If a flat metal plate with a circular hole cut through it is heated, the hole ge

Question

If a flat metal plate with a circular hole cut through it is heated,
the hole gets smaller.

the hole gets larger.

the hole stays exactly the same size.
.

the hole may get larger or smaller, depending on the material of the plate.

the hole may get larger or smaller, depending on how much the plate is heated

the hole gets smaller

the hole gets larger.

the hole stays exactly the same size.
.

the hole may get larger or smaller, depending on the material of the plate.

the hole may get larger or smaller, depending on how much the plate is heated

the hole gets smaller

Explanation / Answer

It may seem counterintuitive, but the hole should grow bigger. The distance between atoms grows at the hole perimeter, and the atoms outside the perimeter also have room to expand outward. The distance between atoms grows everywhere. Since the distance between atoms at the hole perimeter grows, and the number of atoms does not change, the circumference should grow. Hence the width of the hole (proportional to the circumference) also grows.

If the hole size is much larger than the interatomic distance, this is the only stable solution, since pushing atoms inward would crowd them together (not favored at higher temperature).

The "wiggly ring of atoms" solution is also unstable, and eventually becomes a larger ring of atoms, corresponding to a larger hole size.

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