Question

Which of the following would not necessarily indicate a chemical reaction?

change in temperature
chemical precipitation of a solid
production of a gas
change in volume

Answer 1

Change in volume. A change in volume could indicate a chemical reaction, however a substance's volume could also change as a result of a change in temperature or pressure, therefore alone cannot be definitive evidence of a chemical change.

Answer 2

The correct answer is D. Change in volume

Step-by-step explanation:

In a chemical reaction, new substances are formed and as a result, the original substances or reactants change chemically. This is the opposite of a physical change that involves only a change in physical properties, but not chemical ones.

In the case of volume, this is a physical property and refers to the space a substance occupies. Due to this, a change in volume is related to a physical change, but not a chemical one. For example, if you compress a gas, this reduces its volume, but the gas will not change its identity or properties. This implies a change in volume does not necessarily indicate a chemical reaction, but it indicates a physical change.