Key Terms Paper 2
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Define catalyst
Substance which speeds up the ROR by lowering its activation energy without itself being altered or used up
Define alkane
Saturated hydrocarbon containing only hydrogen and carbon atoms
Define alkene
Unsaturated hydrocarbon with a C=C double bond
Define exothermic
When energy is transferred to the surroundings (Energy EXits) More energy released in making bonds than used to break them (MEXO) - net energy decrease
Define endothermic
When energy is absorbed from the surroundings More energy needed to break bonds than released when bonds are made (BENDO) - net energy increase
Define bitumen
The most viscous fraction of crude oil used to surface roads
Define kerosene
A relatively light fraction of crude oil obtained through fractional distillation used as a fuel in aviation
Define saturated
Molecule containing only single bonds e.g. Alkanes
Define unsaturated
Molecule containing at least one double bond e.g. Alkenes
Define allotrope
Different physical forms of the same element in the same physical state but with different structure and properties e.g. Diamond and Graphite and carbon allotropes
Define carbon allotrope
A different form of carbon that has the same chemical composition but different chemical properties
Define activation energy
minimum amount of energy required for a chemical reaction to occur
Define covalent bond
A shared pair of electrons between two non-metal atoms
Define turbidity
Measure of a liquid’s transparency e.g. when the ‘x’ is covered as adding sodium thiosulphate to HCl causes the solution to go cloudy (have a higher turbidity)
Define polymer
A large molecule made up of repeating units called monomers
Define addition polymerisation
Chemical reaction in which monomers with a C=C join to form a single large molecule (a polymer) No byproducts
Define condensation polymerisation
when two monomers with two functional groups (e.g. diols and dicarboxylic acids) react to form a long polymer chain, releasing small molecules like water as byproducts
Define cracking
Process in which a long-chain hydrocarbon is broken down into shorter, more useful hydrocarbons - an alkane and an alkene
Define fractional distillation
Process of separating different lengths of hydrocarbons found in the mixture crude oil
Define catalytic cracking
Method of breaking long-chain alkanes in the presence of a (zeolite) catalyst at 550°C
Define steam cracking
Method of breaking long-chain alkanes without a catalyst at over 800°C
Define zeolite catalyst
The catalyst used to break down long-chain alkanes in catalytic cracking
Define soot
Carbon particulates as a result of incomplete combustion
Define ‘in excess’
There will always be some of that reactant left over as the other reactant is the limiting factor More is present than is needed to react fully with other reactants