C1 OCR

C1 OCR

1. Making Crude Oil Useful

   • Crude oil is a mixture of many hydrocarbons
   • Cracking helps an oil refinery match its supply of useful products, such as petrol with the demand for them
     • Cracking converts large alkane molecules into smaller alkane and alkene molecules
   • Fossil fuels are finite resources because they are no longer being made or are being made extremely slowly
     • They are non renewable resources as they are being used up faster than they are being formed
   • Crude oil can be separated by fractional distillation. It is heated near the bottom of a fractionating column. Fractions with low boiling points exit at the top. Fractions with high boiling points exit at the bottom
     • There is a temperature gradient between the top and bottom of the column
   • Hydrocarbons with bigger molecules have stronger intermolecular forces between their molecules, and therefore have higher boiling points than hydrocarbons with smaller molecules

2. Fuels and Clean Air

   • Photosynthesis, respiration and combustion are processes in the carbon cycle
   • The original atmosphere came from the degassing of early volcanoes which were rich in water and carbon dioxide. the water condensed to form oceans. Photosynthetic organisms helped to increase the levels of oxygen through photosynthesis
   • The present day atmosphere contains 21% oxygen, 78% nitrogen and 0.035% carbon dioxide
   • Key factors that need to be considered when choosing a fuel are energy value, availability, storage, toxicity, pollution caused and ease of use
   • If hydrocarbons burn in a plentiful supply of air, carbon dioxide and water are made. In an experiment, carbon dioxide can be tested for with limewater; if there is carbon dioxide present, the limewater turns milky

3. Polymers

   • A hydrocarbon is a compound of carbon atoms and hydrogen atoms only
   • Alkanes are hydrocarbons which contain single covalent bonds only.
   • Alkenes are hydrocarbons which contain a double covalent bond between carbon atoms
   • plastics that have weak intermolecular forces between the polymer molecules can be stretched as the polymer molecules can slide over one another
     • Rigid plastics have cross-linking bridges
     • Addition polymers are made when alkane monomer molecules react together under high pressure and with a catalyst
   • Nylon and GORE-TEX are polymers with suitable properties for different uses.
     • Nylon is tough, lightweight and keeps water and UV light out
       • GORE-TEX has all of these properties but allows water vapour to pass out so that sweat does not condense

4. Food and smells

   • Protein molecules in eggs and meat denature when they are cooked
     • The change shape of a protein molecule is permanent
   • Emulsifiers are molecules with a water loving (hydrophilc) part and an oil loving (hydrophobic) part.
     • The hydrophilic end bonds to water molecules
     • the hydrophobic end bonds to oil molecules keeping the oil and water from sepatating
   • Perfumes need to be able to evaporate so that they can easily reach the nose
     • To evaporate, particles need sufficient kinetic energy to overcome their attraction to other molecules in the liquid

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