What is not soot?

Ash is not considered soot. Soot primarily consists of fine black particles produced by the incomplete combustion of carbon-based materials, such as wood or fossil fuels. It is typically made up of a mixture of carbon, tar, and other chemical compounds and is largely responsible for the black residue commonly seen in chimneys and on surfaces after fires.

In contrast, ash is the inorganic residue that remains after the combustion process is complete. It is composed mostly of minerals and does not contain the carbon particles characteristic of soot. While cinder can be a product of burning materials and may contain some unburned carbon, it is different from soot because it includes larger, partially burned particles that are often found mixed with ash. Charcoal, on the other hand, is the product obtained from carbonizing wood or other organic materials and contains a significant amount of carbon, which aligns it more closely with soot. Smoke is a mixture of gases and solid particles that result from combustion and usually contains soot, among other components. Therefore, ash stands out as the correct choice for what is not soot due to its fundamentally different composition.