(2) Calcium oxide reacts with water to release a lot of heat, and the air in the test tube is heated to expand, which makes the balloon expand. The reaction belongs to a combination reaction, and the chemical equation of the reaction is: Cao+H2O ═ Ca (OH) 2;
(3) The metathesis reaction is a reaction in which two compounds exchange components to generate two other compounds. Calcium carbonate reacts with hydrochloric acid to generate calcium chloride, water and carbon dioxide gas, which inflates the balloon. The reaction belongs to metathesis reaction, and the chemical equation of the reaction is: CaCO3+2HCl ═ CaCl2+H2O+CO2 ↑;
(4) Displacement reaction is a reaction in which a simple substance and a compound generate another simple substance and another compound. Zinc is a solid simple substance, which reacts with dilute sulfuric acid to generate hydrogen, making the balloon expand. The reaction belongs to displacement reaction, and the chemical equation of the reaction is: Zn+H2SO4 ═ ZnSO4+H2 ↑.
So the answer is: (1)2H2O2? MnO2？ . ? 2H2O+O2↑； (2)cao+h2o═ca(oh)2； (3)caco3+2hcl═cacl2+h2o+co2↑； (4)Zn+H2SO4═ZnSO4+H2↑.