The law of conservation of mass is the basic law of nature. Please explain why there is the law of conservation of mass from the micro point of view

The law of conservation of mass is the basic law of nature. Please explain why there is the law of conservation of mass from the micro point of view

Conservation of mass is for chemical reactions. In chemical reactions, chemical bonds in molecules break and become atoms. Then atoms combine to form new chemical bonds and release energy. Before and after chemical reactions, the total type and number of atoms do not change, so the total mass of matter is conserved. Welcome to inquire, hope to adopt, thank you!

According to the law of conservation of mass
1. The mass of solid increases after burning
2. After burning charcoal in the air, the solid mass becomes smaller

Magnesium combines with oxygen to form magnesium oxide, which is a solid, so its mass increases
And carbon and oxygen combine to form CO2, which turns into a gas. Of course, the mass of solid decreases