How to understand that the law of conservation of mass learned in chemistry class is wrong, this sen

In fact, learning itself is a matter of increasing precision.

For example, the physics problem is just to tell you the distance between the two points of ab and the speed of the ball, and find the time.

Later, gravitation was added, and there was a flat throwing motion. ab two points are no longer a straight line.

Later, the ball is no longer a particle, and the air resistance has to be considered.

Later, factors such as the rotation of the ball, the local altitude, the density of the air, and so on can be taken into account.

So we were wrong in the first place?

Not really. It just doesn't need to be so precise at first.

The same is true for conservation of mass. In middle and high school, books tell you that the quality is equal before and after the response. Although it is not actually equal, what is the difference between 1G and it?

But when it comes to college, when the book talks about nuclear reactions, this little bit of mass is very important, and the power of the nuclear bomb ** comes from this little bit of mass, so you can't ignore them at this time. <>

In fact, it is the law of conservation of mass and energy, e mc2. There is a change in energy before and after a chemical reaction, so there must be a change in mass. It's just that the mass change caused by the change in energy is very small, so it can be considered that the mass is unchanged before and after the reaction.

Conservation of mass is indeed wrong, and every time I drop a pen on the ground, I can't find it.

To be precise, it should be the law of conservation of mass and energy, and the conservation of mass alone or the conservation of energy is incorrect.

This sentence itself is wrong, chemical reactions do not cause changes in the nucleus, so the law of conservation of mass is observed, is it not ridiculous to draw in the picture? Combustion is the participation of oxygen in the reaction, and the gas released is not counted, how can it be conserved?

The chemical reaction is generally the conservation of atoms, compared with the loss of proton neutron binding energy in the nucleus, we can regard the formation of chemical bonds as no mass loss, so the chemical bond changes in mass unchanged, in fact, the chemical bond also has binding energy, but it is very low.

Chemical energy is also energy, exothermic reactions release energy, internal energy decreases, and mass is reduced, but much less than nuclear reactions.

I clearly remember that there is a row of small characters at the bottom of the section on conservation of mass in the chemistry book of the third year of junior high school, saying that it should be the conservation of mass and energy to be precise, so don't criticize it if you have nothing to do