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They are sold as revision material for GCSE and A-level exams particularly as literary guides to introduce students to sophisticated analysis and perspectives of the specific title. The guides for A-level are sold under the name York Notes AS/A2, the GCSE guides under the name York Notes for GCSE with each guide attributed to its relevant author.
A mnemonic is a memory aid used to improve long-term memory and make the process of consolidation easier. Many chemistry aspects, rules, names of compounds, sequences of elements, their reactivity, etc., can be easily and efficiently memorized with the help of mnemonics.
Until 2014, the Standard Grade section of the site had 12 subjects: Biology, History, Chemistry, Computing Studies, Maths, English, Modern Studies (a course exclusive to Scotland), French, Physical Education, Geography, and Physics. [9] The site was updated in 2014 to replace the Standard Grade section with National 4 and National 5 sections.
A chemical equation is the symbolic representation of a chemical reaction in the form of symbols and chemical formulas.The reactant entities are given on the left-hand side and the product entities are on the right-hand side with a plus sign between the entities in both the reactants and the products, and an arrow that points towards the products to show the direction of the reaction. [1]
CH 3 CH 2 OH . Parentheses are used to indicate multiple identical groups, indicating attachment to the nearest non-hydrogen atom on the left when appearing within a formula, or to the atom on the right when appearing at the start of a formula: (CH 3) 2 CHOH or CH(CH 3) 2 OH . In all cases, all atoms are shown, including hydrogen atoms.
History [ edit ] In August 2018, Ofqual announced that it had intervened to adjust the GCSE Science grade boundaries for students who had taken the "higher tier" paper in its new double award science exams and performed poorly, due to an excessive number of students in danger of receiving a grade of "U" or "unclassified".
A molecular formula enumerates the number of atoms to reflect those in the molecule, so that the molecular formula for glucose is C 6 H 12 O 6 rather than the glucose empirical formula, which is CH 2 O. Except for the very simple substances, molecular chemical formulas generally lack needed structural information, and might even be ambiguous in ...
An example of the difference is the empirical formula for glucose, which is CH 2 O (ratio 1:2:1), while its molecular formula is C 6 H 12 O 6 (number of atoms 6:12:6). For water, both formulae are H 2 O. A molecular formula provides more information about a molecule than its empirical formula, but is more difficult to establish.