What is the purpose of chemical properties of a substance:chemical reaction lab experiment?

Chemical properties can be simply stated as a kind of change where in the  initial material is not anymore present in the final outcome or after a reaction. There is a change in the substance' identity. Burning a piece of paper is a kind of chemical change because after the paper is completely burnt, you cannot see any the original identity of the paper before burning. Instead you see black residue.

For a chemical reaction lab experiment, the purpose of chemical change is to identify if there is a new substance formed.

For example, mixture A (color red solution) and then you add a solid B (color silver). Upon the reaction, you notice that the color of the solution is becoming color green and the size of the solid B is reducing. These are clearly evidences of chemical change. The color of the solution changes and the size of the solid decreases.