organic chemistry

Question 1

give stages 1-2 of the crude oil timeline?

Answer 1

1.millions of years ago,there were many tiny animals and plants in the sea
2.when they died they fell to the bottom of the sea

Question 2

give stages 3-4 of the crude oil timeline?

Answer 2

3.at the bottom of the sea they were covered in mud
4.overtime layers of rock built up on top of the dead organisms

Question 3

give stages 5-6 of the crude oil timeline?

Answer 3

5.the rock put dead organisms in hot, high pressure,low oxygen conditions
6.these conditions over millions of years formed crude oil

Question 4

what is crude oil?

Answer 4

crude oil is a hydrocarbon that is a mixture of alkanes

Question 5

what are hydrocarbons?

Answer 5

hydrocarbons are compounds that contain only hydrogen and carbon

Question 6

what is fractional distillation?

Answer 6

is a method used to separate mixtures of liquids with similar boiling points

Question 7

describe the process for fractional distillation?(4 steps)

Answer 7

1.crude oil is heated,vapourised and enters at the bottom of the column
2.the vapour rises up the column which is hottest at the bottom and coolest at the top
3.the different liquids in the vapour will condense at their boiling points
4.fractions are then collected,these are mixtures over a small range of boiling point temperatures

Question 8

why is carbon a useful element for making large compounds?

Answer 8

each atom of carbon can form 4 strong bonds (covalent)

Question 9

what are alkanes?

Answer 9

alkanes are saturated compounds-every carbon atom has full single covalent bonds-no double bonds-hydrocarbons

Question 10

how can we describe the alkane series?

Answer 10

as a homologous series-they have similar properties and react in a similar way

Question 11

what is the general formula for alkanes?

Answer 11

CnH2n+2

Question 12

name four alkanes?

Answer 12

methane
ethane
propane
butane

Question 13

give the molecular formula for methane

Answer 13

CH4

Question 14

give the molecular formula for ethane

Answer 14

C2H6

Question 15

give the molecular formula for propane

Answer 15

C3H8

Question 16

give the molecular formula for butane

Answer 16

C4H10

Question 17

what is an alkene?

Answer 17

an alkene is an unsaturated type of hydrocarbon containing at least one double bond between carbon atoms

Question 18

state 2 differences between alkenes and alkanes?

Answer 18

1.alkenes are unsaturated hydrocarbons which contain at least one double bond between carbon atoms whereas alkanes are a saturated hydrocarbon which contains only single bonds between carbon atoms
2.the double bond in alkenes makes them more reactive than alkanes

Question 19

how do we test for alkenes?

Answer 19

to test for alkenes we use bromine water which is orange-if we shake our alkene with bromine water then the bromine water will turn colourless

Question 20

what is the key rule for balancing cracking equations?

Answer 20

the number of hydrogen and carbon atoms must be the same on both sides of the reaction

Question 21

explain the trend of boiling points in hydrocarbons?

Answer 21

as the length of the hydrocarbon chain increases the boiling point also increases
this is because longer chains have more intermolecular forces between them requiring more energy to overcome

Question 22

explain the trend of viscosity in hydrocarbons?

Answer 22

viscosity (how easily a substance flows) also increases as the length of the hydrocarbon chain increases due to more stronger intermolecular forces between carbon atoms making them less fluid and more viscous

Question 23

explain the trend of flammability in hydrocarbons?

Answer 23

flammability decreases as the chain length increases
this is because shorter chains are more volatile and ignite more easily whereas longer chains require more energy to vaporise and burn

Question 24

what is cracking?

Answer 24

cracking is a chemical process where useless long chain alkanes are cracked/broken down to produce more useful short chain alkanes and alkenes

Question 25

why do we use cracking?

Answer 25

because long chain hydrocarbons do not make good fuels-not very flammable which is a problem due to high demand for short chain hydrocarbons to used as fuels.

Question 26

what two ways can we crack hydrocarbons?

Answer 26

catalytic cracking steam cracking

Question 27

what conditions are required for catalytic cracking?

Answer 27

-high temperature and a catalyst(usually a transition metal)

Question 28

what conditions are required for steam cracking?

Answer 28

high temperature,high pressure and steam

Question 29

what can alkenes be used to make?

Answer 29

polymers

Question 30

what is complete combustion?

Answer 30

when a fuel is burnt in a good supply of oxygen-carbon dioxide and water are always the products

Question 31

what is incomplete combustion?

Answer 31

fuels burnt in a limited supply of oxygen carbon monoxide is always produced

Question 32

what is a polymer?

Answer 32

a large molecule made up of many small repeating units called monomers which are alkene molecules

Question 33

describe the structure and bonding of a polymer?

Answer 33

-each polymer molecule is made up of smaller units called monomers -very large molecules-the atoms in a polymer molecule are joined together by strong covalent bonds in long chains -only have single covalent bonds

Question 34

explain the properties of polymers? melting point

Answer 34

-high melting point-intermolecular forces between polymer molecules are strong compared to intermolecular forces between small molecules-require lots of energy to overcome

Question 35

explain the properties of polymers? solid at room temp

Answer 35

intermolecular forces of attraction between polymer molecules are relatively strong-in order to melt a polymer we have to break these intermolecular forces-takes a lot of energy-solid at room temp-high melting point