Question

which of the following is a reliable way to observe that a chemical change has occurred when two substances come in contact with one another? (1 point)
conduct a test to determine the chemical makeup of the molecules
test for the release of heat
monitor for the release of a gas
observe a color change

Explanation:

A chemical change results in a new substance with different chemical properties. Conducting a test to determine the chemical makeup of the molecules can definitively show if new substances have formed, which is a reliable sign of a chemical change. Heat release, gas release, and color - change can also be signs of a chemical change but are not as conclusive as a change in chemical makeup. For example, heat can be released in some physical changes (like dissolving some salts), gas can be released due to a physical change like boiling, and color - change can occur without a chemical reaction (like mixing colored dyes).

Answer:

conduct a test to determine the chemical makeup of the molecules