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What is a hydrocarbon?
Compounds containing hydrogen and carbon only
What is crude oil?
A complex mixture of hydrocarbons, which contains rings/chains of carbon atoms, used in industry but is a finite resource
How does fractional distillation work to separate crude oil?
It is vapouriest before it enters the fractional column, which is hotter at the bottom and cooler at the top. Vapour rises and condenses at different fractions depending on their boiling points - hydrocarbons with low boiling points will be tapped off at the top of the column, whereas hydrocarbons with high boiling points will be tapped off at the bottom of the column
What is the use of refinery gas?
In domestic heating and cooking
What is petrol used for?
In fuel for cars
What is kerosene used for?
In fuel for aircraft
What is diesel oil used for?
In fuel for some cars and trains
What is fuel oil used for?
In fuel for large ships, and may be used in powerstations
What is bitumen used for?
Surfacing roads and roofs
What is the trend in boiling point as hydrocarbon chain length increases?
As the chain length increases, the boiling point increases
What is the trend in viscosity as hydrocarbon chain length increases?
As chain length increases, viscosity increases
What is the trend in ease of ignition as hydrocarbon chain length increases?
As chain length increases, the ease of ignition decreases (it becomes harder to light on fire)
What homologous series do the fractions of crude oil belong to?
The alkane homologous series
What is a homologous series?
They have the same general formula, they differ by CH2 in molecular formulae from neighbouring compounds, with a gradual variation in physical properties and similar chemical properties
What are the products when a hydrocarbon undergoes complete combustion?
Water and carbon dioxide
Why does incomplete combustion occur?
It occurs due to lack of oxygen
What are the products of incomplete combustion of hydrocarbons?
It produces carbon monoxide and carbon
Why is carbon monoxide toxic?
It prevents red blood cells from carrying oxygen by binding to haemoglobin, which can cause death
What are the problems with incomplete combustion?
It produces carbon monoxide which is toxic, and produces soot which can cause respiratory problems and global dimming
Why is sulfur dioxide sometimes produced when burning hydrocarbons?
Hydrocarbons may contain sulfur impurities. Sulfur reacts with oxygen to form sulfur dioxide
How is acid rain produced?
Sulfur dioxide evaporates into the air and reacts with water in clouds to form sulfuric acid
What are the problems with acid rain?
It corrodes buildings, damages vegetation, and lowers the pH of bodies of water which can kill wildlife
How are oxides of nitrogen formed from car engines?
High temperature and pressure causes nitrogen and oxygen in the air to react, creating pollutants
What are the advantages of using hydrogen as fuels in cars?
It releases more energy compared to most fuels, it releases no pollutants (the only product is water), and it is a renewable source
What fossil fuels are obtained from crude oil?
Kerosene, diesel and petrol
What is the fossil fuel found in natural gas?
Methane
What is cracking?
Breaking down large hydrocarbons into smaller, more useful ones. Saturated alkanes are cracked into shorter chain alkanes and short chain unsaturated alkenes
Why is cracking necessary?
The demand for shorter chain alkanes and alkenes is greater than the demand for long chain alkanes
What did the gases from volcanic activity form?
Earth’s early atmosphere
What was the early atmosphere thought to have contained?
Little to no oxygen, large amounts of carbon dioxide, water vapour, small amounts of other gases
How did the oceans form?
Condensation of water vapour in the atmosphere
How did the amount of oxygen in the atmosphere increase?
Growth of early plants used carbon dioxide for photosynthesis and released oxygen
Chemical test for oxygen
A glowing splint put into a test tube of oxygen will relight itself
What is the greenhouse effect?
Radiation from the sun passes through Earth’s atmosphere. Earth absorbs some radiation and warms up. Heat is radiated from Earth as infrared radiation. Some infrared radiation is absorbed by greenhouse gases in the atmosphere, warming it up
How has human activity increased atmospheric carbon dioxide concentration?
Burning fossil fuels releases carbon dioxide, deforestation reduces the amount of photosynthesis, so less carbon dioxide is converted into 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. However, there may be uncertainties in the data
What is the current composition of the Earth’s atmosphere?
Nitrogen (78%), oxygen (21%), argon (less than 1%), carbon dioxide (0.04%)
What are the effects of global warming?
Melting polar ice caps, flooding, forest fires, destruction of ecosystems
How can the effects of global warning be mitigated?
By constructing flood defences in low lying areas, the use of irrigation to provide water in droughts, producing alternate crops which are adapted to the new environment
