system
Given the following post, respond as if you're commenting on Reddit:
human
If you dissolve a compressed spring in an acid where does the energy go?

You don't allow the spring to naturally go back to its normal, uncompressed, position (dissolving/disintegrating it before that point). The conservation of energy holds, so how/where does the energy go?
gpt
The energy is converted to heat.  

Many people are stymied by this question because they assume that it's possible to hold a spring in one position while it is entirely dissolved away.  This won't happen.  

As the spring is slowly dissolved away, it won't be as well contained by whatever mechanism was once holding it in a compressed state.  As this occurs, areas of the spring will relax.  By the time all of it is oxidized, all stress will have been released. The spring will pop or jostle as material is removed, and the energy contained is released as kinetic energy (motion) which is then converted to heat.  

But what if you keep compressing it so it can't move?  Well, you can't.  Even if you had a clamp and kept tightening it down to keep the spring "motionless", the atoms that make up the crystal structure of the spring are still able to move.  When the spring is compressed, energy is stored in the bonds between each atom in the crystal structure.  As each of those atoms are oxidized and removed from the structure, the bonds around it relax - this relaxation is the release of energy as motion or heat (the two terms are basically interchangeable at the atomic scale.)

TL:DR, the energy goes to motion/heat.  It doesn't happen all at once, but gradually as the metal is oxidized away.