Final answer:
In chemistry, 'leftovers' refer to excess or unused materials after a reaction. Tracers are used to track the movement of substances in scientific studies, including in organic chemistry.
Step-by-step explanation:
In the context of chemistry, the term 'leftovers' refers to excess or unused materials after a chemical reaction.
Chemical equations need to follow the principle of conservation of mass, which means that the number and types of atoms must be the same before and after the reaction.
Tracers, on the other hand, are used in scientific studies to track the movement or reaction of specific substances.
For example, in organic chemistry, tracers have been used to study the pathway of reactions in plants, such as the process of photosynthesis.