Crude oil and alkanes

• What is crude oil primarily composed of?

  A mixture of different hydrocarbons
• What process is used to separate hydrocarbons by carbon chain length?

  Fractional distillation
• Why are shorter hydrocarbons considered better fuels?

  They are more flammable
• What is the purpose of cracking in hydrocarbons?

  To break down long hydrocarbons into shorter ones
• What type of reaction is cracking?

  Thermal decomposition reaction
• What does thermal decomposition mean?

  Breaking down molecules by heating
• What are the two methods of cracking?

  Catalytic cracking and steam cracking
• What is the first step in both catalytic and steam cracking?

  Heat and vaporize long chain hydrocarbons
• What catalyst is used in catalytic cracking?

  Hot powdered aluminium oxide
• What happens to long hydrocarbons in catalytic cracking?

  They split into smaller hydrocarbons
• What is mixed with hydrocarbons in steam cracking?

  Steam
• What is produced when long chain alkanes are cracked?

  A shorter alkane and an alkene
• What is the balanced equation for cracking decane?

  C$10$H$22$ → C$8$H$18$ + C$2$H$4$
• What is the significance of alkenes in chemistry?

  They can produce polymers and other chemicals
• What distinguishes alkenes from alkanes?

  Alkenes have a double bond
• Why are alkenes more reactive than alkanes?

  Due to the presence of a double bond
• What happens when bromine water is added to alkenes?

  It decolorizes from orange to colorless
• What is the test for alkenes?

  Decolorization of bromine water
• How do alkenes form polymers?

  By breaking double bonds to bond with others
• What are the key features of alkenes and alkanes?

  • Alkenes:
  • Have a double bond
  • More reactive than alkanes
  • Can form polymers
  • Alkanes:
  • Have only single bonds
  • Saturated compounds
• What are the steps involved in cracking long chain hydrocarbons?

  1. Heat and vaporize long chain hydrocarbons
  2. For catalytic cracking, pass vapor over catalyst
  3. For steam cracking, mix vapor with steam and heat
  4. Split long hydrocarbons into shorter ones