Contents
Independent final check
Explain without the key
predict / explain / determine / deduce
Final check
Magnesium is a shiny grey metal, and oxygen is a colourless gas. A pupil holds a strip of magnesium in a Bunsen flame, and a white powder, magnesium oxide, forms. (a) Predict one observation that would show that the change itself gives out energy. (b) Explain why the white powder is evidence that a compound formed, and not a mixture. (c) Two samples of magnesium oxide are analysed. Sample 1 has a mass of 5.0 g and contains 3.0 g of magnesium. Sample 2 has a mass of 8.0 g and contains 4.8 g of magnesium. Determine the mass of oxygen in each sample, and deduce whether the two samples have the same ratio of magnesium to oxygen.
predict: use the information to say what you expect. explain: give reasons and connect them to evidence. determine: find the answer from the information given. deduce: reach a conclusion from the information given.
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Scope and sources
Cambridge IGCSE Chemistry 0620 · 2026–2028 v2 · Original learning materials.
The differences between elements, compounds and mixtures (2.1 Core 1), with iron, sulfur and iron sulfide and with particle diagrams. Atomic structure, formulae and equations, separation methods and energy changes as such are left to their own modules.
Apparatus, amounts and times in the experiment are illustrative. Real practical work follows a teacher-approved safety method.
Official Cambridge syllabus