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.

answer; the numbers of valence electrons in the acetic acid molecule (ch3co2h) is 24;