Final answer:
A tracer is a substance used to monitor the presence and distribution of itself within an experiment. Radioactive isotopes like tritium and carbon-14 are often used as tracers due to their detectable radioactivity, which helps in studying biochemical reactions and diagnosing medical conditions.
Step-by-step explanation:
A tracer is the correct term for a substance that reveals its presence in one way or another and thus can be localized or monitored during an experiment. One common type of tracer is a radioactive isotope, which can be detected far from its original source, allowing scientists to trace the path of certain chemicals. For example, Hydrogen-3 (tritium) can be used to trace the path of water underground. When tritium-containing water is run through water pipes, any leaks can be detected using a Geiger counter to locate the radioactive tritium in the ground around the pipes. Tritium's ability to be detected due to its radioactivity makes it an effective tracer.
Moreover, radioactive tracers are especially useful in the study of biochemical reactions and in medical applications for both diagnosis and treatment. In research, a radioactive tracer such as carbon-14 (14C) can be used to follow steps of complex chemical reactions, like photosynthesis in plants, as it helps scientists see where the carbon atoms move throughout the process.