Mixtures Flashcards
What is a pure substance?
A substance that consists of only one element or compound
What is a mixture?
Contains two or more different substances, NOT chemically joined together
What is filtration used for?
To separate an insoluble solid from a liquid
You want to separate sand from water.
Which method should you use?
Filtration
Describe the setup for filtration.
- Put a funnel in a conical flask
- Put folded filter paper into the funnel
- Pour a beaker containing a mixture through the filter paper / funnel
What is crystallisation?
Producing crystals from a solution by evaporating the solvent
You want to separate copper sulfate from copper sulfate solution.
Which method should you use?
Crystallisation
Describe the three steps to crystalisation.
- put the solution in an evaporating basin
- warm the solution by placing the evaporating basin over a boiling water bath
- stop heating when crystals begin to form around the edge of the basin
When is simple distillation used?
To separate a solvent from a solution
You want to produce pure water from seawater.
Which method should you use?
Simple distillation
Explain how simple distillation works to separate a solvent from a solution.
The dissolve solute has a much higher boiling point than the solvent
Give the three steps to simple distillation of salty water.
- Salty water is heated.
- The water vapour cools in the condenser and drips into a beaker.
- Pure water has condensed into the beaker, and salt stays behind.
What is the name of this process?
Simple distillation
What is condensation?
The change from a gas to a liquid
When is fractional distillation used?
To separate different liquids from a mixture of liquids
You want to separate out the different fractions of crude oil.
Which method should you use?
Fractional distillation
Why does fractional distillation work to separate out different liquids in a mixture?
Because the different liquids have different boiling points
Explain what happens when a liquid is heated in fractional distillation.
- vapours rise through a column which is hot at the bottom, and cooler at the top
- vapours condense when they reach a part of the column that is below the temperature of their boiling point
- each liquid is led away from the column
Which process does this show?
Fractional distillation
When is paper chromatography used?
To separate mixtures of soluble substances
What are the two different phases of paper chromatography?
- stationary phase
- mobile phase (solvent moves through paper)
Why should pencil be used in paper chromatography?
Because pencil is insoluble
Look at this chromatogram.
How many coloured dyes are in brown ink?
Three
What is the name for this process?
Filtration
