Spotlight Revision Practice Test

Mercury thermometers were largely replaced because of safety concerns. Mercury is a highly toxic heavy metal, and if a thermometer breaks or leaks, mercury can spread as small droplets and release vapor. Breathing mercury vapor or absorbing it through skin can pose health risks, especially for children, pregnant people, and those with sensitivities. Cleanup is tricky and can require special procedures to prevent contamination of surfaces or water supplies, which is why many places push for safer alternatives. Safer options like alcohol-filled or digital thermometers provide similar temperature readings with far lower health and environmental risks. The other choices don’t fit because mercury is not typically expensive, it is quite accurate, and it responds quickly enough for practical use; none of those factors drove the shift as strongly as the toxicity and environmental hazards.