Final answer:
Evidences of a chemical reaction include a change in color, energy change (temperature or light), gas production, the formation of a precipitate, and changes in properties like smell or taste.
Step-by-step explanation:
Chemical reactions can be identified by a variety of signs. Some prominent evidence that indicates a chemical reaction has occurred includes:
- Change in color: This could be evident as one substance reacts and undergoes a change indicating the formation of a new substance with different properties.
- Energy change: This can be observed as either an exothermic reaction which releases heat, an endothermic reaction which absorbs heat, or a reaction that produces light.
- Gas production: Bubbles or fumes can be seen during a reaction, which is a telltale sign of gas being produced as a reaction proceeds.
- Formation of precipitate: A solid that forms and settles out of a liquid mixture is a clear indication that a new substance has formed during the reaction.
- Change in properties: This includes changes in smell, taste, or other observable properties that differ from the original reactants.
These results help scientists to confirm that chemical reactions have taken place and to understand the new substances that have formed as a result.