Mercury has a unique property that allows it to respond rapidly to temperature changes, unlike water. The reason for this lies in the physical characteristics and molecular structure of both substances.
Mercury is a metal that remains liquid at room temperature. Its atoms are closely packed but are less cohesive compared to water molecules. This means that when the temperature changes, the kinetic energy of mercury atoms increases quickly, leading to a rapid expansion or contraction. As a result, even a slight change in temperature can cause noticeable movement in a mercury thermometer.
On the other hand, water has a strong hydrogen bonding network among its molecules. These bonds make water molecules stick together more tightly, requiring a significant amount of energy to cause a change in temperature. Therefore, when the temperature shifts slightly, the changes in kinetic energy of water molecules aren’t as pronounced as in mercury. The bonds must first be overcome before water can either heat up or cool down, which is why it reacts more slowly to temperature changes.
In summary, mercury’s quick response to temperature changes is due to its weaker interatomic forces and liquid state at room temperature, while water’s strong hydrogen bonds require more energy to change temperature, leading to slower reactions.