Fuels and Earth Science (2)

Question 1

What is

crude oil?

Answer 1

a complex mixture of many different hydrocarbons

that is also a finite resource

Question 2

What are

hydrocarbons?

Answer 2

compounds that contain only hydrogen and carbon

Question 3

How is

crude oil formed?

Answer 3

it is formed at high temperatures and pressures from the remains of animals and plants that died millions of years ago

Question 4

What are

fractions?

Answer 4

simpler, more useful mixtures than crude oil

these contain groups of hydrocarbons of similar lengths

Question 5

What occurs during the

fractional distillation of crude oil?

(intro + 6 steps)

Answer 5

The crude oil is split into separate fractions.
1. The crude oil is heated so that most of it evaporates.
2. It is then pumped into the bottom of a piece of equipment known as a fractionating column. (This fractionating column has a temperature gradient running through it - hottest at the bottom and coldest at the top.)
3. The liquid part (bitumen) is drained off.
4. The gas rises up the column and gradually cools.
5. Different compounds in the mixture have different boiling points, so they condense at different temperatures. This means that they condense at different levels in the fractionating column.
6. The various fractions are constantly tapped off from the column at the different levels where they condense.

Hydrocarbons that have a similar number of carbon atoms have similar boiling points, so they condense at similar levels in the column.

Question 6

What is the fraction

bitumen

used for?

Answer 6

surfacing roads and the roofs of buildings

Question 7

What is the fraction

fuel oil

used for?

Answer 7

as fuel for large ships and in some power stations

Question 8

What is the fraction

diesel oil

used for?

Answer 8

as a fuel in some cars and larger vehicles, such as trains

Question 9

What is the fraction

kerosene

used for?

Answer 9

as fuel in aircraft

Question 10

What is the fraction

petrol

used for?

Answer 10

as fuel in cars

Question 11

What is the fraction

gases

used for?

Answer 11

domestic heating appliances and cooking

Question 12

Define

homologous series.

Answer 12

a family of molecules which have the same general formula and share similar chemical properties

Question 13

What is the relationship between

hydrocarbon boiling point and chain length?

and why?

Answer 13

As chain length increases, so does boiling point.

This is because the intermolecular forces of attraction break a lot more easily in small molecules than they do in bigger molecules.

A large molecule contains many points along its length where it can be attracted to another molecule. So, even if it can overcome these forces at a few points along its length, it’s still got lots of other places where the force is still strong enough to hold it in place.

Question 14

What is the relationship between

hydrocarbon ease of ignition and chain length?

and why?

Answer 14

As chain length increases, ease of ignition decreases.

This is because shorter hydrocarbons have lower boiling points and tend to be gases at room temperature. These gas molecules mix with oxygen in the air to produce a gas mixture that will burts into flames if it comes into contact with a spark.

Question 15

What is

viscosity?

Answer 15

how easily a substance flows

Question 16

What is the relationship between

hydrocarbon viscosity and chain length?

and why?

Answer 16

As chain length increases, viscosity decreases.

This is because the stronger the intermolecular forces between hydrocarbon molecules, the harder it is for the liquid to flow.

Question 17

What is the general equation for

complete combustion of hydrocarbons?

Answer 17

hydrocarbon + oxygen -> carbon dioxide + water

Question 18

When do

hydrocarbons undergo incomplete combustion?

Answer 18

when they are burned with insufficient oxygen in the air

Question 19

What other products are produced in

incomplete combustion?

Answer 19

carbon monoxide and sometimes carbon (in the form of soot)

Question 20

Why is

carbon monoxide a health hazard?

Answer 20

It binds to the haemoglobin in your red blood cells that normally carry oxygen - so less oxygen is able to be transported around your body. A lack of oxygen in the blood supply to the brain can lead to fainting, a coma or even death.

Question 21

What are the negatives of

soot?

Answer 21

• makes buildings look dirty
• reduces air quality
• can cause or worsen respiratory problems

appliances that produce soot are inefficient as well as dangerous

Question 22

What

harmful substances does the burning of fossil fuels release?

