Final answer:
Boiling sticks should be added before heating a liquid to provide nucleation sites for bubble formation, ensuring even boiling and preventing bumping.
Step-by-step explanation:
Boiling sticks, also known as boiling chips, should always be added before heating a liquid. The purpose of boiling sticks is to provide nucleation sites that help in the formation of bubbles, ensuring that the liquid boils evenly and prevents bumping, which could potentially be dangerous. Bumping is a laboratory phenomenon where a liquid superheats and then rapidly boils, causing the liquid to spurt out of the container.
When a boiling stick is added before heating, it allows for better distribution of heat and helps prevent the superheating of the solution. If added after the liquid has started to heat, the sticks might not perform effectively, as the liquid may already be superheated, increasing the potential for bumping.
Therefore, the correct option in reference to when to add boiling sticks is: C) Before.