Bimetal Snap Disc - Changes shape when heated or cooled
Video of the sample from physicsfun
This disc is made from a laminate of two different metal alloys with different coefficients of thermal expansion. The disc changes instantly from a concave to a convex shape when it is heated above its activation temperature. It changes back again when it cools.
The movement of snap discs is used to make and break circuits, indicate or compensate for temperature changes, release springs, or control valves. The discs are found in electric kettles, shower controls, and cooling systems.
The sample is made from a layer of invar (low expansion) and a layer of steel (high expansion). Discs can be made with activation temperatures ranging from -40°C to 450°C.
The disc will jump half a meter into the air if placed on a flat surface with the sticker facing downward and then heated with a heat gun or a gas torch to above 40°C. It will snap back to its former shape when it cools down.
The product is also known as Jumping Discs
All samples come with a laminated information card, which includes contact details for the supplier.
Check this video: