Coal burns with __________________.

Coal burns with glow only.

When coal burns, it does not produce a flame but emits a red or orange glow. This is because coal is a solid fuel that does not vaporize upon heating. Unlike substances that vaporize and produce a flame when heated, coal burns with only a glow.

The combustion of coal involves a chemical reaction between carbon and oxygen, resulting in the formation of carbon dioxide and the release of heat energy. However, due to the solid nature of coal, it burns without producing a flame, instead emitting a characteristic glow. 

In summary, coal burns with only a glow because it does not vaporize upon heating, distinguishing it from other fuels that produce a flame during combustion.