I am not understanding the meaning of these lines that is iron does not burn......
Dear Student
You must have heard about the ignition temperature ( The temperature at which anything catches fire).Now iron has strong intermolecular forces of attraction so the surface in contact with air does not reach its ignition temperature due to which it doesn't burn however in case of iron fillings they are small and provide much larger surface area so they reach their ignition temperature easily and burns.
You can also note that in iron rod it has uniform mass so when heat is supplied to it the heat distribute itself throughout the rod so it is difficult to reach its ignition temperature .
Regards
You must have heard about the ignition temperature ( The temperature at which anything catches fire).Now iron has strong intermolecular forces of attraction so the surface in contact with air does not reach its ignition temperature due to which it doesn't burn however in case of iron fillings they are small and provide much larger surface area so they reach their ignition temperature easily and burns.
You can also note that in iron rod it has uniform mass so when heat is supplied to it the heat distribute itself throughout the rod so it is difficult to reach its ignition temperature .
Regards