fuels and earth science Flashcards
What are hydrocarbons
Compounds that contain hydrogen and carbon only
What is crude oil
- a complete mixture of hydrocarbons
- containing molecules in which carbon atoms are in chains or rings
- an important source of useful substances
- a finite resource
How can you separate crude oil into simpler and more useful mixtures by fractional distillation
- The oil is heated until most of it has turned into a gas and the gases enter a fractionating column
- in the column there is a temperature gradient, the longer hydrocarbons have higher boiling points. They turn back into liquids and drain out of the column early on when they’re near the bottom. The shorter carbohydrates have lower boiling points. They tend to liquid and drain out much later on to the top of the column where it’s cooler.
- each fraction contains a mixture of hydrocarbons mostly alkalenes with similar boiling points
What is the fraction, gas, used for?
Used in domestic heating and cooking
What is the fraction, petrol, used for?
Fuel for cars
What is the fraction, kerosene, used for?
Use as fuel for aircraft
What is the fraction, diesel oil, used for?
used for fuel for some cars and trains
What is the fraction, fuel oil, used for?
Used as fuel for large ships and in some power stations
What is the fraction, bitumen, used for?
Used to surface roads and roofs
How hydrocarbons in different fractions differ from each other regarding boiling points
- Big molecules have higher boiling points in small molecules do this because it takes a lot of energy and force of attraction to break the bonds
How hydrocarbons in different fractions differ from each other regarding ease of ignition
Short hydrocarbons are easy to ignite because they have lower boiling points so tend to be gases at room temperature
- these gas molecules mixed with oxygen in the air to produce a gas mixture which burst into flames if it comes into contact with a spark
- longer hydrocarbons are usually liquid liquids at room temperature they have higher boiling points in a much harder to ignite
How hydrocarbons in different fractions differ from each other regarding viscosity
- viscosity measures how easily a substance flows
- The stronger the force is between the hydrocarbon molecules the harder is for the liquid to flow
- longer hydrocarbons have a higher viscosity so they’re thick
How hydrocarbons in different fractions differ from each other regarding number of carbon and hydrogen atoms their molecules contain
As it gets cooler, the number of carbons in the hydrocarbon in that fraction is lower
- in gases, there may be -3 carbons in the hydrocarbon
- in between there is approximately 70+ number of carbons in the hydrocarbons
What are hydrocarbons in different fractions members of
Alkane homologous series
What is the homologous series as a series of compounds which:
- have the same general formula
- differ by CH2 in molecular formulae from neighbouring compounds
- show a gradual variation in physical properties, as exemplified by their boiling points
- have similar chemical properties
What is produced and given out in a complete combustion of hydrocarbon fuels as a reaction
Carbon dioxide and water is given out
Energy is given out
What is incomplete combustion
Occurs when a hydrocarbon burns in a limited supply of oxygen
What happens during incomplete combustion
Tiny particles of carbon can be released into the atmosphere
When they fall back to the ground, they deposit themselves as soot
Why is carbon monoxide a toxic gas?
Carbon monoxide can combine with red blood cells and stop your blood from carrying oxygen around the body
- a lack of oxygen in the blood supply to the brain and need to fainting, a coma or even death
What can impurities in hydrocarbon fuels result in
Sulfur dioxide
How can sulphur dioxide cause acid rain?
When sulphur dioxide mixes with cloud clouds, it forms sulphuric acid this then falls as acid rain
How do oxygen and nitrogen produce pollutants when reacted together at high temperatures?
Nitrogen oxide are created from a reaction between the nitrogen and oxygen in the air, caused by the energy released by combustion reaction
Nitrogen oxide can contribute to acid rain and that ground level can cause photochemical smog
What are advantages of using hydrogen rather than petrol as a fuel in cars?
- It’s a very clean fuel
- only waste product is water
- renewable resource
What are disadvantages of using hydrogen rather than petrol as fuel in cars?
- need a special, expensive engine
- uses energy from another source
- hydrogen is hard to store and not widely available
What is kerosene, petrol, and diesel oil?
Non-renewable fossil fuels obtained from crude oil
What is methane?
Non-renewable fossil fuel found in natural gas
How does cracking happen?
- Breaks down larger, saturated hydrocarbon molecules into smaller, more useful ones some of which are unsaturated
- when one substance breaks down into at least two new ones when you heat it- this means breaking strong covalent bonds you need lots of energy
Why is cracking necessary?
It produces lots of alkenemolecules which can be used to make polymers
What did the gases produced by volcanic activity form?
The earths early atmosphere
What does the earths early atmosphere was thought to contain?
- Little or no oxygen
- A large amount of carbon dioxide
- Water vapour
- Small amount of other gases
How does condensation of water vapour form oceans?
The Earth called down and this caused water vapour to condense and fall to make oceans
How did the amount of carbon dioxide in the atmosphere decrease when carbon dioxide dissolved as the oceans formed?
Really fast
How the growth of primitive plants used carbon dioxide and released oxygen by photosynthesis and consequently the amount of oxygen in the atmosphere gradually increased
The amount of oxygen in the air gradually built up and much of the carbon dioxide eventually got locked up in fossil fuels and sedimentary rocks
Chemical test for oxygen
Check if the gas will relight a glowing splint
What is the greenhouse effect?
Various gases in the atmosphere, including carbon dioxide, methane and water vapour, absorb heat radiated from the Earth, subsequently releasing energy which keeps the Earth warm
As the years increase percentage of carbon dioxide in the atmosphere increases
What is the composition of today’s atmosphere?
78% nitrogen and approximately 21% oxygen
Small amounts of other gases, mainly carbon dioxide, noble gases and water vapour
What are the potential effects on the climate of increased levels of carbon dioxide and methane generated by human activity, including burning fossil fuels and livestock farming?
Global warming is a type of climate changing causes other types of climate change
it can cause severe flooding to the polar ice caps melting
