Fuels and Earth Science Flashcards
What type of resource is crude oil?
Non renewable
What is our main source of hydrocarbons?
Crude oil
What industry is crude oil used as a raw material in?
Petrochemical
How is crude oil formed?
Underground at high pressures and temperatures from the buried remains of plants and animals like plankton
What is crude oil a mixture of?
Different compounds that are not chemically combined
What are most of the carbons in crude oil?
Hydrocarbons
What do hydrocarbons contain?
Carbon and hydrogen
What are hydrocarbons in crude oil arranged in?
Chains or rings
Why can the properties of hydrocarbons change?
They differ in size
What process separates crude oil?
Fractional distillation
What is crude oil separated into during fractional distillation?
Groups of hydrocarbons with similar numbers of carbon atoms
What are the groups crude oil is separated into called?
Fractions
What are fractions?
Simpler, more useful mixtures of hydrocarbons that are similar lengths
What are short chain hydrocarbons?
Hydrocarbons with few carbon atoms
What are long chain hydrocarbons?
Hydrocarbons with lots of carbon atoms
What is the homologous series?
A series of compounds with the same general formular and similar chemical properties
What happens when carbon chains become longer?
The boiling point increases
As the alkane homologous series increases, how does the carbon number differ? How many does methane have?
Increases by one- methane has 1
As the alkane homologous series increases, how does the hydrogen number differ? How many does methane have?
By 2- methane has 4
As the alkene homologous series increases, how does the hydrogen number differ? How many does methene have?
Increases by 1- methene has 1
As the alkene homologous series increases, how does the hydrogen number differ? How many does methene have?
Increases by 2- methene has 2
What are the 2 different homologous series of hydrocarbons?
Alkanes and alkenes
What property of hydrocarbons affects which crude oil fraction it separates into?
Size
Why do all molecules in a fraction behave in the same way?
They have similar chemical properties
Why do smaller hydrocarbon molecules have lower boiling points?
Intermolecular forces of attraction break easier than in big molecules
What is viscosity?
How hard it is for a liquid to flow
What gives hydrocarbons a higher viscosity?
Stronger forces of attraction between molecules
What length hydrocarbons do fractions with a higher viscosity have?
Longer
What length hydrocarbons do fractions with a lower viscosity have?
Shorter
What length hydrocarbons are easier to ignite?
Shorter
Why are shorter hydrocarbons usually gases at room temperature?
Lower boiling point
Why are longer hydrocarbons harder to ignite?
Higher boiling points
What state are longer hydrocarbons at room temperature?
Higher boiling points
What properties do long chain hydrocarbons have?
Higher boiling points and viscosity
Less flammable
What properties do short chain hydrocarbons have?
Lower boiling points and viscosity
More flammable
What is cracking?
When longer chain hydrocarbons are broken down into shorter chain hydrocarbons
Why is cracking useful?
Long chain hydrocarbons are not as useful so are broken down into more useful, short chain hydrocarbons
What are the properties of alkane hydrocarbon molecules?
Long and saturated
What are the properties of alkene hydrocarbon molecules?
Smaller and unsaturated
What is a thermal decomposition reaction?
When one substance is broken down into at least 2 new ones when heated
Why do thermal decomposition reactions take lots of energy?
Strong covalent bonds are broken down
What are used to speed up thermal decomposition reactions?
Catalysts
When does cracking occur?
After fractional distillation- the longer molecules produced are cracked into smaller ones
Why does cracking occur?
More demand for products like petrol and diesel than bitumen and fuel oil
What are the two types of cracking?
Steam and catalytic
What occurs during steam cracking?
Heavy, vaporised hydrocarbons are mixed with steam under high temperatures
What occurs during catalytic cracking?
Vaporised long chain hydrocarbons are passed over a powdered catalyst at high temperatures and are broken apart
What catalyst is used for catalytic cracking?
Aluminium oxide
What does fractional distillation separate?
Hydrocarbons with different boiling points
What is the process of fractional distillation?
Crude oil heated and evaporates
Goes into fractionating column and rises
Temperature gradient means it is hotter at the bottom and cooler at the top
Long chain condense at the bottom
Short chain pass up column and condense at the top
What happens to the fractions collected after fractional distillation?
They are processed to make end products
Why do shorter chain hydrocarbons condense at the top?
Lower temperatures at the top and they have lower boiling points
What is bitumen used for?
Surfacing roads
What is fuel oil used for?
Larger ships and power stations
What is diesel oil used for?
Cars and trains
What is kerosene used for?
Fuel in aircraft
What are the refinery gases used for?
Domestic heating and cooking
Why are hydrocarbons great fuels?
When you burn them the complete combustion reactions give out lots of energy
Is complete combustion endothermic or exothermic?
Very exothermic
When hydrocarbons are burned in an excess of oxygen, what are the products?
Carbon dioxide and water
When does incomplete combustion take place?
When there is not enough oxygen for complete combustion
What are the products of incomplete combustion?
