Analysing and identifying substances Flashcards
What does it mean if something is pure in chemistry?
A pure substance contains only one type of element or compound. For example - water, salt, tin, diamond e.c.t.
What is a mixture?
A mixture is two or more different substances, not chemically joined together. The substances can be elements, compounds, or both.
What is an element?
A substance made of only one type of atom.
What is a compound?
Two or more types of atom joined together.
How do you distinguish between pure substances and mixtures?
Pure substances have a sharp melting point but mixtures melt over a range of temperatures. This difference is most easily seen when the temperature of a liquid is measured as it cools and freezes.
What is a formulation?
A formulation is a mixture which has been designed as a useful product. Every chemical has been added in a carefully measured amount, and has a specific purpose.
Give some examples of formulations.
Paints, fuels, cleaning products, alloys, food, medicines, fertilisers e.c.t.
What is chromatography used for?
Paper chromatography is used to separate mixtures of soluble substances and to provide information on the possible identity of the substances present in the mixture. These are often coloured substances such as food colourings, inks, dyes or plant pigments.
Name the phases of chromatography.
The mobile phase is the solvent that moves through the paper, carrying the substances with it.
The stationary phase is contained on the paper, and does not move through it.
