Question

9 which of the following is evidence of a chemical reaction? a change in temperature b change in mass c physical change d change from solid to liquid

Explanation:

• A change in temperature can occur during a chemical reaction due to the absorption or release of energy. For example, in an exothermic reaction (like combustion), heat is released, causing a temperature increase. In an endothermic reaction (like some decomposition reactions), heat is absorbed, causing a temperature decrease.
• A change in mass is not a valid indicator of a chemical reaction. According to the law of conservation of mass, in a closed system, the mass remains constant during a chemical reaction.
• A physical change (such as a change from solid to liquid, which is just a phase change) does not involve a chemical reaction. Physical changes do not result in the formation of new substances.

Answer:

A. change in temperature