What is a physical change and how do you know it happened?

A physical change is defined as "a usually reversible change in the physical properties of a substance,as size or shape" so its basically a change of a substance that you can see. You know a physical change has occurred if a substance has changed size or shape or in a way that you can physically see.

A physical change is when somebody smashes a computer screen. It's physical because the looks are changing of the computer. Hope this helps!

I think its called a compound

Explanation:

2 or more different particles is called a compound.