Which description correctly describes air?
A pure compound
A mixture of elements and compounds
A pure element
What does a mixture consist of?
One type of atom only
Two or more elements that are chemically joined
Two or more pure substances that are not chemically joined
What name is given to a mixture that always contains a fixed proportion of components?
An emulsion
A formulation
A fixture
If a substance has a sharp melting point, what does this tell you?
It is a mixture
It is impure
It is pure
What is the solvent called in paper chromatography?
The mobile phase
The stationary phase
The liquid state
How many spots will a pure substance produce during chromatography?
1
2
3
What is the Rf value of a substance that travels 5 cm up the paper, compared with the solvent that travels 10 cm?
50
0.5
Which separation technique separates an insoluble substance from a liquid?
Filtration
Chromatography
Distillation
During fractional distillation in the lab, which fraction is collected first?
The fraction which has the highest boiling point
The fraction which has the lowest boiling point
The fraction which has a medium boiling point
Which is the best way to form large crystals during crystallisation?
Heat the solution and evaporate all the solvent
Evaporate some of the solvent and then chill the remaining solution
Evaporate some of the solvent, and then allow the remainder to evaporate slowly