Question

Iron does not burn on heating but iron filings burn vigorously when sprinkled in the flame of the burner .give reason .

Answer 1

Dear Student,

When an iron block is kept in the flame, the heat is conducted quickly to the area of the block which is not in the flame. To burn the surface of iron in contact with air must be heated to its ignition temperature. Iron has a strong molecular force of attraction. Hence when heated it doesn't reach to its ignition temperature and doesn't burn. But iron fillings when sprinkled in flames attain the ignition temperature ( as iron filings are comparatively smaller particles) and gain larger surface area for the reaction and get surrounded with the flame easily. Therefore they burn vigorously.

Regards