Simple differences between mixtures and compounds
4 marks · Normal| Substance | Type |
|---|---|
| Oxygen | |
| Water vapour | |
| Carbon dioxide | |
| Helium | |
| Dust particles |
Complete the table by identifying each substance as an element, a compound, or a mixture. (3 marks)
Is air itself an element, a compound, or a mixture? Explain your answer. (1 mark)
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) — · must show Oxygen=element, Water vapour=compound, Carbon dioxide=compound, Helium=element, Dust particles=mixture
(b) Mixture; air contains substances which are not chemically combined and proportions can vary. · must show Air is not chemically combined, Proportions can vary
Common mistakes: Calling water vapour an element; Misidentifying helium; Saying air is a compound
Show mark scheme and worked solution
Marking points
A1 (a) · 1 mark · Correct identification of three or four substances
A2 (a) · 1 mark · Correct identification of all five substances
B1 (b) · 1 mark · States air is a mixture
B2 (b) · 1 mark · Explains that components are not chemically combined and/or that proportions can vary
Worked solution
| Substance | Type |
|---|---|
| Oxygen | Element |
| Water vapour | Compound |
| Carbon dioxide | Compound |
| Helium | Element |
| Dust particles | Mixture |
b) Air is a mixture because it contains substances not chemically combined and the proportions can change.