Final answer:
When heating a liquid in a test tube, a student should always wear safety goggles, use a stopper, and record the temperature.
Step-by-step explanation:
When heating a liquid in a test tube, a student should always wear safety goggles. This is important to protect the eyes from any potential splashes or chemical reactions during the heating process.
Other safety precautions include ensuring proper ventilation in the laboratory, using a stopper to prevent any spills or accidents, and recording the temperature of the liquid to monitor changes during the heating process.