Final answer:
The presence of an insoluble substance, such as sand or charcoal, has no significant effect on the boiling point of a liquid.
Step-by-step explanation:
The presence of an insoluble substance, such as sand or charcoal, suspended in a liquid does not have a significant effect on the boiling point of the liquid. This is because the boiling point elevation is a colligative property, meaning it depends on the number of solute particles in the solution, not the chemical composition of the solute. In the case of an insoluble substance, the particles do not dissolve or contribute to the number of solute particles, so there is no detectable change in the boiling point.