Law of conservation of matter

:See also: Law of Conservation of Mass

Nuclear Processes

The Law of Conservation of Matter breaks down for nuclear processes, where the equivalence of matter and energy, and hence conservation of energy, applies.

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Law of Conservation of Matter: During an ordinary chemical change, there is no detectable increase or decrease in the quantity of matter.

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It is practical to use energy as a measure of matter. For kinematic reasons we have:

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The total quantity of matter and energy available in the universe is a fixed amount and never any more or less.

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An Exception to the Law of Conservation of Matter Modern nuclear chemistry has been successful in proving that in certain situations (a nuclear reaction, for example), matter can in fact be lost in the sense that the quantity of all matter remaining in the universe is less than what it was prior to the reaction taking place. This idea can best be summarized by the Einstein's equation which is E=MC^2, meaning that the total energy gained by a loss of M ,matter, is the product of m and the universal constant C, aka the speed of light or 3x10^8 m/s.

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Matter and Antimatter

Instead of counting atoms, another way is to count the particles atoms are made of. Atoms are made of protons, neutrons, and electrons. It is best to concentrate on nucleons (protons and neutrons) their number is the baryon number. There are more particles that also are baryons. The point is that the baryon number is conserved, so we can use this for the conservation of matter law. We can create more baryons (matter) from less as long as we create the same number of antibaryons (antimatter). The number of baryons minus the number of antibaryons (matter minus antimatter) is conserved in all experiments and so this can be a conservation of matter law.

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The universe has more matter than antimatter, as we see. If that is true, and all matter (and antimatter) is created at the big bang (from no matter), then matter is not conserved. (So protons can decay but their lives are very long)

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