If it's exposed to extreme heat (like a fire) things can get more exciting, the pressure can rupture the tank, and you get a very impressive explosion.
In the cold the pressure in the tank drops. This is why a propane tank may not supply gas properly if the tank is too cold. If propane gets below about 45C it wont boil any more, and stays as a liquid in the tank.
Propane tanks aren't to be filled to more than 80% of capacity so as to leave room for expansion.
Unless it's been overfilled then it just gets warm. If it has been overfilled it will blow gas out through the safety pressure relief valve, creating a fire or explosion hazard. The normal fill level for one of those tanks is such that you could heat it much more than the sun ever could without it blowing off from that valve, they have enough space in them for a normal full charge of gas to expand safely.
nothing. its under pressure. when warm, it can provide more vapor cfm than cold, but otherwise, absolutely nothing so long as pressure isnt compromised.