(3)

Answer 22

• carbon dioxide gas
• sulfur dioxide
• various nitrogen oxides

Question 23

What is the problem with

sulfur dioxide gas?

and where does it come from?

Answer 23

It mixes with water in the clouds and reacts with them to form dilute sulfuric acid. This then falls as acid rain.

this comes from the burning of sulfur impurities

Question 24

What are the negatives of

acid rain?

(5)

Answer 24

• causes lakes to become acidic (causing many plants and animals to die)
• kills trees
• damages limestone buildings
• ruins stone statues
• can make metals corrode

Question 25

# What are the negatives of nitrogen oxides? | (2) and where do they come from?

Answer 25

- contribute to acid rain - cause photochemical smog ## Footnote At high temperatures reached inside combustion engines, the nitrogen and oxygen in the air can react to form nitrogen oxides.

Question 26

# What are some advantages of hydrogen fuel cells? | (3)

Answer 26

- the only waste product is water - no harmful pollutants are produced - hydrogen is obtained from water which is a renewable resource

Question 27

# What are some disadvantages of hydrogen fuel cells? | (4)

Answer 27

- a special, expensive engine is required - hydrogen gas needs to be manufactured - which is expensive and often use non-renewable energy - hydrogen is a highly flammable gas - so it is hard to store safely - hydrogen is not widely available - which can make it more expensive to purchase than regular fuels

Question 28

# What is thermal decomposition?

Answer 28

breaking molecules down into at least two new ones by heating them

Question 29

# What type of reaction is cracking? | and what does it involve?

Answer 29

a type of thermal decomposition | involves breaking longer alkanes into smaller, more useful hydrocarbons

Question 30

# What are the conditions for cracking?

Answer 30

- aluminium oxide (alumina) catalyst - temperatures of 400-700°C - a pressure of 70 atmospheres

Question 31

# Describe the process of cracking. | (3 steps)

Answer 31

1. The alkane is heated until it is vaporised. 2. It is then passed over the catalyst. 3. When it comes into contact with the alumina, it breaks, producing a mixture of short-chain alkanes and alkenes.

Question 32

# What was Earth like for the first billion years? | (4 key points) ## Footnote - activity? - early atmosphere?

Answer 32

- there was instense volcanic activity - the volcanoes gave out a lot of gas - the early atmosphere contained carbond dioxide with little or no oxygen - volcanic activity released nitrogen, water vapour, methane and ammonia which would have built up over time

Question 33

# How was most of the carbon dioxide in the early atmosphere removed?

Answer 33

- absorption by the oceans - absorption by plants and algae

Question 34

# What is the word equation for photosynthesis? | and what is the symbol equation?

Answer 34

carbon dioxide + water -> glucose + oxygen | 6CO2 + 6H2O -> C6H12O6 + 6O2

Question 35

# Describe a test for oxygen gas.

Answer 35

1. Collect the gas in a test tube. 2. Put a glowing splint into the test tube. 3. If oxygen gas is present, the splint will relight.

Question 36

# What are some examples of greenhouse gases? | (3)

Answer 36

- carbon dioxide - methane - water vapour

Question 37

# Describe the greenhouse effect. | (4 steps)

Answer 37

1. The sun emits short wavelength EM radiation which passes through the Earth's atmosphere. 2. The Earth's surface absorbs this and re-emits it as long wavelength IR radiation. 3. This radiation is absorbed by greenhouse gases in the atmosphere and re-radiated out in all directions - including back towards Earth. 4. This warms the surface of the Earth.

Question 38

# What is the current composition of the Earth's atmosphere?

Answer 38

78% nitrogen 21% oxygen some carbon dioxide, noble gases and water vapour

Question 39

# What key areas of human activity have increased greenhouse gases? | (3)

Answer 39

- increased energy consumption - deforestation - methane and farming

Question 40

# What are some negative consequences of climate change? | (4)

Answer 40

- polar ice caps and glacier could melt - flooding in coastal areas will rise (as well as coastal erosion) - changes in rainfall patterns may cause some regions to get too much or too little water - the frequency and severity of storms may increase