C1.4 Crude oil and fuels

Question 1

What is a mixture?

Answer 1

A substance that consists of two or more elements or compounds not chemically combined together. The chemical properties of each substance in the mixture are unchanged.

it is possible to separate the substance in a mixture by physical methods including distillation.

Question 2

What is a hydrocarbon?

Answer 2

A molecule made of hydrogen and carbon atoms only.

Question 3

What are saturated hydrocarbons called?

Answer 3

alkanes

Question 4

What is the general formula of alkanes?

Answer 4

CnH2n+2

Question 5

What are the 1st 4 alkanes?

Answer 5

methane, ethane, propane, butane

Question 6

What is crude oil?

Answer 6

A mixture of a very large number of compounds

Question 7

Desccribe how a fractionating column work

Answer 7

it works continuously.

crude oil is pumped in at the bottom

Different compounds within the mixture have different boiling points so vaporise at different temperatures

vaporised oil rises up the column

Vapours condense at different fractions (at their boiling points)

Question 8

What the properties of short hydrocarbons

Answer 8

lower boiling point- more volatile

less viscous (thick)

more flammable

Question 9

What does it mean if a hydrocarbon is saturated?

Answer 9

all the atoms have formed bonds with as many other atoms as they can

Question 10

Describe how the uses of hydrocarbons depend on their properties

Answer 10

more volatility- lower boiling point - ideal as bottled gas

very viscous- covering roads

Question 11

in a fractionating column, each fraction contains molecules with…

Answer 11

a similar number of carbon atoms

Question 12

What elements are in most fuels.

Answer 12

carbon and/or hydrogen and may also contain some sulfur

Question 13

What gases are released into the atmosphere when fuels are burnt?

Answer 13

carbon dioxide, water, carbon monoxide, sulfur dioxide, oxides of nitrogen, particulates

Question 14

When are oxides of nitrogen formed?

Answer 14

at high temperatures

Question 15

What do particulates contain?

Answer 15

soot (carbon)

unburnt fuels

Question 16

What is complete combustion?

Answer 16

When there is plenty of oxygen, all the fuel burns

Question 17

What is partial combustion?

Answer 17

When there is not enough oxygen, some of the fuel does not burn

Question 18

When are carbon monoxide and particulates formed?

Answer 18

when there is partial combustion

Question 19

During combustion, the carbon and hydrogen in the fuels are…

Answer 19

oxidised

Question 20

What does sulfur dioxide and oxides of nitrogen cause?

Answer 20

acid rain

Question 21

What des carbon dioxide cause?

Answer 21

global warming

Question 22

What do particulates cause?

Answer 22

global dimming

Question 23

What is the impact of acid rain?

Answer 23

• Causes lakes to become acidic- plants and animals may die as a result
• Damages limestone buildings and stone statues

Question 24

Describe ways to reduce sulfur emissions

Answer 24

sulfur can be removed from fuels before they are burnt. eg- in vehicles.

Sulfur dioxide can be removed from the waste gases after combustion, eg- in powerstations

Question 25

Describe global dimming

Answer 25

Caused by particulates of soot that are produced when fossil fuels are burnt.

these particles reflect sun light back into space, which reduces the amount of sunlight that reaches earth’s surface.

Question 26

What are 3 biofuels?

Answer 26

Ethanol, Biodiesel, Hydrogen

Question 27

What is an advantage of using biofuels?

Answer 27

Carbon neutral and ‘clean’

Question 28

What are some negatives of using biofuels?

Answer 28

not widely available

ethanol and biodiesel could increase food prices

we can’t make enough to completely replace diesel

expensive to produce

Question 29

What is ethanol and biodiesel used for?

Answer 29

to run cars

Question 30

What are alkanes?

Answer 30

hydrocarbons

compounds of hydrogen and carbon atoms only

alkanes are saturated so only have single bonds

General formula is Cn H2n+2

Question 31

Name the type of reaction that releases energy from a fuel

Answer 31

exothermic

combustion

Question 32

Explain how petrol is separated from a mixture of hydrocarbons in crude oil

Answer 32

• By the process called fractional distillation
• crude oil is heated to about 350 degrees
• petrol evaporates to form a vapour and it rises up the column
• when petrol cools to its boiling point it condenses
• petrol has a relatively low boiling point and so is collected near the top of the fractionating column

Question 33

Why do most fuels used in car engines when burnt, the exhaust fumes contain nitrogen oxides?

Answer 33

nitrogen and oxygen in the air react in the hot engine to produce nitrogen oxides

Question 34

A mixture contains hydrocarbons with different boiling points

suggest a method of separating the mixture

Answer 34

fractional distillation

Question 35

Where does crude oil come from?

Answer 35

ancient biomass found in rocks

Question 36

What are biofuels produced from?

Answer 36

plant material

Question 37

In a fractionating column, the column is ……… at the bottom

Answer 37

hotter

Question 38

What is a fraction?

Answer 38

an area in a fractionating column where molecules collected have a similar boiling point as they have a similar number of atoms in their chain

Question 39

Why does burning fuels sometimes produce nitrogen oxides, even though the fuels contain no nitrogen

Answer 39

as at very high temperatures

nitrogen and oxygen in the atmosphere react