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AQA Chemistry GCSE > Organic Chemistry > Flashcards

Organic Chemistry Flashcards

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1
Q

what is crude oil

A

a finite resource found in rocks.
- mixture of hydrocarbons

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2
Q

what are hydrocarbons

A

molecules that contain hydrogen and carbon atoms only.

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3
Q

what is crude oil made of

A

Formed over millions of years from the remains of tiny sea creatures called plankton, which were buried in the mud

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4
Q

formula for alkanes

A

CnH2n+2

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5
Q

what are the first four alkanes

A
  • methane
  • ethane
  • propane
  • butane
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6
Q

what are some of crude oil uses

A
  • fuels such as petrol, diesel, kerosene, heavy fuel oi
    solvents
    lubricants
    detergents
    liquified petroleum gas
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7
Q

what is a homologous series

A

a family of organic compounds which have the same functional group and similar chemical properties

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8
Q

properties of alkanes

A
  • have the same general formula
  • show a gradual variation in physical properties, such as their boiling points
  • have similar chemical properties
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9
Q

what are saturated hydrocarbons

A

hydrocarbons which have single carbon to carbon bonds, like alkanes

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10
Q

what technique is used to separate crude oil

A

fractional distillation

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11
Q

why is fractional distillation used

A

because different hydrocarbons have different boiling points

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12
Q

how does the distillation of crude oil work

A
  1. heated crude oil enters a tall fractionating column, which is hot at the bottom and gets cooler towards the top
  2. vapours from the oil rise through the column
  3. vapours condense when they become cool enough
  4. liquids are led out of the column at different heights
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13
Q

properties of smaller hydrocarbons

A
  • weak intermolecular forces
  • low boiling points
  • they don’t condense, but leave the column as gases
  • flammable
  • low viscosity
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14
Q

what is fractional distillation used for

A

to separate different hydrocarbons

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15
Q

properties of larger hydrocarbons

A
  • stronger intermolecular forces
  • high boiling point
  • they leave the column as hot liquid bitumen
  • less flammable
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16
Q

what are useful mixtures called

A

fractions

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17
Q

what does each fraction of crude oil contain

A

hydrocarbons with a similar number of carbon atoms

18
Q

hydrocarbons can undergo incomplete or complete combustion, what does this depend on?

A

the amount of oxygen available

19
Q

properties of complete combustion

A
  • carbon dioxide and water are produced
  • the maximum amount of energy is given out
20
Q

combustion equation

A

hydrocarbon + oxygen → carbon dioxide + water

21
Q

properties of incomplete combustion

A
  • poor supply of oxygen
  • water still produced
  • carbon monoxide and carbon dioxide produced
  • less energy given out
22
Q

what is cracking

A

a reaction in which larger saturated hydrocarbon molecules are broken down into smaller, more useful hydrocarbon molecules,

23
Q

properties of cracking

A
  • the original starting hydrocarbons are alkanes
  • the products of cracking include alkanes and alkenes, members of a different homologous series
24
Q

equation for alkenes

A

CnH2n

25
Q

properties of catalytic cracking

A
  • temperature at approximately 550 degrees
  • catalyst of zeolite
26
Q

properties of steam cracking

A
  • high temperatures over 800 degrees
  • no catalyst
  • steam
27
Q

why is cracking important

A
  • it helps match the supply of fractions with the demand of them
  • It produces alkenes, which are useful as feedstock for the petrochemical industry
28
Q

why do we use cracking

A
  • There is a high demand for fuels with small molecules and so some
    of the products of cracking are useful as fuels.
  • Alkenes are used to produce polymers and as starting materials for
    the production of many other chemicals.
  • very often, fractional distillation of crude oil produces more of the larger hydrocarbons than can be sold, and less of the smaller hydrocarbons than customers want.
    -Smaller hydrocarbons are more useful as fuels than larger hydrocarbons. Since cracking converts larger hydrocarbons into smaller hydrocarbons, the supply of fuels is improved. This helps to match supply with demand.
29
Q

properties of alkenes

A
  • saturated (double cc bonds)
  • more reactive than alkanes
  • can form polymers
  • will react with bromine water and turn it from orange/brown to colourless
30
Q

Examples of things made from crude oil

A

Plastic, petrol, pharmaceuticals, cosmetic

31
Q

Where do you find crude oil?

A

Rock

32
Q

what is viscosity

A

tells us the thickness of a fluid - fluids with a high viscosity flow slowly

33
Q

What does flammability tell us

A

How easily a hydrocarbon combusts

34
Q

what do the properties of hydrocarbons depend on

A

the size of the molecule

35
Q

examples of things that run on hydrocarbon fuels

A

should
planes
cars

36
Q

what happens during combustion

A
  • energy is released
  • hydrogen and carbon atoms are oxidised
37
Q

stages of fractional distillation

A
  • often takes place in large columns which are found in oil refineries
    1. crude oil is heated to a very high temperature, causing the crude oil to boil (all of the hydrocarbons evaporate and turn into a gas)
  1. the crude oil vapour is now fed to the fractional distillation column
  2. the column is hotter at the bottom and cooler at the top
  3. hydrocarbons condense when they reach their boiling point, and the liquid fractions are then removed
  4. the remaining hydrocarbons continue to move up the column, and these condense when they reach their boiling point
38
Q

where are long chain hydrocarbons removed

A

from the bottom of the column as they have v high boiling points

39
Q

where are shorter chain hydrocarbons removed

A

the top of the column as gases, they do not condense

40
Q

what is a feedstock

A

a chemical that’s used to make other chemicals

41
Q

examples of feedstocks made using fractions

A

solvents
lubricants
detergents
polymers

42
Q

why don’t long chain hydrocarbons make good fuels

A

cos theyre not very flammable

AQA Chemistry GCSE (27 decks)

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