As you note, I said the hole in the metal ring 'almost' always expands upon heating.

Upon heating under high pressures with sulfur, it gives the disulfide.

Upon heating, the Seebeck effect will initially drive a current.

Upon heating to 90C the green phase can change into the orange.

Steam and air are used as leavening agents when they expand upon heating.

In particular, most plastics will melt upon heating to a few hundred degrees celsius.

Upon heating above 350 C, it decomposes to cyanogen and water.

It also slowly decomposes in air at room temperature and explodes upon heating to 165 C.

Upon heating, the shape changes to its original.

Upon further heating, they gradually soften, which can be characterized by certain softening points.