Answer:
The phlogiston theory was a scientific theory proposed in the 17th century to explain combustion (burning) and other chemical processes involving combustion, such as rusting. According to this theory, a substance called phlogiston was contained within combustible materials, and was released during combustion. This theory explained why metals became heavier when they were heated, since the phlogiston was thought to be a negative weight substance.
In contrast, the modern explanation of burning is based on the process of oxidation. Combustion occurs when a substance reacts with oxygen gas in the air, producing heat and light. In this process, the bonds between the atoms in the fuel are broken, and the atoms recombine with oxygen to form new molecules, releasing energy in the form of heat and light.
Overall, the phlogiston theory was disproven by experiments and observations made in the late 18th and early 19th centuries, and the modern explanation of burning is now widely accepted.
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