What are Methods scientists use to determine if a change was physical or chemical?

The difference between a physical reaction and a chemical reaction is composition. In a chemical reaction, there is a change in the composition of the substances in question; in a physical change there is a difference in the appearance, smell, or simple display of a sample of matter without a change in composition.

Explanation:

Examples of Physical Changes;

Boiling water.

Mixing sand and water.

Example of chemical changes;

burning, cooking,

rusting, and rotting.

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.

the answer is a and have a great day