Question

Mixing of iron fillings and powdered sulphur is a physical change but heating this mixture is a chemical change ​

Answer 1

Explanation:

When iron filings and sulphur powder are mixed and heated they undergo a chemical reaction and form ferrous sulphide (FeS). It is a new substance which has properties entirely different from Fe and S. Therefore, heating of mixture of iron and sulphur powder is a chemical change.

Answer 2

mixing iron fillings with sulphur does not react with each other under ordinary temperature. as the ionisation energy(energy needed to knock a Valence electron by the electrostatic force) of iron is comparatively high. so it doesn't react with sulphur.

but heating this mixture to a certain high temperature will undergo a chemical reaction which led to a formation of iron and sulphur salt which is a new product so it is a chemical change.