Video: Watch this demo
Description: This demonstration shows the thermal properties (thermal expansion) of two different metals.
- Bimetallic Strip
- Bunsen burner
- LN2 and container
- Connect the bun sen burner to the gas valve in the classroom.
- Light the Bunsen burner.
- Show students that the two strips are flat.
- Stick the bimetallic strip into the fire for several seconds until it bends.
- Show the students that the strip is bent. Since both sides of the bimetallic strip are color coded, tell the students what side it bent to.
- Place the bimetallic strip into some LN2 and wait a for it to cool down and bend.
- Show students that it is now bent the other way (towards the other color strip).
- This happens because one metal expands and contracts faster than the other.
- When finished, turn off the gas valve.
Keep away from flammable materials.
Use caution when working with liquid nitrogen, as it is very cold.