Category Archives: GCSE C1

Valence electrons and octet rule

  Key Chemistry Concept: Chemical reactions occur by atoms transferring or sharing electrons with each other. However, ONLY the electrons that occupy the outermost shell of atoms are involved in electron transfer or electron sharing between atoms.The electrons that orbit closer to the nucleus are, by definition, not in the outermost shell, and are therefore (usually) unaffected during chemical reactions. Valence number The

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Ethanol

Structure Like alkenes and alkanes, ethanol is another type of organic (carbon-based) compound. Ethanol is a two-carbon length alcohol. All alcohol molecules possess at least one C-OH group, which is known as the functional group (gives the compound its properties). Ethanol has the structural molecular formula, CH3CH2OH However, this often abbreviated to C2H5OH Combustion of ethanol Ethanol combustion (burning) produces carbon

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Polymers from oil

Before we start, an excellent review of this entire topic has been produced by BP Education Polymerisation Alkenes can be used to make polymers such as poly(ethene) and poly(propene). In these reactions, many small molecules (monomers) join together to form very large molecules (polymers). The polymerisation reaction occurs in the presence of a Ziegler-Natta catalyst. The polymerisation process is shown in the images,

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Obtaining useful substances from crude oil (cracking)

Cracking (type of thermal decomposition) Hydrocarbons can be cracked (decomposed) to produce smaller, more useful molecules. There are two types of cracking process that achieve thermal decomposition: catalytic cracking and thermal cracking. Catalytic cracking: the alkane is heated and the vapour is passed over a hot zeolite (aluminosilicate) catalyst. The reaction occurs at around 500ºC. Thermal (steam) cracking: the alkane vapour

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Emulsions

An emulsion is a mixture of two (or more) liquids that are normally immiscible (do not mix together) such that one liquid is dispersed in another  Immiscible liquids Vegetable oils do not dissolve in water. If a mixture of oil and water is shaken, then left to stand, tiny droplets of oil will be seen to float upwards, and eventually

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Vegetable oils: saturated and unsaturated oils (GCSE)

Structure A vegetable oil is a triglyceride extracted from a plant. A fatty acid is a long-chain carboxylic acid that may be saturated (only contains C-C single bonds) or unsaturated (contains C-C single and C=C double bonds). A fatty acid has the general formula of RCOOH, where R is s hydrocarbon that has a length of 16-20 carbon atoms. Three

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