The microcystaline structure of a steel wire changes from body-centered-cubic to face-centered-cubic as it is heated to red-hot.
What it shows:
Iron atoms are arranged in a body-centered cubic pattern (BCC) up to 1180 K. Above this temperature it makes a phase transition to a face-centered cubic lattice (FCC). The transition from BCC to FCC results in an 8 to 9% increase in density, causing the iron sample to shrink in size as it is heated above the transition temperature.
Here we set up a convection cycle, where we heat part of a fluid; it expands, rises, then cools and sinks. A two dimensional model for real convection cycles in the atmosphere, oceans or stellar interiors.
How it works:
The convection cell is made from two sheets of 0.5cm plexiglass (front clear, rear translucent), separated by a 0.5cm gap for the liquid, the indicator thymol blue. The sides are plexi and the top left open, but the bottom is sealed with a hollowed brass rod. The brass serves two purposes. Firstly...