Question

Doesactionof heat on sodium nitrate is a physical change or a chemical change or both

Answer 1

The following reactions takes place on heating of sodium nitrate.
2NaNO₃ $\to$2NaNO₂ + O₂
​The starting material NaNO₃ is white solid but the product formed NaNO₂ is ​white to slightly yellowish crystalline powder. So, although the both the starting and products are solid but their is change of colour. That is a physical change. More over new products are formed after the reaction which is different from the starting material. That is a chemical change.
Hence heating of NaNO₃ shows physical as well as chemical change.