Replacements need to be found as crude oil, a fossil fuel, is a finite resource and is non-renewable (it's being used up faster than it is being made). Crude oil is being used up fast
Crude oil:
Made up of hydrocarbons which only contain hydrogen (H) and carbon (C)
It can be seperated with a fractional distillation column:
LPG contains propane and butane gases
Seperation works as follows: intermolecular forces are broken during boiling, these seperate and form gases. Large hydrocarbon chains (eg bitumen) have strong forces of attraction and therefore have high boiling points, so they 'exit' at the bottom
Disadvantages of extracting crude oil:
Damages wildlife (birds' feathers) and can create oil spills. Detergents are used to clean these, which causes further damage to wildlife
The UK is dependant on crude oil from politically unstable countries
Can cause conflict. There is high demand and low production
Cracking:
Turns large alkane molecules (alkanes have only single bonds) into smaller alkane and alkene molecules (alkenes have double and single bonds)
This helps oil manufacturers match demand for products like petrol (smaller molecules)
To crack liquid paraffin, soak it in mineral wool and place at the bottom of a test tube. Clamp this test tube horizontally and place porcelain chips (a catalyst) in the centre. Use a bung with a tube going into an upturned test tube placed in water. Apply heat under the porcelain pieces and the products (gaseous) will collect in the second test tube.
Things to consider when choosing a fuel to use:
Energy value
Availability
Storage
Cost
Toxicity
Pollution
Ease of use
Combustion:
Burning hydrocarbon fuels in air produces carbon dioxide and water: fuel + oxygen -> carbon dioxide + water
Complete combusion: when a fuel burns with enough oxygen, e.g. CH4 + 2O2 -> CO2 + 2H2O
Incomplete combustion: when there is not enough oxygen present, this produces toxic gases and releases less energy than complete combusion. e.g. 2CH4 + 3O2 -> 2CO + 4H2O
Yellow Bunsen flames produce lots of soot (carbon) - incomplete conbustion
The air:
The air contains 78% nitrogen, 21% oxygen, 0.035% carbon dioxide and many other gases such as water vapour
Carbon dioxide composition has increased because of increased population and deforestation causing less photosynthesis
One theory for how the atmosphere evolved is that early volcanoes degassed producing an atmosphere rich in water and carbon dioxide. Water vapour condensed forming oceans. Carbon dioxide was dissolved in these oceans. Due to its lack of reactivity, nitrogen levels increased and photosynthetic organisms developed. Due to photosynthesis, oxygen levels increased
Catalytic converters:
Catalytic converters change carbon monoxide (CO) into carbon dioxide (CO2) with a reaction on the surface of a catalyst: 2CO + 2NO -> N2 + 2CO2
Carbon monoxide is poisonous and oxides of nitrogen cause photochemical smog and acid rain and are formed in the combustion engine due to its high temperatures - nitrogen from the air reacts with oxygen. Sulfur dioxide, another pollutant, kills aquatic life, erodes stonework, corrodes metals and is formed when sulfur impurities in fossil fuels burn
Bromine:
Bromine is used to test for an alkene (alkenes have at least one double bond, see the first section of this module)
When bromine water (orange) is added to an alkene, it decolourises as a colourless dibrimo compound forms
Saturated compounds only have single bonds between carbon atoms. Unsaturated compounds have at least one double bond between carbon atoms, double bonds are shown as follows: C=C
Polymerisation:
Addition polymerisation is when alkene 'monomers' react to create a polymer, under high pressure and with a catalyst. The double bond in the monomer breaks to form the saturated polymer
A displayed formula for a polymer:
Nylon:
Nylon is tough, light and keeps water/light out. Water vapour cannot get through
GORE-TEX® fabric is made from PTFE. It's breathable - water vapour can get through, but not water. It is laminated onto nylon for strength
Problems with disposing of polymers:
Burning produces toxic gases, wastes crude oil
Recycling is difficult - it is hard to sort polymers
Dissolving and biodegradable polymers are being developed
Polymer strength:
plastics that have weak intermolecular forces between polymer molecules have low melting points and can be stretched easily as the polymer molecules can slide over one another
plastics that have strong forces between the polymer molecules (covalent bonds or crosslinking bridges) have high melting points, cannot be stretched and are rigid
Strong covelant bonds hold atoms in polymers together
Polymers with low melting points can be easily stretched, plastics with strong intermolecular forces have high melting points and are therefore rigid
Cooking:
A chemical change takes place if there is a new substance made, or if the process is irreversible, or if an energy change takes place. Cooking is a chemical change due to the first two reasons
Protein molecules in eggs and meat change shape when they are cooked, the shape of the protein molecules change permanently
Potato is easier to digest when cooked as the starch grains swell up and spread out and the cell walls rupture creating a softer texture
Food additives: antioxidants stop foods from reacting with oxygen, food colours improve the colour of the food, flavour enhancers improve the flavour of a food and emulsifiers help oil and water to mix and not seperate
Baking powder decomposes to give carbon dioxide when heated, this is called thermal decomposition. This reaction is shown below: sodium hydrogencarbonate -> sodium carbonate + carbon dioxide + water 2NaHCO3 -> Na2CO3 + CO2 + H2O
If carbon dioxide is present, lime water will turn cloudy
Esters:
Esters are made with an alcohol and a carboxylic acid: alcohol + acid -> ester + water and are used to make perfumes. Esters are made with a condenser which allows for the reaction to go on for longer as it lets gas cool instead of letting it escape
Making an ester: add the acid and alcohol to a flask and add a catalyst - like concentrated sulfuric acid. Fit a condenser to the flask and heat the mixture. Now distill off the remaining mixture to purify it, then transfer it to a funnel with aqueous sodium carbonate, which reacts with remaining acid to neutralise it and remove it into an aqueous layer. This will run off leaving the ester.
Perfumes must have the following properties: they must evaporate easily, so particles can reach the nose, be non toxic and non-irritant, and insoluble in water
In order to evaporate, particles need sufficient kinetic energy to overcome the forces of attraction to other molecules in the liquid
Esters can be used as solvents; a solution is a mixture of a solvent and a solute that doesn't seperate out
Testing of cosmetics on animals is banned in the EU
Water will not dissolve nail varnish colours because the attraction between water molecules is stronger than attraction between water molecules and particles in nail varnish
Paints:
Solvents thin paints, making them easier to spread
A binding medium sticks the pigment in the paint to the surface
Colloids:
Paint is a colloid - the particles are mixed and dispersed with particles of a liquid but are not dissolved
Paint drying:
Emulsion paints are water based and dry when the solvent evaporates
Oil paints dry when the solvent evaporates and the oil is oxidised by the atmospheric oxygen
Phosphorescent pigments:
These glow in the dark because they absorb and store energy, which is released as light over time
Phosphorescent paints are better than radioactive paint because of safety
Thermochromic pigments:
Thermochromic pigments change colour at different temperatures and can be combined with acrylic paints for different colours
Uses include baby spoons and cups to show when they are hot
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