Final answer:
Boiling stones are added to liquids to prevent bumping or superheating. They provide nucleation sites for the liquid to start boiling from. If you forgot to add a boiling stone while heating a liquid, you can add it once the liquid is close to its boiling point.
Step-by-step explanation:
Boiling stones are added to liquids to prevent bumping or superheating. Bumping occurs when the liquid becomes superheated and suddenly boils violently, causing the liquid to splash out of the container. Superheating happens when the liquid is heated beyond its boiling point without actually boiling. To prevent these issues, boiling stones can be added to provide nucleation sites for the liquid to start boiling from.
In the case where you forgot to add a boiling stone while heating a liquid, you can add it once the liquid is close to its boiling point. This will ensure that the boiling stones are present when the liquid reaches its boiling point and prevent bumping and superheating.