This is related to a biology lab I did. What is the purpose of adding sand to hydrogen peroxide (and put at a glowing splint at the mouth of the tube)?

The purpose of this lab was to study the action of the enzyme catalase (potato)on hydrogen peroxide and to determine the conditions that affect this activity.

Thanks in advance.

Sand + H2O2 is a non-reactive mixture. The catalase test will froth in peroxide if present. The sand may have been a test of total inertness.