Separation Technqiues

Question 1

Sieving

Answer 1

• Separation based on particle size
• Solid particles pass through perforated barrier

Question 2

Filtration

Answer 2

• Separation based on state of matter
• Undissolved solid particles remain in the filter while liquid/gas passes through
• Filtrate: passes through
• Residue: left behind

Question 3

Evaporation to dryness

Answer 3

• Separation based on boiling point
• Liquid vaporised, leaving solid behind

Question 4

Crystallisation

Answer 4

• Separation based on solubility
• Solution super-saturated, then heated. As solution cools, crystals form and then can be collected

Question 5

Distillation

Answer 5

• Separation based on boiling points
• Liquid heated to form gas. Gas cooled to condense back into liquid

Fractional distillation
- Used when boiling points differ by less than 25 degrees C
- Fractionating column allows temperature gradient to form
- Industrial use example: gasoline

Question 6

Sedimentation

Answer 6

• Separation based on density
• Denser material settles at the bottom

Question 7

Decanting

Answer 7

• Separation based on density
• Liquid poured off sedimented solid

Question 8

Separating funnel

Answer 8

• Immiscible liquids
• Denser liquid run off using separating funnel
• Based on density

Question 9

Centrifugation

Answer 9

• Separation based on density
• Samples spun in a centrifuge, causing extreme sedimentation or filtration