Density is mass/volume so if you double the mass you would also double the volume which means density would stay the same. Density is the amount of of matter in a given area and it is constant for the substance regardless of differences in mass or volume.
Becuase you can't change it back to the shiny nail that it was at first So so therefore its a chemical and chemicals can not be changed back into its regular state.
The mass of carbon dioxide that would be produced will be 22 kg
<h3>Combustion of carbon</h3>
The combustion of carbon in air can be represented by the equation:
C + O2 ---> CO2
The mole ratio of C to O2 to CO2 is 1:1:1.
Mole of 6kg of carbon = mass/molar mass
= 6000/12
= 500 moles
Equivalent mole of CO2 produced = 500 moles
Mass of 500 moles CO2 = mole x molar mass
= 500 x 44.01
= 22,005 g or 22 kg approximately
More on combustion reactions can be found here: brainly.com/question/13649083