(1) When exploring the conditions of sound generation, the music chip that is making sound is hung in a jar, and the sound gradually decreases in the process of gradually pumping out the air in the jar, so it can be inferred that vacuum cannot transmit sound.

(2) When exploring the factors affecting sound intensity, press the steel ruler on the desktop, keep the length of the steel ruler sticking out of the desktop unchanged, stir the steel ruler, listen to the sound and observe the vibration amplitude of the steel ruler, change the amplitude, and make several groups of experiments to draw conclusions. The idea of controlling variables is adopted in the experiment.

Therefore, the answer is: (1) small; Reasoning; Vacuum; (2) amplitude; The length of the steel rule protruding from the desktop; Control variables.