1.1 Atoms, elements, compounds and mixtures
5 exam questions worth 11 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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What is the difference between an element and a compound?
Mark scheme
- element: one type of atom (1)
- compound: two or more elements chemically combined (1)
Model answer
An element contains only one type of atom; a compound contains two or more elements chemically combined.
How many atoms of each element are in one molecule of H2SO4?
Mark scheme
- hydrogen 2 (1)
- sulfur 1 (1)
- oxygen 4 (1)
Model answer
Two hydrogen atoms, one sulfur atom and four oxygen atoms.
Which of these is a mixture?
Choose one answer.
Correct Not quite: the answer is Air
Mark scheme
C: air
Model answer
C: air is a mixture of gases that are not chemically combined.
Iron and sulfur are mixed. The mixture is heated and forms iron sulfide.
Give two differences between the mixture and the iron sulfide.
Mark scheme
Any two from:
- mixture not chemically combined, compound chemically combined (1)
- iron can be removed from the mixture with a magnet, not from the compound (1)
- compound has fixed proportions / mixture any proportions (1)
- compound has different properties (1)
Model answer
In the mixture the iron and sulfur are not chemically joined, so the iron can be removed with a magnet. In iron sulfide they are chemically combined in fixed proportions, and the compound has different properties.
Name three physical processes used to separate mixtures.
Mark scheme
Any three from:
- filtration (1)
- crystallisation (1)
- simple distillation (1)
- fractional distillation (1)
- chromatography (1)
Model answer
Filtration, crystallisation and distillation.
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