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Pure
,→Key Stage 4
: '''Purity''' is important for ensuring that when [[Chemical Reaction|reaction]]s take place there are no unwanted [[product]]s caused by the '''impurities'''.
: '''Impurities''' can change the [[property|properties]] of a [[substance]] such as its [[Melting Point|melting point]], [[Electrical Conductivity|electrical conductivity]] or [[Strength (Property)|strength]]. This means '''purity''' is essential when using [[substance]]s for certain [[application]]s where those [[property|properties]] important.
'''Purity''' may refer to:
*A '''pure''' [[element]] - A [[substance]] containing only one type of [[atom]].
*A '''pure''' [[compound]] - A [[substance]] containing only one [[chemical]] [[compound]].
===Detecting Purity===
: The '''purity''' of a sample can be checked by looking at its [[property|properties]] such as the [[Melting Point|melting point]] and [[Boiling Point|boiling point]]. If these are spread over a range of [[temperature]]s or different from the known values for the [[pure]] [[substance]] then the sample is not [[pure]].
: To test if a sample of [[Water]] is [[pure]] it can be [[melting|melted]] from [[Ice]] and [[boiling|boiled]] from [[liquid]] [[Water]]. If the [[Melting Point|melting point]] is exactly 0°C and the [[Boiling Point|boiling point]] is exactly 100°C, then the [[Water]] is [[pure]].