C5 Separating Mixture Flashcards
What is filtration used for ?
To separate an insolvable solid from a liquid.
Why can filtration be used for purification?
Because impurities can be separated out from a reaction mixture using filtration.
How do you use filtration to separate an insoluble solid from a liquid?
Put some filter paper in a funnel and pour your mixture into it.
The liquid part of the mixture runs through the paper, leaving behind a solid residue.
What is crystallisation?
To separate a volume (dissolved solid) from a solution you need to crystallises it
Stages in crystallisation.
Pour solution into an evaporating dish and gently heat.
Some of the solvent (usually water) will evaporate and the solution will get more concentrated.
Once crystals start to form remove the dish from the heat and leave solution to cool.
Filter out the crystals and leave them to dry in a warm place.
What is evaporation?
Heating the solution so some of the solvent evaporates leaving a more concentrated solution or solid.
Why do you not evaporate all of the liquid off in crystallisation?
You could evaporate all the solvent, but you’ll end up with tiny crystals and your substance could decompose.
What is the point of crystallisation?
When you start to see crystals form.
What could you use to dry your crystals?
A drying oven or a desiccator.
What is simple distillation used for?
Separating out a liquid from a solution or to separate liquids that have very different boiling points.
using simple distillation to get pure water from seawater.
Why do you need to connect the bottom end of the condenser to a cold tap using rubber tubing?
Run cold water through the condenser to keep it cool.
Using simple distillation to get pure water from sea water.
What happens when you gradually heat the distillation flask?
The part of the solution that has the lowest boiling point will evaporate.
In this case the water.
Using simple distillation to get pure water from sea water.
What happens to the water vapour that has evaporated, when the distillation flask is gradually heated?
It passes into the condenser where it cools and condenses (turns back into liquid). It then flows into the beaker where it is collected.
Using simple distillation to get pure water from sea water.
What is left in the flask once the water have evaporated?
Salt
What is the problem with using simple distillation?
It only separates things with very different boiling
What method should you use if you have a mixture of liquids with similar boiling points?
Fractional distillation
Complete the sentence
The best technique to separate a mixture will depend on the ………..of the substances in the mixture.
Properties
A mixture is composed of two substance X and Y.
Substance X is a liquid at room temperature. It has a melting point of 5 degree C and a boiling point of 60degree C.
Substance Y is a solid at room temperature. It has a melting point of 745degree C and a boiling point of 1218degree C.
Substance Y dissolves completely in substance X. How can you get substance X on its own?
To get X on its own, you need to distil it from the solution. You can use simple distillation.
A mixture is composed of two substance X and Y.
Substance X is a liquid at room temperature. It has a melting point of 5 degree C and a boiling point of 60degree C.
Substance Y is a solid at room temperature. It has a melting point of 745degree C and a boiling point of 1218degree C.
Substance Y dissolves completely in substance X. How can you get substance Y on its own?
To get Y on its own, you need to get a soluble solid from a solution, so you should use crystallisation.
Describe a method to extract pure copper surface crystals from a copper surface solution (4 marks)
Slowly heat the solution to evaporate off some water (1 mark)
Stop heating once some of the water has evaporated/once copper surface crystals start to form (1 mark)
Allow the solution to cool (1 mark)
Filter the crystals out of the solution and dry them in a warm place/desiccator/drying oven (1 mark)
