Mercury is used in thermometers because of its unique physical and chemical properties that make it ideal for accurately measuring temperature changes. These properties include:
- Mercury remains liquid at room temperature with a wide temperature range, having a high boiling point (approximately 357°C) and a relatively low freezing point (-38.83°C), allowing it to measure a variety of temperatures without evaporating or freezing inside the thermometer.
- It has high thermal conductivity, which means it quickly responds to temperature changes, expanding or contracting almost instantly, leading to fast and accurate readings.
- Mercury expands uniformly and consistently with temperature changes and does not stick to the glass of the thermometer, allowing smooth movement of the mercury column for precise measurement.
- It is chemically stable, does not react with the glass or other materials, and can last for many years without deteriorating or giving inaccurate readings.
These factors combined made mercury the preferred choice in thermometers for centuries, though its use is declining due to health and environmental concerns with safer digital and alcohol-based alternatives now available.
