2006-07-19 02:59:01 · 4 answers · asked by prabhjot k 1 in Science & Mathematics ➔ Chemistry
Pure substances have definite melting point (m.p.) . When some impurities are mixed to a pure substance the mp does not remain same.M P of pure substance is always higher than the impure substance. Normally mp and freezing points are the same for many substances though exceptions are there.
2006-07-19 03:16:24 · answer #1 · answered by papa 2 · 0⤊ 0⤋
Adding to the previous answers...
The crystal lattice of a pure substance should be quite uniform so it breaks up at a certain temperature (or very small range of temperatures).
Having impurities introduces irregualrities in the lattice which make it break easier (needs less energy to disrupt the interactions and thus lowers melting point) and different parts of it can melt at slightly different temperatures depending on their content in impurities and lattice deformation (wider range of melting temperature)
2006-07-19 11:36:42 · answer #2 · answered by bellerophon 6 · 0⤊ 0⤋
Certain substances in their purest form have and exact melting point. If other substances contaminate this substance, the melting point won't be the same.
2006-07-19 10:02:54 · answer #3 · answered by Anonymous · 0⤊ 0⤋
well you can compare it to the literature value for one, secondly the purer the compound the smaller the melting range is
2006-07-19 13:50:33 · answer #4 · answered by shiara_blade 6 · 0⤊ 0⤋