Question

what does a chemical indicator do?
change temperature to show that certain substances are present.
change color to show that certain substances are present.
cause an explosion when certain substances are present.

Explanation:

Chemical indicators are substances that undergo a visible change (such as a color change) in the presence of specific substances. Temperature change is not the typical mode of action for chemical indicators, and causing an explosion is not a characteristic property of chemical indicators.

Answer:

Change color to show that certain substances are present.