Topic 8 - Fuels And Earth Science Flashcards
What are hydrocarbons?
Compound that contains hydrogen and carbon atoms only
What is crude oil?
A complex mixture of hydrocarbons
Contains molecules with rings or chains of carbon atoms
An important source of useful substances like fuels and feedstocks for the petrochemical industry
A finite resource
Where can crude oil be found?
Under the sea and ground
What does it mean when crude oil is described as finite?
It will run out
How can crumped oil be separated?
Fractional distillation
How does the process of fractional distillation work to separate crude oil?
Crude oil is vaporised before it enters a fractionating column
The fractionating column is hotter at the bottom than at the top. The vapours rise up and condense at different fractions depending on their boiling points
Hydrocarbons with low boiling points will be tapped off the top of the column and hydrocarbons with high boiling points will be tapped off the bottom of the column
Why is crude oil separated?
Unseparated crude oil isn’t very useful but the separated products are very useful
Refinery gas is a fraction of crude oil. What are its common uses?
Heating and cooking
What fraction of crude oil is used as fuel in cars?
Petrol (gasoline)
Diesel is also less commonly used
Kerosene is a fraction of crude oil. What is common use of kerosene?
Aircraft fuel
Diesel oil is a fraction crude oil. What is it commonly used for?
Fuel for some cars and trains
Which fraction of crude oil is used for road surfacing and roofs?
Bitumen
Fuel oil is a fraction of crude oil. What is it commonly used for?
Fuel for large ships and in some power stations
How do the hydrocarbons at each faction differ?
Boiling points
Ease of ignition
Viscosity
The number of hydrogen and carbon atoms their molecules have
Where is the fractionating column do hydrocarbons with the highest viscosity condense?
They car collected at the bottom of the fractionating column
What are the properties of hydrocarbons that are tapped from the top of the fraction in column, like petrol and refinery gas?
Low boiling point
High volatile
Easily ignited
Shorter carbon chains
What is a homologous series?
Series of compounds which: Have the same general formula Have similar chemical properties Differ by CH2 in molecular formula form neighbouring molecules Slight variation in physical properties
Products from crude oil mostly belong to which homologous series?
Askance series
What are the only products when a hydrocarbon fuel undergoes complete combustion?
Water and carbon dioxide
Is energy given out when a fuel undergoes complete combustion?
Yes, it is exothermic
When does incomplete combustion occur? What is required to ensure complete combustion occurs?
Incomplete combustion occurs when there is an insufficient supply of oxygen
To ensure complete combustion occurs, the reaction should be carried out with excess oxygen
What are the products of incomplete combustion?
Carbon particles - soot
Carbon monoxide
Water
What are the problems with carbon monoxide?
Carbon monoxide is a toxic gas.
It is colourless and odourless and if breathed in can cause death
What are the problems with incomplete combustion?
Produces carbon monoxide with is toxic and can be fatal if breathed in
Produces carbon particulates which cause global dimming and respiratory problems
Why is sulphur dioxide sometimes produced when burning hydrocarbon fuels?
Some hydrocarbon fuels contain sulphur impurities . When the fuel is burned, the sulphur reacts with oxygen to form sulphur dioxide
How is acid rain produced?
Sulphur dioxide evaporated into the air, it reacts with water in the clouds to form sulphuric acid. This is acid rain.
What problems can acid rain cause?
Corrodes buildings and statues made of limestone
Kills/damages vegetation
Lowers pH of large bodies of water, killing wildlife
How are oxides of nitrogen produced from car engines?
The high temperature and pressure of a car engine causes nitrogen and oxygen from the air to react together
What problems are associated with oxides of nitrogen?
Pollutants
Produce acid rain with similar effects as SO2
Cause respiratory problems
What are the advantages of using hydrogen as fuel in cars?
It releases more energy per Kg compared to most other fuels
Water is the only product so no pollutants
Renewable source as hydrogen can be extracted from water
What are the disadvantages of using hydrogen as a fuel in cars?
It is expensive to produce and a lot of energy is required for the electrolysis of water to acquire the hydrogen
Difficult and dangerous to store hydrogen because it is very volatile and easily ignites
Name the non-renewable fossil fuel found in natural gas
Methane
Are petrol, kerosene and diesel renewable fuels?
No, they are non renewable
What is cracking?
Breaking down large hydrocarbons into smaller more useful ones
Saturated alkanes are cracked into shorter chain alkanes and short chain unsaturated alkanes
What do the terms saturated and unsaturated mean?
Saturated - only contains single bonds
Unsaturated - contains some c-c double bonds
What type of reaction is cracking?
Thermal decomposition
Why is cracking necessary?
The demand for shorter chain alkenes and alkanes is much greater than the demand for long chain alkanes
What produced the gases that formed earth’s early atmosphere?
Volcanic activity
Described how earth!s early atmosphere formed
Initially the Earth’s surface was molten with no atmosphere
Cooling caused land masses to solidify
Volcanoes formed on the land masses and released gases which formed the early atmosphere
What was the Earth’s early atmosphere thought to contain?
Little or no oxygen
Large amounts of carbon dioxide
Water vapour
Small amounts of other gases
How did oceans initially form?
Condensation of water vapour
How did the amount of carbon dioxide in the atmosphere decrease after oceans formed?
Carbon dioxide dissolved into the oceans so the amount of carbon dioxide in the atmosphere decreased
How did the amount of oxygen in the early Earth’s atmosphere increase?
The growth of early plants used carbon dioxide for photosynthesis and released oxygen. This increased the amount of oxygen and decreased the amount of carbon dioxide in the atmosphere.
What is the chemical test for oxygen?
Insert a glowing splint into a test tube of gas. If oxygen is present, the splint will ignite
What are greenhouse gases?
Various gases in the atmosphere that absorb the heat radiated from earth
What is the greenhouse effects?
Electromagnetic radiation from the sun passes through the Earth’s atmosphere
The earth absorbs some radiation and warms up
Heat is radiated from the earth as infrared radiation
Some of the infrared radiation is absorbed by greenhouse gases in the atmosphere which warms the atmosphere
How has human activity increased atmospheric carbon dioxide concentration?
Burning fossil fuels for energy releases carbon dioxide
Deforestation reduces the amount of photosynthesis occurring so less carbon dioxide is converted to oxygen
Evaluate the evidence that human activity is causing climate change
There is a correlation between carbon dioxide concentration in the atmosphere, fossil fuel consumption and temperature change
Correlation doesn’t mean causation
There may be uncertainties in the date
What is the current composition of Earth’s atmosphere?
Nitrogen - 78%
Oxygen - 21%
Argon - 0.93 %
Carbon - 0.04%
What are the effects of global warming?
Melting of polar ice caps Difficulties acquiring drinking water Flooding Forest fires Destruction of ecosystems
How has human activity increased the amount of methane in the atmosphere?
Raising livestock such as cows
Decay of organic waste in landfill sites
How can the effects of global warming be mitigated?
Construct flood defences in areas of low lying land
Use of irrigation systems to provide water in drought
Produce alternative crops which are better adapted to the new environment
