Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
14 Cards in this Set
- Front
- Back
|
Meaning of Mixture |
Mixture is made up of two or more substance that are not chemically combined |
|
|
Meaning of pure substance |
Made up of single element or compound. It is not mixed with any other substance |
|
|
Effects of impurities on melting point? |
Lower the melting point of a solid. The greater the amount of impurities, the lower the melting point. Causes melting point to take over a range of temperatures. e.g. benzoic acid may melt over a temperature range of 118-121*C |
|
|
Method of separation |
Filtration Evaporation to dryness crystallisation using a suitable solvent simple distillation Fractional distillation |
|
|
When to use Filtration |
Separating an insoluble solid from a liquid separate insoluble solid particles from a liquid the solid left on the filtrate paper is called residue The liquid that passed through the filtrate paper is called the filtrate |
|
|
when to use Evaporation to dryness |
separating a soluble solid from a liquid obtain a soluble solid from a solution by heating it until the water has boiled off |
|
|
when to use Crystallisation |
separating a soluble solid from a liquid solid decompose upon strong heating Obtain a pure solid sample from its solution When heating, it does not heat till it boils E.g. Sugar decompose to water and carbon when heated strongly. |
|
|
When to use a suitable solvent method |
solvent meaning: the remains of a solution after separation is a solvent Separating a soluble solid from an insoluble solid |
|
|
when to use Simple distillation |
Used to separate a pure solvent from a solution 2 things to remember in the diagram: Thermometer and condenser |
|
|
Procedure to note: |
Thermometer: The bulb of the thermometer should be placed beside the side arm of the distillation flask. it should not be dipped into the solution. Reason ensures that the thermometer measures the boiling of the substance that is being distilled Condenser: 1)The condenser should be sloped downwards. The condenser consist of 2 tubes: an inner tube and outer water jacket 2)Cold running water is allowed to enter the water jacket from the bottom of the condenser and leaves at the top. Reason 1)Ensure that the pure solvent formed runs downwards into the receiver (conical flask) 2) if water enters from the top of the condenser, it will exit the condenser before the water jack can be completely filled. Thus it must enter from the bottom to keep the jacket always completely filled. Also a more efficient way of cooling. |
|
|
when to use fractional distillation |
Used to separate a mixture of miscible liquid. 2 things to remember in the diagram: glass beads and fractionating column |
|
|
Fractionating column and glass beads |
When the 2 liquid vapour rise up, the one with higher boiling point condense along the fractionating column and fall back into the round-bottomed flask. |
|
|
When to use Choromatography |
Separating two or more components that dissolve in the same solvent used to test from banned substance present in food colouring |
|
|
How to identify a banned substance present in food colouring? |
1.Paper chromatography is used to separate the dyes in the sample. 2. Each dye is identified by comparing its position in the chromatogram with that of a known dye on the same chromatogram 3. Chemist can then check against a database of banned dye to see if the dyes are permitted for use in food |
