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

The correct answer is D. Change in volume

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.

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.