Stories from Physics for 11-14 14-16
The anecdotal observation that alkaline batteries that are low on charge bounce higher than fully charged ones has been supported by the work of a team of American researchers.
When an alkaline battery is fully charged, the anode consists of zinc particles in an electrolyte matrix that allows the particles to move freely. As the battery loses charge, the zinc particles become encased in zinc oxide shells, restricting their movement. Connections between zinc particles grow, displacing water, allowing pressure waves to pass through more easily and increasing the height of bounce.