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Question: What kind of matter is fire?
Answer: Well, the short answer is that fire is made of photons, but then this would be the shortest answer of all scientific questions. A slightly longer answer is that fire is made of light and heat, but both light and heat are a form of photons. The actual situation is a little bit more complicated. The complication is really in the question: 'What are photons.' This question requires a longer explanation. Photons are the energy carriers of so-called electromagnetic disturbance or waves. Light is made of photons that have somewhat higher energy levels that can excite the retina of our eyes (the visual sense), so we can see light. Heat, on the other hand, is made of lower level energy photons that cannot excite our visual sense, but we can feel them as warmth. Heat is referred to as so-called infrared radiation. We all know that in the case of light, there are different colors. Each color is made of photons with slightly different energy levels (or energy spectrum), with blue light having the highest and red light with the lowest. Our eyes can distinguish slight energy differences in photons to display color.
Now a related question is: What causes the fire that is made of photons? The answer to this question is that there is a chemical reaction in burning wood or coal that causes electrons to jump around, and convert their energies to photons. This is related to a deeper concept that Einstein discovered almost 100 years ago, that energy could be converted to matter. So, by electrons jumping around, the excess energies given off by electrons change to matter, photons, thus presenting themselves as fire.
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