BRAINCAKEAlkanes
Revision notes for Alkanes in AQA Chemistry (7404). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.
- General FormulaAlkanes are saturated hydrocarbons.
- Straight ChainsIn a straight-chain (unbranched) alkane, each carbon atom is joined to no more than two other carbon atoms.
- Branched ChainsIn a branched-chain alkane, at least one carbon atom is joined to three or four other carbon atoms, so side chains come off the main chain.
- Cyclic AlkanesCycloalkanes are saturated hydrocarbons in which the carbon atoms are joined in a ring.
- Naming AlkanesTo name an alkane, first find the longest continuous carbon chain.
- Structural IsomersStructural isomers of alkanes have the same molecular formula but different arrangements of the carbon chain.
- Physical PropertiesAlkanes are non-polar molecules because carbon and hydrogen have very similar electronegativities.
- Fractional Distillation of Crude OilCrude oil is a mixture consisting mainly of alkane hydrocarbons, with different chain lengths.
- FrackingFracking (hydraulic fracturing) is a method of extracting natural gas and oil trapped in shale rock deep underground.
- Thermal CrackingCracking is the breaking of C-C bonds in long-chain alkanes to form shorter, more useful molecules.
- catalytic CrackingCatalytic cracking breaks long-chain alkanes using a zeolite catalyst, a high temperature of about 450 °C and a slight pressure.
- CombustionAlkanes are used as fuels because they burn in oxygen, releasing a large amount of energy.
- Polluting the AtmosphereBurning fossil fuels in engines and power stations releases several pollutants into the atmosphere.
- Flue Gas DesulfurisationFlue gas desulfurisation removes sulfur dioxide from the waste gases (flue gases) of power stations before they are released, to reduce acid rain.
- Catalytic ConvertersCatalytic converters are fitted to car exhausts to remove carbon monoxide, nitrogen oxides and unburnt hydrocarbons.
- Greenhouse EffectThe Sun emits radiation, mainly visible and ultraviolet, which passes through the atmosphere and warms the Earth's surface.
- Carbon Neutral ActivitiesA carbon neutral activity has no overall annual carbon emissions to the atmosphere.
- Free-Radical SubstitutionAlkanes react with halogens such as chlorine in the presence of UV light.
- Further SubstitutionFree-radical substitution does not stop after one hydrogen has been replaced.
- Ozone LayerThe ozone layer is a region of the stratosphere containing ozone, O3.
On the specification
- 3.3.2.1 Fractional distillation of crude oil
- 3.3.2.2 Modification of alkanes by cracking
- 3.3.2.3 Combustion of alkanes
- 3.3.2.4 Chlorination of alkanes