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C12 - Chemical analysis - Coggle Diagram
C12 - Chemical analysis
12.1 Pure substances & mixtures
Definitions
Pure susbtance
A substance made up of just one substance as opposed to multiple
Mixture
When some elements/compounds are mixed together and intermingle but don't react together
Impure substance
A substance made up of two or more pure substances mixed together
Formulation
A mixture that has been designed to produce a useful product
Boiling point
The temperature at which a liquid begins to change into steam/vapour
Melting point
The point at which a substance changes from a solid to a liquid
Surfacant
A substance that decreases the surface tension between two states
Solvent
A substance in which other materials dissolve to form a solution
Binder
A substance used to make other substances/materials stick/mix together
Formulations
Medicinal drugs are formulations. They often only contain 5-10% of the active drug. They can also contain colorants, sweeteners, smooth coatings, fillers and other compounds if taken in tablet form.
Paints are also formulations. They generally contain:
A pigment to provide colour
A binder to help the paint attach itself to an object
A solvent to help the pigment and binder spread well during painting by thinning them out
Pure substances
The melting/boiling points of an element or compound are called its fixed points
You can use melting & boiling points to identify substances because pure substances have characteristic, specific temperatures at which they melt and boil.
Impurities tend to lower the melting point of a substance and raise its boiling point. The purer the compound is, the narrower the melting point range
12.2 Analysing chromatograms
Chromatography is used to separate and identify different amino acids.
In paper chromatography the mobile phase is the solvent chosen, and the stationary phase is the paper.
Paper chromatography can usually tell you if an unknown solution is a single compound or mixture.
Rf value = retention factor
Rf = distance moved by substance / distance moved by solvent
12.3 Testing for gases
Test for hydrogen
Lit splint - squeaky pop
Test for oxygen
Glowing splint relights
Test for carbon dioxide
Limewater turns cloudy
Metal + acid --> salt + hydrogen
Metal carbonate + acid --> water + salt + carbon dioxide
Hydrogen peroxide --> water + oxygen