C1.4 Crude oil and fuels Flashcards
Crude oil is a mixture of a very large number of compounds. What does a mixture consist of?
2 or more elements or compounds NOT chemically combined together
What happens to the properties of compounds in a mixture and how can they be separated?
- Chemical properties of each substance are unchanged
- Separate by physical methods including distillation
What do most of the compounds in crude oil consist of?
Molecules made up of C and H (hydrocarbons)
Most of the hydrocarbons in crude oil are _____ hydrocarbons called _____, which have the general formula C_H____
Most of the hydrocarbons in crude oil are SATURATED hydrocarbons called ALKANES, which have the general formula»_space;CnH2n+2
How are the many hydrocarbons in crude oil separated and what are they separated into?
Separated by fractional distillation
Separated into fractions
What are the two main steps to fractional distillation?
- Evaporating the oil
- And allowing it to condense at different temps
What is a similarity of the hydrocarbons in crude oil?
And why do they boil at different temperatures?
- Each hydrocarbon contains molecules with SIMILAR numbers of carbon atoms
- Diff. temps BECAUSE OF the different number of carbon atoms
Describe the boiling points, viscosity and flammability of short chain molecules
- Low bpt.
- V. runny
- More flammable than long chains
Describe the boiling points, viscosity and flammability of long chain molecules
- High bpt.
- V. thick (VISCOUS)
- Less flammable, smoky flame
What do most fuels, including coal, contain? (2)
- Carbon and/or hydrogen
- May also contain some sulfur
When a fuel burns, what are some of the gases that are released? (5) -What substance other than gases could also be released? (1)
Carbon dioxide, Carbon monoxide
Sulfur dioxide, Oxides of nitrogen
Water (vapour)
-SOLID PARTICULATES may also be released
When does complete combustion happen,
and what is the important condition for forming oxides of nitrogen?
- When there is plenty of air
- High temperatures
Describe how particulates are formed in a diesel engine (3)
- Engine burns HYD.CAR.S with bigger molecules that petrol engines
- Big molecules react with oxygen, DON’T COMP. BURN
- Tiny particles (Soot, C and unburnt hyd.car.s) are produced
What happens to the carbon and hydrogen in the fuels?
They’re oxidised
How do these gases harm the environment?
(a) sulfur dioxide and oxides of nitrogen (b) carbon dioxide (c) solid particles
(a) acid rain
(b) global warming
(c) global dimming
