What is a Physical Change?
A physcal change is a phase change and is when a substance changes from one state (solid or liquid or gas) to another without a change in chemical composition.
What is a Chemical Change?
A chemical change is when the substance is altered chemically and displays different physical and chemical properties after the change. When a chemical change occurs, the new substance are formed through a reorganization of the atoms, and broken and new formed bonds. An example of this is when a tree rots, it is called decomposition, or when a bomb goes off, and that is called combustion.
Can They be Reversed?
A physical change is easy to reverse, you just need to reverse what you did in order to achieve the state. But a chemical change, is much much harder to reverse in most cases. Since the atomic structure is changed and bonds are broken and new bonds are formed, the process of reversing is much harder