What causes a red glow when the iron and sulphur mixture is heated?
I think it is two fold. First the Fe filings are heated to an incandescent point, then the combination of Fe and S to produce Fes is an exothermic reaction and that produces the red orange glow with Fe until the all of the reaction has taken place.
The red glow observed when the iron and sulfur mixture is heated is due to a chemical reaction called thermite reaction. In this case, the mixture undergoes a reaction called the formation of iron(II) sulfide.
To understand why the red glow occurs, we need to understand the properties of the elements involved. Iron has a high reactivity, meaning it readily reacts with other substances. Sulfur, on the other hand, is a non-metal that reacts easily with metals under specific conditions.
When the iron and sulfur mixture is heated, the heat energy supplies the activation energy needed to initiate the reaction. As a result, the sulfur molecules dissociate into sulfur atoms, while the iron atoms react with the sulfur atoms to form iron(II) sulfide.
The red glow observed during this reaction is caused by the intense heat generated due to the exothermic nature of the thermite reaction. As the mixture reacts, a significant amount of heat is released, causing the mixture to glow red-hot. This red glow indicates the high temperature reached during the reaction.
It's important to note that the red glow is not directly caused by the formation of the iron(II) sulfide compound itself. Instead, it is a visual manifestation of the intense heat generated during the exothermic reaction between iron and sulfur.