Did you know there is a simple test you can do to see if an alkaline battery is fresh or dead?^1,2 All you need to do is bounce the bottom of a battery onto a hard, flat surface. If the battery is fresh it won’t bounce very well. If the battery is dead, it will bounce very high. Check it out in the video.³

Guess what causes this difference in bouncing ability between fresh and dead batteries? Chemistry, of course!

The chemical reaction that powers batteries involves the conversion of zinc metal, manganese (IV) oxide and water into zinc oxide and manganese oxide hydroxide:^1,2

Zn(s) + 2 MnO₂(s) + H₂O(l) à ZnO(s) + 2 MnOOH(s)        Equation 1

It turns out that ZnO is a very bouncy material. Indeed, adding ZnO to the interior of golf balls increases the distance they travel when they are hit.⁴ Thus, the formation of increasing amounts of ZnO as a battery is used increases the bounciness of the battery. Notice that water is also consumed as a battery is used. This also probably contributes to the increased bounciness of a dead battery in the following way: when a dropped battery strikes a surface, its kinetic energy of motion can be more easily dispersed throughout a liquid than a solid. Thus, the water present in a fresh battery leaves less kinetic energy for rebound. This water is consumed as the battery is used, causing the interior of a dead battery to be more-solid like. Less liquid water available in a dead battery does not allow for such kinetic energy to be dispersed, leaving more energy for rebound.

In addition to differences in bouncing ability, it is quite easy to compare differences in the contents of fresh and dead batteries. To do so, try cutting open a fresh and a dead battery with a pair of PVC pipe cutters to inspect the differences between the two (SEE CAUTION BELOW). You will likely note that a fresh battery oozes a bit upon cutting it open, while a dead battery does not. This observation is consistent with the fact that water is consumed as a battery operates (Equation 1). You might notice that the inner portion of a fresh batter appears to be more silvery in color, while the inner portion of a dead battery appears more whitish grey. These observations are consistent with the conversion of Zn to ZnO as a battery operates: zinc is a silvery metal, while zinc oxide is white.

It is also possible to use a simple chemical test to distinguish between the presence of Zn and ZnO in fresh and dead batteries. The inner portion of fresh batteries reacts with hydrochloric acid to produce a gas. Again, that’s because the inner portion of fresh batteries contains a lot of unreacted Zn metal:

Zn(s) + 2HCl(aq) à ZnCl₂(aq) + H₂(g)                     Equation 2

However, the inner portion of a dead battery contains mostly ZnO, which produces no gas upon reaction with hydrochloric acid:

ZnO(s) + 2 HCl(aq) à ZnCl₂(aq) + H₂O(l)               Equation 3

Because of this difference, one would expect larger gas H₂ production when mixing the inner portion of fresh batteries vs. dead batteries with HCl(aq).

The video below illustrates how to carry out these particular experiments.

I hope you consider trying out these experiments in your classroom. Drop a note in the comments if you try them out for your students. Happy experimenting!

CAUTION: Wear safety goggles and gloves. The experiments described herein are only intended for Zn-MnO₂ alkaline batteries. Do not attempt to cut open any other type of batteries as the contents very likely contain hazards not described here. The contents of Zn-MnO₂ alkaline batteries contents are caustic. Use caution when cutting open as the contents may spray. If the battery appears to be getting very warm when being cut open, stop cutting immediately and promptly remove the PVC cutter from the battery.

References

1. Bhadra, S.; Hertzberg, B. J.; Hsieh, A. G.; Croft, M.; Gallaway, J. W.; Van Tassell, B. J.; Chamoun, M.; Erdonmez, C.; Zhong, Z.; Sholkapper, T.; Steingart, D. A. The relationship between coefficient of restitution and state of charge of zinc alkaline primary LR6 batteries. J. Mater. Chem. A. 2015, 3, 9395–9400.

2. Hall, J. M.; Amend, J. R.; Kuntzleman, T. S. Experiments To Illustrate the Chemistry and Bouncing Ability of Fresh and Spent Zinc–Manganese Oxide Alkaline Batteries. J. Chem. Educ. 2016, 93, 676-680.

3. Kuntzleman, T. S. Chemistry of the Battery Bounce Test, Tommy Technetium YouTube Channel, published 2/1/2019. (accessed 3/27/19).

4. Sullivan, M. J.; Nesbitt, R. D. Golf Ball Comprising a Metal, Ceramic, or Composite Mantle or Inner Layer. 2003, U.S. Patent 6,612,939 B1.