Hydrocarbons

• What do the physical properties of crude oil fractions depend on?

  Size of the hydrocarbons in that fraction
• What are homologous series in chemistry?

  • A family of molecules
  • Same general formula
  • Share similar chemical properties
• What is a characteristic of homologous series?

  They have the same general formula
• How do molecular formulas of neighboring compounds in homologous series differ?

  By a $CH_2$ unit
• How do physical properties of compounds in homologous series vary?

  They vary between different molecules
• What happens to the boiling point as the size of the molecule increases?

  The boiling point increases with larger molecules
• What is the molecular formula of methane?

  $CH_4$
• What is the molecular formula of ethane?

  $C_2H_6$
• What is the molecular formula of propane?

  $C_3H_8$
• What is the molecular formula of butane?

  $C_4H_{10}$
• What is the molecular formula of pentane?

  $C_5H_{12}$
• How does the size of a hydrocarbon affect its properties?

  It determines its physical properties
• Why do larger hydrocarbons have higher boiling points?

  Stronger intermolecular forces hold them together
• What is the relationship between molecular size and intermolecular forces?

  Larger molecules have stronger intermolecular forces
• If a molecule is larger, what can be inferred about its boiling point?

  It likely has a higher boiling point
• What factors determine the properties of hydrocarbons?

  • Size of the hydrocarbons
  • Intermolecular forces
  • Molecular structure
• What is the boiling point of methane?

  -161 °C
• What is the boiling point of ethane?

  -88 °C
• What is the boiling point of propane?

  -42 °C
• What is the boiling point of butane?

  -0.5 °C
• What is the boiling point of pentane?

  36 °C
• Why do larger hydrocarbons have higher boiling points than smaller ones?

  Due to stronger intermolecular forces
• What are the implications of molecular size on hydrocarbon properties?

  • Larger size leads to higher boiling points
  • Stronger intermolecular forces in larger molecules
  • Similar properties among molecules in a fraction
• What do forces do to molecules at certain points along their length?

  They attract it to another molecule
• What type of intermolecular force do small molecules have?

  Weak intermolecular force
• What type of intermolecular force do big molecules have?

  Strong intermolecular force
• What happens when gas molecules mix with oxygen in the air?

  They produce a gas mixture that burns
• What do longer hydrocarbons usually exist as at room temperature?

  Liquids
• Why do longer hydrocarbons have higher boiling points?

  They are harder to ignite
• How does intermolecular force strength affect liquid flow?

  Stronger forces make liquids flow harder
• What are the characteristics of fuels in combustion reactions?

  1. Hydrocarbons make great fuels.
  2. They release a lot of energy when burned.
  3. Complete combustion produces carbon dioxide and water.
  4. Incomplete combustion occurs with limited oxygen supply.
• What is the equation for complete combustion of hydrocarbons?

  Hydrocarbon + oxygen → carbon dioxide + water
• What occurs during incomplete combustion of hydrocarbons?

  Produces carbon monoxide and soot
• What causes the difference in properties between hydrocarbons?

  Intermolecular forces between carbon chains
• What is the relationship between hydrocarbon chain length and viscosity?

  Longer chains have higher viscosity
• How does the viscosity of a substance relate to its flow characteristics?

  Higher viscosity means slower flow
• What happens to the properties of hydrocarbons as their chain length increases?

  They become thicker and harder to ignite
• What is the significance of intermolecular forces in hydrocarbons?

  They determine boiling points and viscosity