Methods of Separating and Purifying Substances - Paper 1 Flashcards
How can pure substances be differentiated from mixtures based on melting point data?
Pure substances have a sharp melting point, while mixtures melt over a range of temperatures.
Which types of mixtures can be separated by simple distillation?
Simple distillation can separate a solvent from a solution.
Which types of mixtures can be separated by fractional distillation?
Fractional distillation can separate different liquids from a mixture of liquids, based on boiling point.
Which types of mixtures can be separated by filtration?
Filtration can separate an insoluble solid from a liquid.
Which types of mixtures can be separated by crystallisation?
Crystallisation can produce solid crystals from a solution.
Which types of mixtures can be separated by paper chromatography?
Paper chromatography can separate mixtures of soluble substances.
Define paper chromatography
Paper chromatography is the separation of mixtures of soluble substances by running a solvent (mobile phase) through the mixture on the paper (the paper contains the stationary phase), which causes the substances to move at different rates over the paper.
Define Rf value
The Rf value of a spot is equivalent to the distance travelled by the substance divided by the distance travelled by the solvent.
Explain the steps involved in treating waste or groundwater to make it potable.
- Screening
- Coarse filtration
- Sedimentation
- Fine filtration
- Chlorination
Explain sedimentation in making water potable.
In sedimentation, aluminium sulfate is added to clump small insoluble particles together, which then settle to the bottom in a sedimentation tank.
Explain filtration in making water potable.
A coarse filter bed made from clean sand and gravel removes large insoluble grit particles.
A fine filter bed removes very small insoluble particles.
Explain chlorination in making water potable.
Chlorine gas is added to kill microorganisms.
How can seawater be made potable?
Through simple distillation.
Why must distilled water be used in analysis?
Distilled water does not contain any dissolved ions that might interfere with a chemical analysis.
