Is making glue an example ot a chemical change or a physical change? How do you know?
Depends what type of glue and how you make it.
You said “making glue” so I assume you mean the process of preparing a glue formulation, rather than using the glue to stick something together.
Some glues are simply solutions of a substance (polymer for example) in a solvent, others may require some sort of chemical reaction, so you would need to specify exactly how the glue is made.
However, in general terms if a change results in no different chemical species being created (no chemical bonds being broken or formed), then it’s a physical change. If any chemical reaction occurs so that new chemical species are formed, then it’s a chemical change.
Please note: designation of chemical or physical change is NOT related to reversibility.