CHAPTER 9 CRUDE OILS AND FUELS Flashcards
What are Hydrocarbons
A chemical compound what only contains Hydrogen and Carbon only
What are alkanes,alkenes and alkynes
Alkanes - saturated hydrocarbons single bond
Alkenes - unsaturated hydrocarbons double bond
Alkynes - unsaturated hydrocarbons triple bond
4 hydrocarbons (alkanes) and their chemical formula and what their prefix represents
Methane - CH4 (meth - 1 carbon atoms)
Ethane - C2H6 (eth - 2 carbon atoms)
Propane - C3H8 (prop - 3 carbon atoms)
Butane - C4H10 (but - 4 carbon atoms)
How is coal formed what is its composition and what is it uses
Formed from heat and pressure over millions of years. Made of carbon and is used for generating electricity
How is oil formed what is its composition and what is it uses
Formed from plankton from heat and pressure with anaerobic bacteria over millions of years. Made of mixtures of hydrocarbons and is used for fuels and making plastics
How is gas formed what is its composition and what is it uses
Formed from plankton from heat and pressure with anaerobic bacteria over millions of years. Made mainly of methane and used for heating and cooking
What is crude oil
A mixture of hydrocarbons of different lengths
What are alkanes (proper def)
Saturated hydrocarbons with the general formula CnH2n+2
What is a homologous series
A family of hydrocarbons
How can you describe the size of molecules/hydrocarbons
Long or short chain
What is volatility,viscosity and flammability
Volatility - the tendency to to turn into a gas
Viscosity - how easily it dlows
Flammability - how easily it burns
What happens to the bonds during fractional distillation
The strong chemical bonds aren’t broken whereas the weak intermolecular forces are broken
What is fractional distillation of oil
Where crude oil is distilled and the evaporated components are collected as they condense at different temperatures
What happens at the different levels at fractional distillation (5)
- At 350 gas condenses to residue which is long chain hydrocarbons used for making roads (bottom of tower)
3.level above gas condenses to diesel oil/gas oil which is used as fuel in diesel engines
4.level above gas condenses to kerosene which is used for aircraft fuel
5.level above gas condenses to gasoline/petrol which is used for fuel in car engine
6.At the top level at 50 gas condenses to refinery/petroleum gas which are short chain hydrocarbons and low boiling point alkanes used as fuel
Why do longer chain hydrocarbons have higher boiling points
They have a larger molecule mass and have stronger bonds between molecule. So the stronger they are the higher the boiling point as more energy is needed to overcome the larger forces
What happens during fractional distillation (3)
- Crude oil is heated in a furnace and passed into the bottom of a fractionating column. The vapour mixture given off rises up the column and the different fractions converts out at different parts of the column
- The fractions at the top are light coloured runny liquids whereas the fractions at the bottom are dark and treacle like.
- The components present in crude oil separate because they have different boiling points.
What is combustion
An oxidation(looses electrons) chemical reaction where energy is released from fuels. Hydrocarbon fuels react with oxygen to produce carbon dioxide and water when there is a plentiful supply of oxygen
What happens when there isn’t enough oxygen in combustion
Its incomplete combustion and the products are carbon monoxide and water when there
What are the tests to see if combustion is positive (for water and carbon dioxide)
Water: To use Cobalt chloride paper what turns from blue to pink
Carbon dioxide: Bubble it though limewater then it turns cloudy
What is cracking and what type of reaction is it
Where large hydrocarbons are broken down into smaller more useful hydrocarbons. Its thermal decomposition.
What happens during cracking
Fractions containing large hydrocarbons are vaporised and passed over a hot catalyst of aluminium oxide. Which breaks chemical bonds in the molecules and forms smaller hydrocarbons molecules.
Why is cracking done
As long chain hydrocarbons of crude oil are not in demand while the lighter fractions are so they crack them down to get more supply
