(20 12? Jieyang) When the balloon is inflated, the air buoyancy is _ _ _ _ (fill in "bigger", "smaller" or "unchanged").

(1) According to the title, when a hot air balloon is inflated, the airbag expands and becomes bigger.

A hot air balloon is in the air,

∴ The volume of air displaced is equal to the volume of the hot air balloon, and the volume of air displaced by the balloon becomes larger;

∫F float =ρair v row g，

A hot air balloon floats from the air.

(2) Heat released by complete combustion of natural gas:

Q amplifier = MQ = 2kg× 4.4x107j/kg = 8.8x107j;

So, the answer is: bigger; 8.8× 107.