crude oils and fuels Flashcards

1
Q

what are crude oils

A
  • finite resource found in rocks
  • thick black oil used to make many everyday objects
  • mixture of many compounds
  • almost all compounds are hydrocarbons
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2
Q

what are hydrocarbons

A

a compound made entirely of hydrogen and carbon atoms

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3
Q

what are alkanes

A

compounds that consist entirely of single-bonded carbon and hydrogen atoms (saturated hydrocarbons)
- formula = C(n)H(2n+n)

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4
Q

what are fractions

A

substances in crude oil that similar boiling points

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5
Q

properties of alkanes

A

depends on amount of carbon atoms, as chain lengths increase alkanes become:
- more viscous
- less volatile
- less flammable
- boiling points increase

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6
Q

why do properties change based on chain lengths

A

large molecules have stronger intermolecular forces and become harder to separate

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7
Q

what is fractional distillation

A

a method of separating crude oil, boils and puts hydrocarbons of similar chain lengths into the same tray

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8
Q

method of fractional distillation

A

1) crude oil is vaporised and pumped into the bottom of a fractioning column (hot at bottom, cool at top)
2) the gasses rise and cool whilst doing so
3) when the temperatures drop enough they condense
4) the longest chains condense almost immediately and collect at the bottom, the short chains condense at lower temperatures and collect near the top
5) the liquid fractions are collected

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9
Q

examples of hydrocarbons with different chain lengths

A

long chains - tar, grease and lubricants
short chains - petrol
- short chains are more useful in everyday life but are less common to find in crude oil

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10
Q

what is cracking

A

a method to break long chains into smaller chains

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11
Q

different types of cracking

A
  • catalytic
  • steam
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12
Q

catalytic cracking

A
  • catalysts known as zeolite (contains aluminium oxide and silicone oxide)
  • zeolite catalysts are man made and expensive
  • approximately 550 degrees
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13
Q

steam cracking

A
  • heated over 800 degrees
  • mixed with steam
  • no catalyst needed, less expensive
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14
Q

what are alknenes

A

similar to alkanes but contain a carbon to carbon double bond, have less hydrogen atoms
- formula = C(n)H(2n)

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15
Q

what is combustion

A

the chemical name for burning hydrocarbons
- involves reacting with oxygen and releases large amounts of energy

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16
Q

complete combustion

A

when there is an abundance of oxygen, more than needed
-hydrocarbon + O2 = H2O + CO2

17
Q

incomplete combustion

A

when there is a limited amount of oxygen
- hydrocarbon + O2 = H2O + CO