Most of us just accept that fact that food left in the freezer too long will eventually become covered in ice and almost inedible. But have you ever stopped to think about why that happens exactly? After all, it's not like everything in your freezer is completely thawing and refreezing every day.
The culprit here is sublimation, the process you learned about in grade school science whereby a solid turns directly into a gas. In this instance it's the frozen water in your food escaping as water vapor and then refreezing on the outside again. Which leaves food dry and tough, not technically burned. It's also the reason ice cubes seem to magically shrink, and why an abandoned freezer will slowly turn into a Hoth-like ice-covered cave.