Question

What difficulties might be encountered if water were used as the thermometric substance in a liquid-in-glass thermometer?

Answer 1

• The melting point of water is 0^oc but when you see mercury freezing point (melting point) -38.83^oc and the boiling point of the mercury is 356.73^oc. The boiling point of water is 100^oc. So based on these criteria the water has a low range of temperature scale.
• The color of mercury is silvery which is easy to identify and whereas water is transparent and there is a chance of reflections of various colors.
• The thermal expansion of mercury is 60.4 µm/(m·K) (at 25 °C). The thermal expansion of water is from 4 ^oC to 100 ^oC - 4.2x10^-2the volumetric temperature expansion is non-linear respective to the temperature. But the mercury is linear temperature expansion can be observed. This is one of the main reasons to use of mercury in thermometers.
• Water having the property of condensation but the mercury has no condensation property which is helpful to expect the exact values compared to water.
• We can measure the negative and positive temperature by using the mercury but water cannot. Water is not helpful to measure below 0^oC and above 100^oC.
• The mercury does not stick to capillary wall of thermometer and which can easily measure temperature accurately