When copper sulfate (CuSO₄) is heated, a series of changes occur depending on the temperature:

1. Dehydration (below 150°C):

* Change: Copper sulfate pentahydrate (CuSO₄·5H₂O), the most common form, loses its water of crystallization.

* Observation: The blue crystals turn white and powdery.

* Reaction: CuSO₄·5H₂O → CuSO₄ + 5H₂O

2. Decomposition (above 650°C):

* Change: Anhydrous copper sulfate (CuSO₄) decomposes into copper(II) oxide (CuO) and sulfur trioxide (SO₃).

* Observation: The white powder turns black.

* Reaction: CuSO₄ → CuO + SO₃

Summary of Changes:

| Temperature Range | Change | Observation |

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

| Below 150°C | Dehydration | Blue crystals turn white and powdery |

| Above 650°C | Decomposition | White powder turns black |

Note: The exact temperature at which these changes occur may vary slightly depending on factors such as heating rate and atmospheric pressure.