4.8.1 Purity, formulations and chromatography Flashcards
What is a pure substance in chemistry?
A pure substance is a single element or compound, not mixed with any other substance.
How can pure substances be distinguished from mixtures?
Pure elements and compounds melt and boil at specific temperatures.
What does the term ‘pure substance’ mean in everyday language?
It can mean a substance that has had nothing added to it, so it is unadulterated and in its natural state, e.g., pure milk.
What is a formulation?
A formulation is a mixture that has been designed as a useful product.
What are some examples of formulations?
Formulations include fuels, cleaning agents, paints, medicines, alloys, fertilisers, and foods.
What is chromatography used for?
Chromatography can be used to separate mixtures and can give information to help identify substances.
What are the two phases involved in chromatography?
Chromatography involves a stationary phase and a mobile phase.
What is the Rf value in chromatography?
Rf value is the ratio of the distance moved by a compound to the distance moved by the solvent.
How does chromatography help in identifying compounds?
Different compounds have different Rf values in different solvents, which can be used to help identify the compounds.
What will a pure compound produce in chromatography?
A pure compound will produce a single spot in all solvents.
What skills should students develop regarding chromatography?
Students should be able to explain how paper chromatography separates mixtures and interpret chromatograms.
