Air is easily compressable and copper is a good conductor.When u seal the copper tube u compress the air inside and since the container dosen't expand except when heated expands and contracts, the thermal conductivity doesn't change. I hope I was able to answer ur question.
Yes it does b.cos when heated,the gas/air molecules tends to bounce off the wall of the tube and in the process,heats it up.
i mean when it is now heated , does it conduct faster than the ordinary unpressurized open tube?
