Explain the observation of Alenxander vaon Humboldt.

According to Alexander von Humboldt:

Explain the following observations

During the reaction of some metals with dilute hydrochloric acid, following observations were made. Silver metal does not show any change. Explain these observations giving suitable reasons.

During the reaction of some metals with dilute hydrochloric acid, following observations were made. The reaction of sodium metal is found to be highly explosive. Explain these observations giving suitable reasons.

During the reaction of some metals with dilute hydrochloric acid, following observations were made. Some bubbles of a gas are seen when lead (Pb) is reacted with the acid. Explain these observations giving suitable reasons.