Seperation Techniques Flashcards
(28 cards)
Give the definition of a pure substance
Has only one element or compound
Give a definition of a mixture
Contains two or more different substances, not chemically joined together
Give a definition of a compound
Contains two or more types of atom joined together
Give an example of a pure element
Oxygen
Give an example of a compound
Carbon dioxide
Give an example of a mixture of elements
Oxygen and helium
Do pure substances have sharp or a range of melting points?
Sharp
Do mixtures melt at a sharp or have a range of melting points?
Range of melting points
What is filtration used to do?
Separate an insoluble solid from a liquid
What does insoluble mean?
Unable to dissolve in a particular solvent eg. Sand in water
Why does filtration work?
The filter paper has tiny holes, or pores in it- large enough to let small molecules and dissolved ions through but not larger particles
What is crystallisation used to produce?
Solid crystals from a solution
Give how you can obtain crystals from crystallisation
-put solution in an evaporation basin
-warm the solution by placing the evaporating basin over a boiling water bath
- stop heating before all the solvent has evaporated
- after cooled, dry the crystals using a warm oven or in air
What is simple distillation used to separate?
A solvent from a solution- producing water from a salt solution
Why does simple distillation work?
The dissolved solute has a much higher boiling point than the solvent- the solvent evaporated from the solution, is cooled and condensed
What’s fractional distillation used to separate?
Different liquids from a mixture of liquids
Why does fractional distillation work?
The different liquids have different boiling points
Give how liquids are collected from fractional distillation
-vapour rises through a column which is hot at the bottom-cold at the top
-vapour condenses when they reach a part of the column that’s below the temp of their boiling point
-the liquid flows out of the column
What is paper chromatography used to separate?
Mixtures of soluble substances- food dye
Give the two phases of chromatography
Stationary phase
Mobile phase
Give what happens during the stationary phase
Very uniform, absorbent paper
Give what happens during the mobile phase
The solvent that moves through the paper, carrying different substances with it
How do you know if a substance is pure on a chromatogram?
Has one spot on the chromatogram
How do you know if a substance is impure on a chromatogram?
Produces two or more spots
