Question

Why dirty snow melts faster than the clean snow?

Answer 1

Dirty snow melts faster than clean snow because the dirt in dirty snow is dark in color, absorbing solar radiation. This causes dirty snow to melt faster than clean snow, which reflects most solar radiation back into the atmosphere rather than absorbing it.! I hope u got your answer.

Answer 2

Presence of impurities in a substance decrease the melting point.  The intermolecular attraction force between the molecules of snow (ice) become less because of mixing of impurities.  The dirt molecules attract some molecules of snow, so the adhesive force becomes a little less.