Purity, formulations, chromatography and identification of gases GapFill

Substances which contain only one kind of element or compound are called  purerefinedpotablesolid. They have a specific  melting pointflammabilitystrengthvolatility, which is often higher than that of  an impurean unrefineda blendeda multiple-compound substance, also known as  a fusionan amalgama mixturea polymer. In a  selectionfractionbrewformulation such as a cleaning product or a fertiliser, every chemical has a specific purpose and is present in its correct  quantitypressurestatetemperature.

Many mixtures containing coloured compounds can be separated using  condensationchromatographyfiltrationpolymerisation. During this process, a  firmsolidconstantstationary phase, such as paper, is placed in a  fluidflexiblechangeablemobile phase, such as water. The substances travel different  patternsspeedsdirectionsdistances up the paper. Dividing the distance travelled by a substance by the distance travelled by the solvent gives the  R_f valuepHpercentageD_s value.

When a gas is produced in a reaction, there are many tests which can be used to find out what the gas is. For example:

• a lit splint gives a squeaky pop with hydrogen
• a glowing splint relights in the presence of  heliumwater vapourmethaneoxygen
• carbon dioxide turns  lime wateracidsthe airmirrors cloudy
•  chlorinebromineheliumnitrogen turns litmus paper white