Is it true that a chemical property is a property that can be measured or observed only when matter undergoes a change to become an entirely different kind of matter

No, not really.

Explanation:

A chemical property cant be said to have taken place by mere seeing and touching the object.

In other words, a chemical property of a substance can be defined as a quality obtained by changing the substance to a new identity, both physically and within the internal structures. So the internal structures of the substance must be investigated to affirm a chemical change.

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme

this age may represent the age of the earth's accretion, of core formation, or of the material from which the earth formed. this dating is based on evidence from radiometric age-dating of meteorite material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples.