Topic 8 - Fuels and Earth Science✅

What are hydrocarbons

Compounds that contain only carbon and hydrogen

What is crude oil (structure)

Crude oil is

• A complex mixture of hydrocarbons

• Containing molecules in which carbon atoms are in chains

What is crude oil (irl)

• A finite resource

• An important source of useful substances e.g. Fuels

How is crude oil separated simpler, more useful mixtures

By fractional distillation

• The column at the top is the coldest and the column at the bottom is the hottest

• The vapours rise through the column and cool down

• The vapours condense when they reach a part of the column that is cool enough

• The liquid falls into a tray and is piped away

• The vapours with the lowest boiling point do not condense at all, and leave the top as a mixture of gases

• Bitumen has the highest melting point, and leaves the bottom as a liquid

Properties of small hydrocarbons

• Low boiling point

• Flammable

• Clean flame

• Not very viscous

Properties of large hydrocarbons

• High boiling point

• Not that flammable

• Not that clean of a flame

• Viscous

Mnemonic for crude oil fractions

Great Players Keep Dominating For Bruins

What are the fractions of crude oil

• Gas

• Petrol

• Kerosene

• Diesel oil

• Fuel oil

• Bitumen

Use of gas

Domestic heating and cooking

Use of petrol

Fuel for cars

Use of kerosene

Aircraft fuel

Use of diesel oil

Fuel for some cars and trains

Use of fuel oil

Fuel for large ships

Use of bitumen

Surfacing roads

What is a homologous series

A series of compounds which:

• Have the same general formula

• Differ by CH2 in molecular formula

• Show a gradual variation in physical properties e.g. Boiling point

• Have similar chemical properties

Describe the complete combustion of hydrocarbons

A reaction in which

• Carbon dioxide and water are produced

• Energy is given out

What does the incomplete combustion of hydrocarbons produce

• Carbon

• Carbon monoxide

How does the incomplete combustion of carbon produce carbon and carbon monoxide

• Carbon

• Carbon monoxide

How does the incomplete combustion of carbon produce carbon and carbon monoxide

• If there's not enough oxygen, some of the fuel doesn't burn (partial combustion)

• Here, solid particles of soot (carbons) and unburnt fuel are released.

• Carbon monoxide (CO) is also released when there isn't enough oxygen to produce CO2

How does carbon monoxide behave as a toxic gas

• It is a colourless and odourless gas

• When breathed in, it stops red blood cells from carrying oxygen around your body

• This leads to death

Problems of carbon monoxide and soot

• Carbon monoxide causes health problems

• Soot causes global dimming

Explain how impurities can result in acid rain

• Sulfur is present as an impurity

• When fuel burns, it reacts with oxygen

• Forming sulfur dioxide

• Sulfur dioxide dissolves in rain

Problems associated with acid rain

• Damages buildings and statues made of limestone

• Reduces the growth of trees and crops

• Lowers the pH of water in lakes, killing fish

Explain why oxygen and nitrogen react together to produce oxides of nitrogen

• When fuels are burned in engins, oxygen and nitrogen react together at high temperatures to produce oxides of nitrogen

• Nitrogen and oxygen from the air combine, producing nitrogen monoxide

• When nitrogen monoxide is released from vehicles, it combines with oxygen in the air to form nitrogen dioxide

• Nitrogen monoxide and nitrogen dioxide are pollutants

Advantages of using hydrogen as fuel in cars

• Petrol is a finite resource so it's better to use hydrogen

• Hydrogen only produces water - no carbon dioxide

Disadvantages of using hydrogen as fuel in cars

• Expensive

• Difficult to transport and store hydrogen

• Dangerous as hydrogen can be explosive

What are petrol, kerosene, and diesel oil and how are they obtained

• Non renewable fossil fuels

• Obtained from crude oil

What is methane

• A non renewable fossil fuel

• Found in natural gas

What is the main reason of cracking

• To break down larger saturated hydrocarbons (alkanes) into smaller more useful ones

• Some of these smaller ones are unsaturated (alkenes)

Explain the process of cracking

• Hydrocarbons can be cracked to produce smaller, more useful molecules

• This process involves heating hydrocarbons to vaporise them

• The vapours are mixed with steam and heated to a very high temperature so that thermal decomposition reactions can occur

Two products of cracking

Alkanes and alkenes

What makes a hydrocarbon unsaturated

Double bond

General formula of alkenes

C_nH_2n

General formula of alkanes

C_nH_2n+2

Explain why cracking is necessary

• Demand for smaller chained alkanes is much greater than for longer chained alkanes

• Shorter chained hydrocarbons ignite more easily - so are more useful as fuels

What formed the early atmosphere

Gases produced by volcanic activity

What was the Earth's early atmosphere thought to contain

• Little or no oxygen

• A large amount of carbon dioxide

• Small amounts of other gases

How did the condensation of water vapour form oceans

• Water vapour condensed to form oceans

• This happened when the earth cooled

Explain how the amount of carbon dioxide in the atmosphere decreased

• CO2 dissolved in the water and carbonates were precipitated, producing sediments

• Marine life used carbonates to make their shells and skeletons

• Green plants and algae absorbed amounts of carbon dioxide when they photosynthesised

• When these organisms died, their remains locked the atmospheric carbon into the rocks

• All of this reduced the amount of CO2 in the atmosphere

Explain how plants increased the amount of oxygen in the atmosphere

• Algae and plants absorb carbon dioxide and turn it into oxygen

• 2.7 billion years ago, algae first started producing oxygen

• Over the next billion years, the amount of oxygen in the atmosphere gradually increased, allowing animals to evolve

• Algae and plants also decrease the level of CO2 in the atmosphere

What is the test for oxygen

• Insert a glowing splint into a test tube of gas

• It will relight if the gas is oxygen

How do various gases in atmosphere absorb heat radiated from the earth

• Electromagnetic radiation from the sun passes though the Earth's atmosphere

• The Earth absorbs some radiation and warms up

• Some heat is radiation from earth, and absorbed by greenhouse gases

• The atmosphere warms up - this is the greenhouse effect

How does the change in atmospheric CO2 relate to temperature change

• Increasing CO2 levels correlate with rising global temperatures

• Due to the greenhouse effect

How does fuel consumption contribute to climate change

• Burning fossil fuels releases CO2

• This increases the greenhouse effect

What evidence supports the claim that humans are causing climate change

Rising CO2 levels have occurred from industrial activity

Why do measurement locations affect climate data accuracy

Urban areas may show artificially high temperatures due to the urban heat island effect

What factors affect the accuracy of historical climate data

• Older data comes from indirect sources

• E.g. Ice cores and tree rings

• Which may have limitations in precision compared to modern techniques

Describe the composition of today's atmosphere

• 78% nitrogen

• 20% oxygen

• 0.9% argon

• 0.04% carbon dioxide

What actions cause increased levels of carbon dioxide and methane

• Driving

• Raising livestock

• Decay of organic waste in landfill sites

• Consuming electricity

How do carbon dioxide and methane contribute to climate change

• They trap heat in the atmosphere

• Increasing the greenhouse effect

Consequences of climate change

• Rising sea levels

• Extreme weather e.g. Droughts

• Habitat destruction

How can we reduce greenhouse gas emissions

• Using renewable energy

• Reducing fossil fuel use

• Planting trees