Final answer:
The four signs indicating a chemical reaction are a change of color, production of gas, formation of precipitate, and transfer of energy.
Step-by-step explanation:
Nonverbal communication is a form of symbolic communication that is learned through one's culture.
There are four visual clues or signs that indicate a gesture has occurred.
- A change of color occurs during the gesture.
- A gas is produced as a result of the gesture.
- A solid product called a precipitate is produced in the gesture.
- A transfer of energy occurs during the gesture.
When one or more of these signs are observed, scientists can infer that a chemical reaction is likely taking place. It's important to note that while these signs can indicate a reaction, they are not definitive proof, and further investigation is usually necessary to confirm that a reaction has occurred.