Please explain the physical and chemical changes from a molecular point of view

The so-called chemical change refers to the change in the formation of new chemical bonds when there is a break of a chemical bond (the definition of a chemical bond in high school is the force that binds ions or atoms together, generally including covalent bonds, ionic bonds, etc.).

As for physical change, it generally refers to the change that no chemical bond break or formation has occurred, that is, no new matter is formed at the molecular level, which generally involves the change of kinetic energy and potential energy of the molecule.

It should be noted that nuclear reactions are not classified as chemical changes, because chemical reactions do not involve changes at the atomic level, chemical reactions only change the forces between atoms, and the atoms of substances in nuclear reactions have changed (for example, there are more protons and less neutrons), although new substances are generated, but they do not belong to the category of chemical reactions, and people currently classify them in the category of force and become nuclear physics.

That's probably the case, but I'm actually pretty unreliable. And now the definitions of all kinds of things are different at different levels of education. So it's best to ask the teacher about this kind of question.

Physical changes do not change molecules, such as water solidifies into ice, or H2O, chemical changes produce new molecules, and old molecules disappear.

When a substance composed of molecules undergoes a physical change, the molecules do not change, and no new molecules are produced, but the intervals between the molecules change; When a chemical change occurs, the molecule changes and decomposes into a new molecule, and the atom re-aligns into a new molecule.

So the answer is: physical change does not produce new molecules Chemical changes produce new molecules, and the molecules themselves change

Summary. Hello, the molecule itself of a substance does not change when a physical change occurs, the molecule itself changes when a chemical change occurs, and the essence of a chemical change is the creation of a new molecule

In physical change, the molecule itself of the substance itself is chemically changed when the chemical change occurs

Hello, the molecule itself of the substance does not change when the physical change occurs, and the molecule itself changes when the chemical change occurs, and the essence of the chemical change is to produce a new molecule

This question is to explain physical and chemical changes from a molecular point of view, where physical changes do not produce new molecules, and chemical changes produce new molecules

Physical change: no atomic exchange occurs, no new molecules are formed, or changes occur inside the atom, new atoms are created.

Chemical change: Atoms are exchanged to form new molecules.

Pure substance: An object made up of the same molecule.

Mixture: A mixture of different hollow-resistant molecules, even if it is composed of the same element, the same atomic composition is also a mixture, such as a mixture of carbon and diamond.

Concept of Molecule: A molecule is the smallest particle that maintains the chemical properties of a substance.

Concept of Atom: An atom is the smallest particle in a chemical change.

The essence of chemical change is that in a chemical reaction, the molecule is divided into atoms, the atoms can no longer be divided, and the atoms are recombined.

The similarities between a molecule and an atom.

They are all particles that make up matter, very small in mass and volume, separated from each other, constantly moving, both different types and numbers, and not electrically significant.

Molecules are different from atoms.

Molecular primitives.

1) A molecule is the smallest particle that maintains the chemical properties of a substance (1) An atom is the smallest particle in a chemical change.

2) The type of molecules must change in chemical changes, and the number may change (2) The types, numbers, and masses of atoms do not change in chemical changes.

3) The chemical properties of a substance composed of molecules are maintained by molecules (3) The atoms in a substance composed of molecules do not maintain the chemical properties of the substance. In a substance that is directly composed of atoms, the atoms maintain the chemical properties of the substance.

4) Expressed by chemical formula (4) Represented by element symbol.

5) Molecules are made up of atoms of the same or different species (5) Molecules are made up of protons, neutrons, and extranuclear electrons.

6) can exist independently (6) in most cases combined with each other and exist in molecules.

Note: Molecules are smaller than molecules compared to the atoms that make up such molecules, but not all atoms are necessarily smaller than molecules. For example, in the smallest hydrogen molecule, a molecule contains a total of 2 protons and 2 electrons, and its volume and mass are not as large as oxygen atoms.

An oxygen atom contains 8 protons, 8 neutrons and 8 electrons.