Question

List 4 observations that suggest a chemical change is occurring

Answer 1

1. Creation of different compounds. (Since a chemical change is one in which the arrangement of atoms changes.)
2. Color change. ( Because if a new compound is formed, its color can be different from the original compound)
3. Cannot be reversed by reversing the condition. 
4. In most cases, a gas is formed. 

Answer 2

1. The evolution of energy
2. the production of a gas
3. the formation of a precipitate
4. color change