An engineer heats three different materials in an industrial kiln set to 950 ∘C950\ ^\circ\text{C}950 ∘C and records their states of matter at three stages of the process.
| Material | Before heating (at 20 ∘C20\ ^\circ\text{C}20 ∘C) | At 950 ∘C950\ ^\circ\text{C}950 ∘C | After cooling to 20 ∘C20\ ^\circ\text{C}20 ∘C |
|---|---|---|---|
| Alumina crucible | Solid | Solid | Solid |
| Silver solder | Solid | Liquid | Solid |
| Wet ceramic slip | Liquid | Solid | Solid |
Give a reason why the alumina crucible did not change state during this process.
