C1.3/4- Separating Mixtures Flashcards
Mixture
- made up of 2/more substances that are not chemically combined
- chemical properties of each substance in the mixture remain unchanged
Element
Made up of one type of atom only
Atom
Smallest part of an element which can be recognised as that element
Chemical compound characteristics
- has a fixed composition
- chemicals in a compound must be separated by a chemical reaction
- they have chemical bonds between the atoms of the different elements in a compound
Fixed composition meaning
Ratio of elements present is always the same in any particular compound
I.e H20
Mixture characteristics
- has no fixed composition
- different elements in a mixture can be separated more easily
- there are no chemical bonds between the atoms of different substances in the mixture
Separating mixtures method
- by physical means
- using the differences in properties of each substances
- relying on properties like boiling points or magnetism
Techniques to separate mixtures
- filtration
- crystallisation
- distillation
- chromatography
Filtration
-separates substances that are insoluble in a particular solvent from solute
Example of filtration method
1- fill up beaker with 50ml of water
2-pour 4-5 spatula scoops of rock salt and stir
3- outline a conical flask with filter paper and pour in solution
4-filtration will take place here, removing any insoluble matter on the paper and leaving the filtrate to pass through
Filtration of rock salt: equipment
- beaker
- sodium chloride
- spatula
- conical flask
- filter paper
- rock salt
Crystallisation
-usually used to separate salt and water solutions
-Done by:
Heating up the solution in an evaporating dish over a water bath
Then the heat should be removed allowing the remain water to evaporated at room temperature
Distillation
- this process allow us to collect the solvent instead of letting it evaporate into the air
- allows us to purify water
- eg allows us to turn seawater into usable water
Simple distillation
1- solution is heated to evaporate the solvent
2- vapour given off then enters the condenser so that it can be turned into a liquid
-it is the collected in a receiving vessel
-any remaining matter will be left in the heating flask
Condenser
- outer glass tube
- has water flowing through it that acts as a ‘cooling jacket’ around the inner glass tube from the flask
Solvent
The liquid in which the solute dissolved
-usually water
Solute
The substance that dissolved into a liquid to form a solution
Solutions
Mixture formed when a solute has dissolved in a solvent
Soluble
Describes a substance that is able to dissolve
Insoluble
Describes a substance that will not dissolve
Fractional distillation
-separates mixtures of miscible liquids and liquids that have different boiling points
Miscible
-Describes liquids that dissolve into each other or mix completely
-they will not form separate layers seen in immiscible mixtures
I.e oil+water
Miscible liquid properties
-have different boiling points
Fractional distillation method
- collect the liquid with the lowest boiling point first as it will evaporate first
- adding a fractionating column means that both vapours will pass through the beads
- but the substance with the higher boiling point will condense and fall back down
- while the liquid with the lower boiling point will pass through and enter the condenser
Fractionating column
- a tall glass column filled with glass beads
- fitted right on top of the heating flask
- the higher up you go the lower the temperatures
Fractional distillation use
- used to separate ethanol from fermented mixture in the alholic spirits industry
- then the ethanol is used as biofuel
Paper chromatography
- used to separate substances from mixtures in a solution
- analyses colours in a solution (ink)
- works as some compounds in a mixture will dissolve better than others in the solvent selected
Equipment for paper chromatography
- 1 pen
- 1 food colouring
- solution
- pencil
- chromatography paper
- capillary tube
- solvent
Method for paper chromatography
1-draw a pencil line near the bottom of the sheet of paper
2-use a capillary tube to dab a spot of ink
3-place the paper standing upright in the beaker filled with the solvent
4-the paper will soak up the solvent and run through the spot of ink
Why does paper chromatography work
- the higher up the substance is on the paper, the more soluble it is
- it separates the mixture to be identified
