Chemical Exploration on Why Magic Balloon Inflates According to the nature of matter, sodium hydroxide can react with carbon dioxide to produce sodium carbonate and water, which makes the gas in the bottle consumed, the pressure reduced and the balloon enlarged.

Sodium hydroxide can react with carbon dioxide to produce sodium carbonate and water, so that the gas in the bottle is consumed, the pressure becomes smaller and the balloon becomes bigger. The chemical equation is: 2 NaOH+CO2 ═ Na2CO3+H2O;

So the answer is: CO2 is absorbed by concentrated NaOH solution, and the air pressure in the conical bottle decreases, and the external air pressure is greater than that in the conical bottle, which makes the balloon expand; 2NaOH+CO2═Na2CO3+H2O.