Does everything have a chemical energy store?
In: Physics
In chemistry we talk about potential energy of different compounds, and it’s related to the bonds between atoms. When a bond is formed energy is released, and you need to add energy to break bonds. Different compounds are more or less stable and the potential energy is inversely proportional to the stability of the bonds.
As a metaphor, you can imagine a bowling ball on a shelf. The higher you put it, the more potential energy it has. But when it’s on the floor it is completely stable because it can’t fall any further and thus it doesn’t have any potential energy.
EDIT: a better metaphor would be magnets. It takes energy to separate magnets just like molecules, and when release the magnets so they snap together, that energy is released. You can actually hear that energy because it causes the air to move, i.e. you hear a sound (a click).
Chemical reactions that release a lot of energy (e.g. combustion) occur when you transition from a less stable to a more stable compound. Because you have to break the bonds of the original compound in order to get to the more stable one, all chemical reactions that don’t start out with unbounded atoms require some energy to start the reaction, but once it gets going it continues by itself. That’s why you need heat to start a fire, but once it gets going it usually continues by itself.
In theory, there are compounds that are the most stable combination of elements and thus do not have any potential energy.
Chemical energy comes from breaking a weak, unstable bond and forming a strong, stable bond. If a molecule already has a very stable bond, it’s very hard to extract energy from it. That doesn’t mean there’s no energy there, just that you can’t use it.
Think of it like water behind a dam. The farther the water can fall, the more energy you can get from it. If your dam is very tall, you can get a lot of energy. Once the water reaches the ocean, it can’t fall anymore unless you add energy to lift it back up, like waves or the tide or the water cycle.
The water in the ocean may be really high above the bottom, but it can’t *fall* so you can’t get that energy.
Some molecules, like hydrogen peroxide are really unstable. Oxygen doesn’t like to touch like that. Water, on the other hand, is very stable, because oxygen *really* likes to grab onto other atoms. If you add sodium, though, it will rip apart the water to make an even more stable molecule, releasing energy.
Eventually, you’re going to get to a molecule that’s too stable and the only way to get energy out is to put more in.
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