Topic 5 - Crude Oil

Question 1

what is a hydrocarbon?

Answer 1

• molecule that contains ONLY hydrogen and carbon atoms

Question 2

what is a homologous series?

Answer 2

a series of compounds which
- have the same general formula,
- share similar chemical properties,
- neighbouring compounds differ by CH2 units

Question 3

what are 3 properties of homologous series that change as you go up or down?

Answer 3

• boiling point
  -viscosity
• ease of ignition

Question 4

boiling point

Answer 4

the LARGER the hydrocarbon, the HIGHER the boiling point
they have more intermolecular forces which require more energy to break

Question 5

viscosity

Answer 5

the LARGER the hydrocarbon, the HIGHER it’s viscosity

Question 6

ease of ignition

Answer 6

the LARGER the hydrocarbon, the HARDER it is to ignite

Question 7

alkanes

Answer 7

• saturated hydrocarbons
• each carbon atom bonds to 4 atoms, only covalent bonds
• formula : CnH2n + 2

Question 8

alkenes

Answer 8

• unsaturated hydrocarbons
• they have a double C=C bond, not all carbon atoms form 4 bonds
• formula : CnH2n

Question 9

what is crude oil?

Answer 9

• complex mixture of many different hydrocarbons with differing lengths

Question 10

how is crude oil formed?

Answer 10

• at high temp and pressure
• from fossilised remains of plants and animals millions of years ago

Question 11

what is crude oil used for?

Answer 11

• finite resource
• main source of useful substances and feedstock of petrochemical industry

Question 12

what are fractions of crude oil?

Answer 12

simpler, more useful mixtures than crude oil that contain groups of hydrocarbons of similar lengths

Question 13

what process is used to separate crude oil into fractions?

Answer 13

fractional distillation

Question 14

fractional distillation

Answer 14

• crude oil is pumped into a fractionating column
• this has a temp gradient which is hottest at bottom and coldest at top
• crude oil is heated so most of it evaporates
• gas rises up the column and gradually condenses at different temperatures
• explain why similar length condense at same time

Question 15

order of crude oil fractions from highest to lowest
( R , P , K , D , F , B )

Answer 15

• refinery gas
• petrol
• kerosene
• diesel
• fuel oil
• bitumen

Question 16

refinery gas

Answer 16

used for domestic heating appliances and cooking

Question 17

petrol

Answer 17

fuel in cars

Question 18

kerosene

Answer 18

fuel in aircraft

Question 19

diesel oil

Answer 19

fuel in larger vehicles

Question 20

fuel oil

Answer 20

fuel in power stations

Question 21

bitumen

Answer 21

used to surface roads
used for roofs of buildings

Question 22

combustion of hydrocarbon

Answer 22

hydrocarbon + oxygen -> CO2 + H20

Question 23

when does incomplete combustion of hydrocarbon happen

Answer 23

when hydrocarbons are combusted in insufficient oxygen supply

Question 24

what harmful products can incomplete combustion cause?

Answer 24

• soot ( carbon )
• carbon monoxide
• sulfur dioxide
• nitrogen oxides

Question 25

carbon monoxide dangers

Answer 25

- colourless, odourless and toxic gas - binds to haemoglobin in blood in RBCs that normally carries O2 - less oxygen is transported around the body - lead to fainting or even death

Question 26

soot dangers

Answer 26

- tiny particles of carbon that deposit as black dust ( soot ) - makes buildings look dirty - reduces air quality and contributes to global dimming : blocks sunlight - causes respiratory problems

Question 27

sulfur dioxide

Answer 27

- when fossil fuels are burned, sulphur dioxide can be formed due to sulphur impurities - mixes with water in clouds to form sulphuric acid ' clouds ' which precipitate as acid rain - this corrodes metal structures and kills plants and harms ecosystem,

Question 28

nitrogen oxide

Answer 28

- when fuels are burned it releases a lot of energy in the form of heat - at the high temp reached in combustion engine, N2 can react with O2 to form nitrogen oxides - can cause petrochemical smog and cause acid rain - which causes headaches and tiredness

Question 29

advantages of hydrogen as a fuel

Answer 29

- only waste product is water which causes no pollution - it is produced from a renewable resource

Question 30

disadvantages of hydrogen as a fuel

Answer 30

- special, expensive engine required to use hydrogen as a fuel - hydrogen very flammable so hard to store safely

Question 31

what is cracking?

Answer 31

breaking down larger, saturated hydrocarbons into smaller hydrocarbons (some are unsaturated alkenes )

Question 32

why do we use cracking?

Answer 32

- short chain hydrocarbons are more useful because they are more flammable, so ignite more easily - this makes them more useful as fuels

Question 33

two conditions needed for cracking?

Answer 33

- catalysts - high temperatures ( 400 - 700 )

Question 34

which gases formed the early atmosphere?

Answer 34

- gases released from intense volcanic activity

Question 35

what gases were in the early atmosphere?

Answer 35

- mostly carbon dioxide - small amounts of other gases ( nitrogen, water vapour and methane ) - little or no oxygen

Question 36

composition of today's atmosphere

Answer 36

Nitrogen: About 78% Oxygen: About 21% Carbon dioxide: About 0.042%

Question 37

how did the amount of carbon dioxide decrease:

Answer 37

- absorption of oceans - absorption by plants and algae

Question 38

formation of oceans

Answer 38

- as the Earth cooled down - water vapour condensed forming the oceans

Question 39

absorption of CO2 by oceans

Answer 39

- when the oceans formed, CO2 from atmosphere dissolved into them - dissolved CO2 formed carbonate precipitates

Question 40

absorption of CO2 by oceans ( p2 )

Answer 40

- when marine animals evolved , their skeletons contained carbonates from oceans - when they died, they formed sedimentary rocks such as limestone - locked CO2 away

Question 41

absorption by plants and algae

Answer 41

algae and green plants absorbed CO2 in the atmosphere and used it in photosynthesis to make glucose

Question 42

increasing amount of oxygen

Answer 42

- algae and green plants produced oxygen by photosynthesis - oxygen created the ozone layer (O3) that blocked harmful rays from Sun - allowing more complex organisms to evolve

Question 43

test for oxygen

Answer 43

- put a glowing splint near a test tube containing gas - if it is oxygen, the splint will relight