- Element 3 turns to a greenish color
- An element is a kind of substance
- Therefore, element 3 turning green is an example of a substance turning green

- Element 3 turning green is an example of a substance turning green
- If the color of a substance changes then a chemical change may have occurred
- Therefore, a chemical change may occur to element 3

Hence, a chemical change may occur to element 3
Question: Which is a chemical change?
Context: - Element 3 turns to a greenish color 
- An element is a kind of substance 
- If the color of a substance changes then a chemical change may have occurred