Initially:

- The ammonium metavanadate appears as a white powder

Stage 1:

- As you begin heating, the powder turns black and emits steam (moisture and ammonia)

- The black color is from the formation of vanadium (III) oxide (VO)

Stage 2:

- Continued heating leads to the formation of a brown viscous liquid

- This liquid undergoes a redox decomposition, releasing oxygen

Stage 3:

- The brown viscous liquid starts solidifying and transforming into a yellow-orange solid mass

- This solid is composed primarily of vanadium pentoxide (V₂O₅) and nickel vanadate (Ni₃(VO₄)₂)

Observations in table form:

| Temperature| Observation| Chemical Changes |

|---|---|---|

| Initial| White powder | Ammonium metavanadate (NH₄VO₃) |

| Stage 1| Turns black; emits steam| Formation of vanadium (III) oxide (VO) |

| Stage 2| Brown viscous liquid | Formation of vanadium pentoxide (V₂O₅) |

| Stage 3 | Yellow-orange solid mass| Formation of vanadium pentoxide (V₂O₅) and nickel vanadate (Ni₃(VO₄)₂) |