Analysis of the test questions: a, the balloon explosion is caused by the expansion of gas in the tire, and no new substances are generated, which belongs to physical changes; B, the essence of disinfection is to denature the protein, make the pathogenic protein of pathogenic microorganisms lose its function, change the spatial structure of protein, or degrade the protein, so that the combination of molecules and atoms conforms to the definition of chemical change. So it is a chemical change; C, platinum processing into jewelry is only a change in shape, and no new substances are produced, which is a physical change; D, separation of liquid air to make oxygen, there is oxygen in the air, so the option is wrong.