Question

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

Answer 1

Dear Student,...When 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 fillings are comparatively smaller particles) and gain larger surface area for the reaction and get surrounded with the flame easily .Therefore they burn vigorously... Regards.......