Answer
conduct a test to determine the chemical makeup of the molecules
Explanation
A change in which one or more new substances are formed is called a chemical change. A chemical change is also called a chemical reaction.
There are five signs of a chemical change namely:
i. Color Change.
ii. Production of an odor.
iii. Change of Temperature.
iv. Evolution of a gas (formation of bubbles)
v. Precipitate (formation of a solid).
Therefore, a reliable way to observe that a chemical change has occurred when two substances come in contact with one another is to conduct a test to determine the chemical makeup of the molecules.
