I'm having an extremely hard time to understand what's going on on the following. Say I have a copper rod and I heat it up with a lighter. I know it will emits photons/EM radiation according to Stefan-Boltzmann's law, namely [itex]P=A \sigma T ^4[/itex] per unit area and that the spectrum is continuous. So far so good. Now say I take copper powder and put it under the lighter flame. Each dust of copper doesn't seem to behave like a black body since the emission spectrum isn't continuous, it's monochromatic! Or at least discrete. Each dust of copper still contains say around 10 ^21 copper atoms, so that I don't understand why the spectrum isn't anything like the one of the copper rod. I'm clearly misunderstanding/missing something, please help me to understand what's going on. Thank you! (very very much!) P.S.:Reformulating my question: What is the difference between heating up black body powder and a black body? Why isn't the spectra of the powder continuous like the one of a black body? I do know that the electrons in copper atoms change of "orbit" and they emit a photon when doing so, but I don't understand why it happens only in the powder form of copper.