In the chemical change any two substance get mixed well the new substance form so this substance form only in the chemical change because in physical change is reversible

Explanation:
Chemical change refers to a process in which one or more substances undergo a transformation to form new substances with different chemical properties. In a chemical change, the molecules of a substance do change. Let's explore this further:

1. Definition of Chemical Change:
Chemical change, also known as a chemical reaction, occurs when the atoms or molecules of a substance are rearranged to form new substances. This rearrangement involves the breaking and forming of chemical bonds.

2. Reversibility:
Chemical changes are generally irreversible. Once a chemical reaction occurs, it is difficult or impossible to reverse the process and regain the original substances. This is due to the fact that the bonds between atoms are broken and new bonds are formed, leading to a different arrangement of atoms.

3. Molecules of a Substance Change:
During a chemical change, the molecules of a substance undergo a transformation. This can involve the breaking of existing bonds and the formation of new bonds. As a result, the arrangement and composition of atoms within the molecules change, leading to the formation of new substances.

4. Examples of Chemical Change:
There are numerous examples of chemical changes that occur in everyday life. Some common examples include:
- Combustion: When a substance burns, such as wood or gasoline, it undergoes a chemical change. The molecules of the substance react with oxygen in the air to produce carbon dioxide, water, and heat.
- Rusting: When iron is exposed to moisture and oxygen, it undergoes a chemical change known as rusting. The iron molecules react with oxygen and water to form iron oxide, which is a different substance with different properties.
- Digestion: In the human body, food undergoes chemical changes during digestion. Enzymes and acids break down complex molecules into simpler substances that can be absorbed and utilized by the body.

5. Substance Remain Same:
In a chemical change, the substances involved are transformed into new substances with different properties. The original substance no longer exists in its original form. The atoms and molecules rearrange themselves to form new compounds or elements.

Conclusion:
In summary, in a chemical change, the molecules of a substance do change. This change is usually irreversible, and the original substance is transformed into new substances with different properties. Understanding chemical changes is important in fields such as chemistry, biology, and materials science.