Separating mixtures Flashcards
What does it mean if a substance is pure?
it contains only one type of particle (atom or molecule)
True or false: Only elements are pure substances
False- you can have a pure compound, e.g. pure water (H2O)
What is the difference between the melting point of a pure substance and the melting point of a mixture?
a pure substance changes state at one temperature, a mixture changes state over a range of temperature
What is filtration used for?
To separate insoluble solids from liquids
What equipment do you need for filtration?
funnel and filter paper
During filtration, what is the filtrate?
The liquid which passes through the filter paper
During filtration, what is the residue?
The solid which stays trapped in the filter paper
What is crystallisation used for?
Removing a liquid from a solution
What equipment do you need for crystallisation?
bunsen burner, evaporating basin, tripod
How does crystallisation work?
The water from the solution has a lower boiling point, so evaporates leaving the solid behind
What is simple distillation used for?
To separate a liquid and solid from a solution, or to separate two liquids with different boiling points
How does simple distillation work?
The mixture is heated. The liquid reaches boiling point and evaporates. The gas travels through the condenser where it cools and condenses to be collected.
What equipment do you need for simple distillation?
Bunsen burner, flask, condenser
What is the purpose of the condenser?
To cool the evaporated gas so it condenses and can be collected
What is fractional distillation used for?
To separate a mixture of lots of liquids with different boiling points
What is needed for fractional distillation?
A fractionating column
How does fractional distillation work?
The mixture is heated to form a mixture of gases. The gases rise up the fractionating column and as they do, they cool. Because they have different boiling points, they condense in different places so can be collected.
Which separation technique could be used to separate sand and water?
Filtration
which separation technique could be used to collect water from sea water?
simple distillation
Which separation technique could be used to separate the gases in air?
fractional distillation
Which separation technique could be used to separate copper sulphate crystals from copper sulphate solution?
crystallisation
What is chromatography used for?
separating mixtures of dye
How is chromatography carried out?
A pencil line is drawn on a piece of chromatography paper and a spot of dye is put on the line. The paper is hung with the end in distilled water. As the water is absorbed up the paper, it takes the dye with it, separating out the different colours
Why is the starting line drawn in pencil in chromatography?
because pencil is insoluble so it won’t affect the results
