I'm doing some physics questions from an old test but struggle with a few questions. Problem: An air balloon with the volume 5000m^3 should be able to lift a total mass of 1000kg, including the cargo and everything. The surrounding air keeps a constant temperature of 12C and has the density of 1.2kg/m^3. How hot does the air in the balloon need to be in order to lift this? I've tried using some different gas law formulas, in particular pV = nRT but to no success, always seems like I'm missing some information. All help and thoughts is much appreciated!