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Chemistry Paper 1: C1 (Fuels and clean air (Key factors that need to be…
Chemistry Paper 1: C1
Fuels and clean air
Key factors that need to be considered when choosing a fuel are energy value, availability, storage, toxicity, pollution caused and the ease of use
Photosynthesis, respiration and combustion are processes in the carbon cycle
The present day atmosphere contains 21% oxygen, 78% nitrogen and 0.035% carbon dioxide
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 levels of oxygen through photosynthesis.
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 the limewater test, if carbon dioxide is present it turns the limewater milky
Making crude oil useful
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 and fractions with high boiling points exit at the bottom this means there is a temperature gradient between the bottom and the top of the column
Hydrocarbons with bigger molecules have stronger inter molecular forces between their molecules and so have higher boiling points than hydrocarbons with smaller 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
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
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Polymers
Addition polymers are made when alkene monomer molecules react together under high pressure and with a catalyst
Plastics that have weak inter molecular forces between the polymer molecules can easily be stretched as the polymer molecules can slide over one another; Rigid polymers have cross-linking bridges
Alkanes are hydrocarbons which contain single covalent bonds only; Alkenes are hydrocarbons which contain a double covalent bond between the carbon atoms
Nylon and GORE-TEX are polymers with suitable properties for particular uses; Nylon is tough, lightweight and keeps water and UV light out; GORE-TEX has all these properties but allows water vapour to pass out so that sweat does not condense
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Food, smells and paints
Emulsifiers are molecules with a water loving (hydrophilic) part and an oil loving (hydrophobic) part; The hydrophilic end bonds to water molecules and the hydrophobic end bonds to oil molecules, keeping the oil and water from seperating
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
Protein molecules in eggs and meat denature when they are cooked; The change of shape of the protein molecule is permanent
Paints are colloids because the particles are mixed and dispersed throughout a liquid but are not dissolved in it; thermochromic pigments change colour with heat and are used, for example in babies toys that are immersed in water to show whether the water is too hot; Phosphorescent pigments glow in the dark and are much safer for use in products than the alternate radioactive substances