Active Recall

Section 4 Flashcards

Test yourself on Organic Chemistry with these interactive flashcards. Click each card to reveal the answer.

Edexcel IGCSE Hub › Section 4 › Flashcards

These flashcards cover all key concepts in Section 4. Test yourself using the active recall decks below to solidify your understanding of crude oil, hydrocarbons, functional groups, reactions, and polymerisation.

Introduction & Crude Oil

Intro & Crude Oil: read all 7 questions and answers
  1. Define hydrocarbon.
    A compound containing only carbon and hydrogen atoms.
  2. What is a homologous series?
    A family of compounds with the same general formula, similar chemical properties, and a trend in physical properties, where each member differs by a CH₂ group.
  3. Define functional group.
    An atom or group of atoms that determines the chemical properties of an organic compound.
  4. What is isomerism?
    When two or more compounds have the same molecular formula but different structural formulas.
  5. Describe the process of fractional distillation of crude oil.
    Crude oil is heated and vaporised, then enters a fractionating column which is hot at the bottom and cold at the top. The vapours rise, cool, and condense at their respective boiling points.
  6. State the names and uses of the six main fractions of crude oil from top to bottom.
    Refinery gases (domestic heating/cooking), gasoline (petrol for cars), kerosene (fuel for aircraft), diesel (fuel for some cars/trucks), fuel oil (fuel for ships/power stations), bitumen (road surfacing/roofs).
  7. What are the trends in viscosity, boiling point, and colour as you go down the fractionating column?
    Viscosity increases (becomes thicker), boiling point increases, and colour becomes darker.

Alkanes & Alkenes

Alkanes & Alkenes: read all 13 questions and answers
  1. What are the products of the complete combustion of hydrocarbons?
    Carbon dioxide and water.
  2. What toxic gas can be produced during incomplete combustion, and why is it dangerous?
    Carbon monoxide. It is toxic because it binds to haemoglobin in the blood, reducing its capacity to carry oxygen.
  3. Explain how acid rain is formed from impurities in fuels.
    Sulfur impurities in fuels burn to form sulfur dioxide. High temperatures in car engines cause nitrogen and oxygen in the air to react, forming nitrogen oxides. These gases dissolve in rainwater to form acids.
  4. State the general formula for alkanes.
    \(\text{C}_n\text{H}_{2n+2}\)
  5. Why are alkanes classified as saturated hydrocarbons?
    Because they contain only single covalent bonds between carbon atoms.
  6. State the conditions required for alkanes to react with halogens.
    Ultraviolet (UV) radiation.
  7. What type of reaction occurs when an alkane reacts with a halogen, and what is formed?
    A substitution reaction, forming a halogenoalkane and a hydrogen halide.
  8. State the general formula for alkenes.
    \(\text{C}_n\text{H}_{2n}\)
  9. Why are alkenes classified as unsaturated hydrocarbons?
    Because they contain at least one double covalent bond between carbon atoms.
  10. Describe the chemical test to distinguish between an alkane and an alkene.
    Add bromine water. With an alkene, the orange bromine water is decolourised (turns colourless) without UV light. With an alkane, it remains orange.
  11. What type of reaction occurs when an alkene reacts with bromine?
    An addition reaction, forming a dibromoalkane.
  12. Define cracking.
    The process of breaking down long-chain alkanes into shorter, more useful alkanes and alkenes.
  13. State the standard conditions used for catalytic cracking.
    A temperature of 600 to 700 degrees Celsius and an alumina or silica catalyst.

Alcohols, Acids, Esters & Polymers

Alcohols, Acids, Esters & Polymers: read all 5 questions and answers
  1. State the functional group of alcohols.
    -OH
  2. Explain the two methods used to manufacture ethanol.
    1. Fermentation of glucose using yeast at 30 degrees Celsius in anaerobic conditions. 2. Hydration of ethene with steam at 300 degrees Celsius, 60 to 70 atmospheres pressure, using a phosphoric acid catalyst.
  3. State the functional group of carboxylic acids.
    -COOH
  4. How is an ester formed, and what are its general properties?
    By reacting a carboxylic acid with an alcohol in the presence of an acid catalyst (esterification). Esters have sweet, fruity smells and are highly volatile.
  5. Explain the difference between addition polymerisation and condensation polymerisation.
    Addition polymerisation involves monomer units with double bonds joining together without forming any other products. Condensation polymerisation involves monomers with two functional groups reacting together, releasing a small molecule (like water) for each ester/amide link formed.
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