All you need to understand is that in different environments matter behaves differently.

This forms a complex web of rules we call chemistry. I do not know half of the rules, and don’t enjoy studying it, but it’s essentially a study of how these base particles can build up to form these complex geometric patterns and small forces that always want to try and follow these rules.

Pressure, temperature, mass, composition, scale, molecular structure, atomic structure, and loads of other shit all affect these rules. Like, Oxygen at x temperature will want to turn to liquid. Oxygen at x temperature will turn gas. Oxygen at x pressure will want to be liquid. Well, it gets more complicated when they interact with eachother, as temperature and pressure are related. This gets even more complicated once you factor in that you aren’t just dealing with one type of element, and that elements also have rules with how they interact with eachother. Ex:Oxygen at x temperature and hydrogen at x temperature bond together to form water, which also does different things at different temperatures.

This can get insanely complex insanely fast. But the rules all must be followed. Sometimes this sets up a row of dominoes than can get knocked over because all of the rules line up in a way that cause a lot of this matter/bond stored energy to be released.

By exposing heat to this food, you can start a reaction that sustains itself like wood on fire.

Once you get that initial starting flame to burn, and as long as you keep giving enough molecules to burn, the wood at certain temperature pulls oxygen apart to create a different compound which is a little chemical reaction. A lot of times there are many chemical compounds created as it’s not easy to get a completely pure molecular compound. Smoke, ash, infrared heat, all of it is dispersed.

The overall governing rules that explain these things are the Laws of Thermodynamics, like conservation of energy. If you want to understand this better, spend time focusing on videos explaining chemical reactions and the laws of thermodynamics. Those are your googleable terms.

Food particles is a fairly unhelpful way to look at calorimetry. If you look at respiration or combustion the products are chemically more stable than the reactants. Carbon dioxide (gas) has stronger chemical bonds than sugar (solid). A house of cards is less stable than a collapsed pile of cards. Heat energy is released in both cases when they change.

So yes and no to it being that simple. For understandings sake, you can say that it is that simple, you burn the food, some energy is lost from the food as it turns into energy/matter in other forms(matter and energy can be converted to each other), the total amount of energy never changes, only where and how its stored. On the other end of the complexity spectrum, what actually is happening when you burn that food, is alot more meticulous, for anyone's liking, even the people who study things like molecular physics lol.