More Information on Separating Mixtures

3 Thoughts:
1) There is more apparatus use in fractional distillation than in distillation. The extra apparatus use in fractional distillation is called fractionating column. The substance which has the lowest boiling point will be found right at the top of the fractionating column. In addition, the substance which is the heaviest in weight will be at the bottom of the fractionating column.
2) The mixture being separated in the fractional distillation has a wide range of temperatures and there is a great difference between the temperatures. Example, there are three substances in the mixture in which their temperatures may be 30 degree Celsius, 70 degree Celsius and 120 degree Celsius. Fractional distillation is usually used to separate more than two substances from a mixture while distillation can at most separate a mixture which contains two substances.
3) By using the method called paper chromatography, a solvent (e.g. alcohol) must be used. When using the chromatography paper (long strip), a pencil mark should be drawn at around 2 or 3cm above the bottom of the strip. Ink must not be used on the strip as when it comes into contact with the solvent, the substances in it will also be separated. The pencil mark should also be above the solvent. If the pencil mark is in the solvent, the mixture will mix with the solvent and becomes another mixture. Thus, the separation of the previous mixture will not be the same and accurate. Lastly, a cock is used to cover the boiling tube so that the alcohol will not be evaporated.

2 Questions:
1) When we use the paper chromatography method, how do we know that all the substances in the mixture have been separated?
2) Why is there fractional distillation and distillation? Can the mixture which only contains two substances be separated using the fractional distillation method such that all the mixtures on Earth can be separated by the fractional distillation method and the distillation method need not be used anymore?

1 Useful application:
1) Since we know the method in using the distillation method to separate mixture, we are able to separate the substances in the mixture by ourselves if we want to use the substance which is found in the mixture. The substances in the mixture are also useful to us.