Question

what are indicators?
chemical compounds used to detect the presence of other compounds
molecules that give off a smell to help identify substances
machines that give readings of temperature, color, and ph
atoms that bond with substances and give off heat

Explanation:

Indicators are chemical compounds that change color or other properties to detect the presence of substances, typically in acid - base reactions or other chemical tests. They are not related to smell - giving molecules, machines, or heat - giving atoms in the context of their definition.

Answer:

chemical compounds used to detect the presence of other compounds