In chemistry class, Mr  Zhang demonstrated two simultaneous teaching experiments: one is that O2 is produced slowly after KCIO3 heating; the other is that KCIO3 is heated and a small amount of MnO2 is quickly sprinkled into it, and a large amount of O2 is produced immediately
Teacher Zhang pointed out that MnO2 is the reason for the rapid production of O2
Put the alarm clock in the glass cover to ring the bell, you can hear the bell; then empty the air in the glass cover, and then make the alarm clock ring, the bell will not be heard. Thus it can be seen that air is the medium of sound transmission.