Separation techniques

Question 1

Describe the melting and boiling points of a mixture

Answer 1

Mixtures melt or boil over a range of temperatures.
For example, salt in water (salt solution) boils between 90 and 110°C.

Question 2

Describe the melting and boiling points of pure substances

Answer 2

Pure substances melt or boil at sharp temperatures.
E.g. Water boils at 100°C.

Question 3

What are the 2 phases in chromatography?

Answer 3

Mobile and stationary phase

Question 4

Define chromatography

Answer 4

A process that separates a mixture into its different components

Question 5

Define a pure substance

Answer 5

One single element of compound

Question 6

What process is used to treat sea water?

Answer 6

Distillation

Question 7

How is water treated?

Answer 7

Sedimentation
Filtration
Chlorination

Question 8

What is distilled water

Answer 8

contains no other ions or molecules that could interfere with chemical tests.

Question 9

What are formulations?

Answer 9

Mixtures of chemical components that are designed to create useful products

Question 10

Give an example of a formulation

Answer 10

Fuels, cleaning agents, metal alloys

Question 11

What impact do impurities have on boiling point of a substance

Answer 11

Increase the boiling point and widen the range of temperatures the substance will boil at

Question 12

What impact do impurities have on melting point of a substance

Answer 12

They lower the melting point and widen the range of temperatures a substance will melt at

Question 13

Which phase the solvent represent in paper chromatography?

Answer 13

Mobile phase

Question 14

How does paper chromatography work

Answer 14

Place a drop of the solution to be separated near the bottom of a piece of chromatography paper. Dip the very bottom of the paper into a suitable solvent. The solvent (liquid) moves up the paper and carries the solutes (solids) in the solution with it.
Different solutes (solids) move at different speeds, so they separate on the paper.

Question 15

How does crystallisation work

Answer 15

Heat the mixture so that the solvent evaporates.
Eventually, crystals of the solute (dissolved solids) will form.
We can collect the solvent (liquid) by condensing it as it evaporates.

Question 16

How does filtration work

Answer 16

Done by pouring the mixture through filter paper:
The insoluble solid is trapped.
The liquid runs through the paper and is collected below.

Question 17

How does fractional distillation work

Answer 17

The mixture is slowly heated until the liquid with the lowest boiling point boils and then condenses.
Then we increase temperature slowly to collect (boil then condense) the other fractions.