Suppose that a substance in a beaker is heated over a burner in a science lab. Which observation would most likely indicate that a chemical change has occurred in the substance?

Question

If the substance is a liquid or solid, an increase in temperature would indicate a chemical change.
If the substance is a liquid, a change of some of the liquid to gaseous form would indicate a chemical change.
If the substance is a solid, a change of some of the solid to liquid form would indicate a chemical change.
If the substance is a liquid or solid, production of an odor would indicate a chemical change.

Answer 1

Among the options provided, the observation that would most likely indicate that a chemical change has occurred in the substance is:

If the substance is a liquid or solid, production of an odor would indicate a chemical change.

Production of a new odor often signifies that a new substance is being formed, which is a hallmark of a chemical change. The other observations, such as changes in temperature, state (liquid to gas or solid to liquid), can also occur during physical changes or phase transitions and do not necessarily indicate a chemical change on their own.