Pure Substances and Mixtures Flashcards
What is a pure substances?
contains only one substance, with no other substances mixed together
Has fixed melting and boiling point as they consist of only one substance so all molecules will have the same melting and boiling points
E.g. Water has a boiling point of 100°C and a melting point of 0°C
What is a mixture
A combination of two or more substances (elements and/or compounds) that are not chemically joined together
Has a range of melting and boiling points as they consist of different substances that melt or boil at different temperatures
How do you test for purity?
The physical property of boiling/melting point can therefore be used to test if a substance is pure or not.
For example, if a sample of water melts at exactly 0°C and boils at exactly 100°C then the water is pure.
If the melting and boiling points of the water aren’t these exact values then the water must be impure and contain other substances i.e. it must be a mixture.
