Understanding Chromatography and Separation Techniques

Chromatography
It is a technique based on the different speeds with which each component of a liquid sample can spread through a porous surface, through which the solvent rises by capillary action.
7 Pure Substances: Elements and Compounds
A pure substance that can become simpler substances through transformations is called a compound.
A pure substance that cannot be decomposed into simpler ones is called an element.
A compound is a mixture.
The joining of two or more elements to form a compound is a different process than a mixture.
The constituents of a mixture can be in any proportion and maintain their characteristic properties.
The constituents of a compound are always in the same proportion, and the final substance is a new substance with different properties.
Separation of Components of a Compound
Thermal Decomposition: For example, heating a bit of malachite in a test tube shows a gas cloud of water with lime.
Electrolysis: This is the change produced by the passage of current through the substance, usually molten or dissolved.
Heat and electric current are the main actors in breaking down chemical compounds.

a) Grams per liter of solution: This expresses the grams of solute contained in each liter of solution. Concentration = g. solute / volume of solution in L.
b) Percent by weight: This expresses the grams of solute present in 100 grams of solution. % weight = mass solute / mass solution · 100 (mass of solute dissolution = m + mass of solvent).
c) Percent by volume: This is the volume of solute per 100 volumes of solution.
% volume = volume of solute / volume of solution · 100.
5. Separation of the Components of a Solution
Separation of dissolved solids in liquids: This causes the evaporation of the solvent, and crystallization occurs after the solute.
Separation of liquids dissolved in liquids: To separate components with different boiling points, the solution is distilled in a still; thus, the more volatile component is the first to evaporate.
Separation of a mixture of gases by selective solution: This is used to separate a gas mixture when one of the gases is dissolved in a liquid.
Separation of a gas mixture by distillation: This is chiefly used to separate the components of air.
Liquefaction: The air is compressed to high pressure and is allowed to expand sharply, causing the air to liquefy.
Fractional Distillation: The temperature rises gradually, so that nitrogen evaporates first and then the oxygen.