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Most IGCSE subjects offer a choice of tiered examinations: Core or Extended papers (in Cambridge International), and Foundation or Higher papers (in Edexcel). This is designed to make IGCSE suitable for students with varying levels of ability. In some subjects, IGCSE can be taken with or without coursework.
GCSE Bitesize was launched in January 1998, covering seven subjects. For each subject, a one- or two-hour long TV programme would be broadcast overnight in the BBC Learning Zone block, and supporting material was available in books and on the BBC website. At the time, only around 9% of UK households had access to the internet at home.
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". [3]
However the exam papers of the GCSE sometimes had a choice of questions, designed for the more able and the less able candidates. When introduced the GCSEs were graded from A to G, with a C being set as roughly equivalent to an O-Level Grade C or a CSE Grade 1 and thus achievable by roughly the top 25% of each cohort.
[30] [31] Generally, the oil is less fluid than crude oil, becoming pourable at temperatures between 24 and 27 °C (75 and 81 °F), while conventional crude oil is pourable at temperatures between −60 and 30 °C (−76 and 86 °F); this property affects shale oil's ability to be transported in existing oil pipelines. [30] [32] [33]
The presence of these chemicals in crude oil is a result of the inclusion of biological material in the oil; these chemicals are released by kerogen during the production of hydrocarbon oils, as these are chemicals highly resistant to degradation and plausible chemical paths have been studied. Abiotic defenders state that biomarkers get into ...
natural water displacing oil downward into the well; expansion of the associated petroleum gas at the top of the reservoir; expansion of the associated gas initially dissolved in the crude oil; gravity drainage resulting from the movement of oil within the reservoir from the upper to the lower parts where well extraction is located.
Naphtha (/ ˈ n æ f θ ə /, recorded as less common or nonstandard [1] in all dictionaries: / ˈ n æ p θ ə /) is a flammable liquid hydrocarbon mixture.Generally, it is a fraction of crude oil, but it can also be produced from natural-gas condensates, petroleum distillates, and the fractional distillation of coal tar and peat.