Question

Iron does not burn on heating but iron fillings burn vigorously when sprinkled in the flame of the burner . Why? Give reason.

Answer 1

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 its ignition temperature and doesn't burn. But iron fillings when sprinkled in flames attain the ignition temperature ( as iron fillings are comparatively smaller particles) and gain a larger surface area for the reaction. Therefore they burn vigorously.