what is an example of blackbody? Aside from a cavity with a small hole, what are the examples of blackbody we observe in our daily lives? For example, if we heat up a chunk of copper and record the emitted radiation, would that spectral distribution be described by the plank's radiation law? is the plank's radiation law only for blackbodies which absorbs all radiation incident on it? or is it for anything that's heated?
If we heat up a chunk of something made of only one type of element, wouldn't the spectral distribution be discrete since atoms absorb and emit photons with only certain energies?
 A: Cosmic Microwave Background is the most perfect black body that have been observed - it has near ideal Planck spectrum at temperature of 2.7 K.
Assuming the theoretical prediction that black holes emit Hawking radiation, it would also be a black body radiation, but it was never observed.
Stars emit almost-black body radiation, but their spectrum contains the spectral lines of the elements present in the star.
No physical object absorbs all wavelengths of ligt completely, so none is a black body and none emits a perfect black body radiation. Still, there are some materials that are pretty close, for example some carbon nanotube arrays can absorb 99.9% of light.
A: The Sun is not a bad approximation to a blackbody radiator.
A blackbody radiator must be capable of absorbing light at all wavelengths and should be in thermal equilibrium. The Sun matches this description reasonably well, the problem is that the depth from which light escapes the Sun is somewhat wavelength-dependent, and because the Sun isn't isothermal and gets hotter with depth, it does not emit a perfect blackbody spectrum.
Other objects may have a spectrum that looks a bit like a blackbody, but with less overall power emitted. Such objects, "grey bodies", have a less-than perfect, but almost wavelength-independent absorption coefficient.
If the absorption coefficient consisted of discrete lines, with gaps, then this could not be a blackbody, since it would not be a perfect absorber at all wavelengths.
In practice, there is always some continuum absorptivity, so providing the object is thick enough, then it can still be a blackbody.
There are lots of duplicate questions on Physics SE which explain what microscopic processes might lead to some continuous absorption in solids or gases.
A: There are a variety of everyday objects which furnish good examples of blackbody radiation, or something very close to it, as follows. 
The electric heat coil in the surface of an electric stove, the filament in a conventional car headlight, the red-hot wires in an electric space heater, and the glowing catalytic grid in a kerosene-fired space heater are all good approximations to a blackbody. 
Note that the emission spectrum of for example a glowing-hot object in equilibrium with its surroundings won't have discrete emission lines in it because the vibrations of the charges in its surface (which produce the radiation it emits) exist in a distribution and generally do not involve ionization and recombination effects.
A notable exception to this is the mercury vapor lamp which produces an emission spectrum with spikes in the UV, green, and blue superimposed on a blackbody background. 
A: Thanks for all the answers. 
But can you answer this one:
If we heat up a chunk of something made of only one type of element, wouldn't the spectral distribution be discrete since atoms absorb and emit photons with only certain energies?