Carbon dioxide, carbon monoxide and water
In incomplete combustion, what is the carbon produced in the form of?
Soot
What is carbon monoxide?
A colourless, odourless, toxic gas
How does carbon monoxide lead to death?
It can combine with red blood cells to stop blood carrying oxygen around the body
What harmful gases are produced when fossil fuels are burned?
Sulfur dioxide, carbon dioxide and nitrous oxides
How is sulfur dioxide produced when burning fossil fuels?
Sulfur oxidises when burned
Why does sulfur dioxide fall as acid rain?
It mixes with clouds forming dilute sulfuric acid
How do nitrogen oxides form?
When hydrocarbons are burned in a confined space where the high temperatures cause nitrogen and oxygen to react, forming nitrogen oxides
Pros of hydrogen
Clean, renewable and no greenhouse gases emitted
Why is hydrogen clean?
Only waste product is water
Cons of hydrogen
Hard to store and must be manufactured which is expensive and not always clean
Why is hydrogen not always clean?
Needs to be manufactured which uses energy from another source eg from burning fossil fuels
Why is hydrogen hard to store?
Must be at high pressures
How long ago was the earth formed?
4.6 billion years ago
In the earth’s early existence (1st billion years) what did the volcanoes release via eruptions?
Carbon dioxide, steam, methane, ammonia and nitrogen
In the earth’s early existence (1st billion years) what gas was there little of in the atmosphere?
Oxygen
In the earth’s early existence (1st billion years) what was gradually building up in the atmosphere?
Nitrogen
In the earth’s early existence (1st billion years) what gas was there most of in the atmosphere?
Carbon dioxide
What condensed to form oceans?
Water vapour
What formed carbonate precipitates?
Carbon dioxide dissolved into oceans, forming a weak acid which reacted with seawater
What were carbon precipitates deposited as?
Sediment
What did some carbonate precipitates make?
Corals and shells of organisms
What removed carbon dioxide from the atmosphere?
Carbonate precipitates in the oceans which marine animals removed
Photosynthesis
What formed nitrogen gas?
Ammonia reacting with oxygen and was released by denitrifying bacteria
Why did nitrogen levels rise?
It isn’t very reactive so it wasn’t being broken down
What evolved after oceans?
Photosynthetic algae
What did algae remove and produce?
Carbon dioxide and oxygen
What did most of the carbon dioxide get locked up in?
Fossil fuels and sedimentary rocks
What evolved after algae?
Plants
Why did early organisms get killed off?
A build up of oxygen
What evolved after the early organisms?
More complex organisms that made use of oxygen
What did the oxygen create?
Ozone layer
Why did the ozone layer allow more complex organisms to evolve?
Blocked harmful rays from the sun
History of the earth (6)
1- volcanoes 2- oceans 3- nitrogen builds up 4- algae 4- complex organisms 5- ozone layer 6- more complex organisms
Distribution of gases in the earth’s atmosphere today
Nitrogen = 78%
Oxygen = 21%
Other gases = 1%
What does the greenhouse effect do?
Keeps us warm
Describe the greenhouse effect
Sun emits electromagnetic radiation which passes through atmosphere
Short wavelength radiation absorbed by earth, warming us up
Some is radiated as longer wavelength, infrared radiation
Some infrared radiation is absorbed by greenhouse gases
Some is reflected back to Earth because the greenhouse gases don’t let the long wavelengths pass through
Trapped in the atmosphere, keeping us warm
Some re-emitted back into space
Why does the enhanced greenhouse effect occur?
If the concentration of greenhouse gases increases because more solar radiation is absorbed and less is re-emitted into space which causes the atmosphere to warm up
What has produced more greenhouse gases?
Human activity
What is global warming?
Average global temperatures increasing due the enhanced greenhouse effect
What is global warming a type of?
Climate change
What does global warming cause?
Other types of climate change like changing rainfall patterns and the melting of ice caps which causes flooding
What is anthropogenic?
Caused by humans
3 main greenhouse gases
Water vapour, carbon dioxide, methane
How do carbon dioxide levels increase?
Burning fossil fuels
How do methane levels increase?
Agriculture- growing rice in flooded fields or digestive processes of certain livestock
Why is less carbon dioxide removed from the atmosphere?
Deforestation means cutting down and burning trees which releases more carbon dioxide and prevents it being absorbed
What human activities are causing climate change?
Agriculture, deforestation, land fill sites, burning fossil fuels
How are land fill sites causing climate change?
More mounds of decomposing waste releases methane
What could cause rising sea levels, leading to flooding and erosion of coastal regions?
Melting polar ice sheets and glaciers
Meteorological effects of climate change
Higher frequency and severity of storms, heatwaves and droughts
How would the amount of water change due to climate change?
Availability would change
What would there be shortages of due to climate change?
Food
What could increasing temperatures change the distribution of?
Animals
Ways to estimate climate change
Fossils, tree rings, gas bubbles trapped in ice cores, pollen
