crude oils and fuels

Question 1

what are crude oils

Answer 1

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

Question 2

what are hydrocarbons

Answer 2

a compound made entirely of hydrogen and carbon atoms

Question 3

what are alkanes

Answer 3

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

Question 4

what are fractions

Answer 4

substances in crude oil that similar boiling points

Question 5

properties of alkanes

Answer 5

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

Question 6

why do properties change based on chain lengths

Answer 6

large molecules have stronger intermolecular forces and become harder to separate

Question 7

what is fractional distillation

Answer 7

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

Question 8

method of fractional distillation

Answer 8

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

Question 9

examples of hydrocarbons with different chain lengths

Answer 9

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

Question 10

what is cracking

Answer 10

a method to break long chains into smaller chains

Question 11

different types of cracking

Answer 11

• catalytic
• steam

Question 12

catalytic cracking

Answer 12

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

Question 13

steam cracking

Answer 13

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

Question 14

what are alknenes

Answer 14

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

Question 15

what is combustion

Answer 15

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

Question 16

complete combustion

Answer 16

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

Question 17

incomplete combustion

Answer 17

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