within crude oil have different boiling points?
- have different number of carbon molecules
- which affects chain length
- a longer chain length means intermolecular forces between them are stronger
- and so has a high boiling point
name the fractions when separating crude oil (highest to lowest)
LPG Petrol Paraffin Diesel Heating Oil Fuel Oil Bitumen
what is the mnemonic to remember the name of the fractions?
..
describe the separation of crude oil by fractional distillation
- oil is heated in the fractionating column
- it evaporates
- hydrocarbons condense on designated fraction + are extracted
- each fraction contains substances with similar boiling points
which gases have the lowest boiling points?
- refinery gases
ie. methane, ethane, propane, butane
(leaves through LPG at the top)
spec - describe the fractions
fractions = largely a mixture of compounds of formula CnH2n+2 which are members of the alkane homologous series
2 uses of crude oil
crude oil is the ……… source of …………… and is a …………… for the ……………….. industry
main, hydrocarbons, feedstock, petrochemical
how is modern life crucially dependant upon hydrocarbons?
each fraction obtained is used for something
ie. for plastics/oil/petrol
what is bitumen used for?
making roads
what is the paraffin fraction used for?
jet fuel
what kind of resource is crude oil?
finite resource
what is cracking?
a chemical reaction where large alkane molecules are converted to smaller alkene and alkane molevules
what are the conditions required for cracking to occur?
high temperature 600-700, catalyst - alumina or silica, closed system
describe what happens in cracking?
- hydrocarbons (separated by fractional distillation) are
heated to a high temperature - then passed over a catalyst of alumina or silica
what chemical reaction happens exactly during cracking?
in terms of bonds
the covalent bonds between the atoms (in large alkane molecules) break
why is cracking carried out?
- fractional distillation produces more long chained alkanes than short chained
- which are less useful
- cracking helps to produce more short chained (which are more useful)
MD:
- fractions with relatively large alkane molecules have high b.ps
- these do not flow easily and are difficult to ignite, so they are not useful as fuels
- fractions with relatively small alkane molecules have low boiling points - flow more easily, easier to ignite = more useful as fuels
what are small alkanes generally used for?
fuels
what are alkenes generally used for?
making plastic polymers
why are short chain alkenes more combustible?
as they have a low boiling point
how does a chemical cell work?
produces a potential difference until the reactants are used up
give the advantages of hydrogen-oxygen fuel cells
- no combustion (so no waste products)
- greater efficiency
- only emits water
- compact + lightweight
- no moving parts = more durable
disadvantages of hydrogen-oxygen fuel cells
- need fossil fuels to produce hydrogen (not found by itself on earth)
- storage of hydrogen fuel is difficult
- hydrogen fuel is highly explosive
- poisonous catalyst used
what is the word equation to model the chemical reaction occurring in a hydrogen-oxygen cell
hydrogen + oxygen -> water
how do hydrogen-oxygen fuel cells work?
- hydrogen enters cell
- it becomes oxidised at the anode (+)
- electrons lost then travel around the external circuit to the cathode (generating
electricity) - to the cathode (as there is a potential difference)
- hydrogen ions travel through the electrolyte = travel through PROTON EXCHANGE MEMBRANE
- they then react with the oxygen coming from other inlet
- and produce water
what charges do each electrodes have in an hydrogen-oxygen fuel cell?
anode (+) LEFT
cathode (-) RIGHT
what is the point of an addition reaction?
create a polymer (polyester or polyamide)
Thermosetting polymers
- strong covalent bonds between layers - can’t be reshaped easily
Thermosoftening polymers
Can be reshaped when heated Easily separated Can move over each other
What are thermosetting vs softening polymers
Plastics can be put into one of two categories, depending on how they respond when heated.
Thermosoftening plastics melt when they are heated. Most plastics that we come across in everyday life are thermosoftening plastics. This means that they can be recycled, which involves melting them before making a new product.
Thermosoftening plastics do not have covalent bonds between neighbouring polymer molecules, so the molecules can move over each other when heated and the plastic melts.
Thermosoftening plastics with no cross links between the polymer molecules
Thermosoftening plastics have no cross links between the polymer molecules
Thermosetting plastics do not melt when heated. They tend to char and burn when heated, but they are resistant to much higher temperatures than thermosoftening plastics. They are used to make electrical plugs, which must not melt, even if there is a malfunction and the wiring inside gets hot.
The polymer structure of a thermosetting plastic.
The covalent bonds in this thermosetting plastic are strong and prevent the plastic melting when it is heated
Define condensation polymerisation
involves monomers with two functional groups. When these monomers react they join together and produce water molecule(s)
What must the two monomers have in common for the condensation polymerisation reaction to occur?
The same functional groups
How do amino acids react
Amino acids react by condensation polymerisation to produce polypeptides. Different amino acids can be combined in the same chain to produce the polypeptide
Read c629 and look at the pictures
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How a chemical cell works - 3 - detailed
- exothermic reactions in the cell develop a potential difference or voltage between its two ends
- when the cell is connected to an electrical circuit, a current flows through the cell and the components of the cell
- this continues until one of the reactants is used up - the cell ‘goes flat’ and can no longer provide a potential difference
Examples pf chemical cells
Batteries in portable devices such as mobile phones and torches
What does a (hydrogen-oxygen) fuel cell do in a senetce
- produces electricity through a chemical reaction between a fuel and oxygen, without combustion happening
Overall symbol equation of reaction in hydrogen-oxygen fuel cell (state symbols) + words
- what type of reaction
Hydrogen reactions with oxygen in an endothermic reaction to produce water vapour:
2H2(g) + O2(g) —> 2H2O(g)
1st step of hydrogen oxygen fuel cell w/ words and equations
state symbols
1 - hydrogen molecules lose electrons and become hydrogen ions:
2H2(g) —> 4H+(aq) + 4e-
Hydrogen ions pass through a ‘proton exchange membrane’ to the other side of the fuel cell, and electrons travel through the external circuit to the other side of the fuel cell
2nd step of hydrogen oxygen fuel cell w/ words and equations
Statesybols
2 - hydrogen ions combine with oxygen and electrons at the other side to form water vapour:
4H+(aq) + O2(g) + 4e- —> 2H2O(g)
Why fractional distillation alone not good enough (2), and why cracking helps (2)
Fractional distillation alone produces:
- more of the fractions with large molecules and high boiling points that can be sold
- not enough of the fractions with small molecules and low b.ps that are in high demand
- Cracking helps an oil refinery match its supply of useful products, such as petrol, with its customers’ demand for them.
- cracking also produces alkenes - these are useful for making polymers
Carboxylic acid + alcohol
- what kind of reaction
- forms what
- condensation reactions
- organic compound called esters
- water
Ethanoic acid + ethanol
- word + symbol equatiobs
Ethanoic acid + ethanol —> ethyl ethanoate + water
CH3COOH + C2H5OH —> CH3COOC2H5 + H2O
propanoic acid + ethanol
The ester:
Ethyl propanoate
Naming esters:
- change the name of the parent alcohol to end in –yl
- change the name of the parent acid to end in –oate
- alcohol name goes to the front, acid name to the back
Propanol + ethanoic acid
Propyl ethanoate + water
How do fuel calls work - one card pb + include equations
