Question

Water plays a key role in the biosphere. It is due to certain properties of \(\mathrm{H}_{2} \mathrm{O}\) as compared to other liquids. These are except (a) higher specific heat (b) lesser thermal conductivity (c) high dielectric constant (d) high surface tension.

Short answer

The exception is (b) lesser thermal conductivity, because water actually has a higher thermal conductivity compared to many other liquids.

Step-by-step solution

Understanding the Properties of Water

Consider the unique properties of water that support life and compare them to other liquids. High specific heat allows water to absorb a lot of heat without significantly changing temperature. High dielectric constant enables water to dissolve many substances, making it an excellent solvent. High surface tension allows water to form droplets, which is important in various biological processes.

Identifying the Exception

Review each option and determine whether it is a property of water that is higher or more pronounced than in most other liquids.

Comparison with Other Liquids

Recognize that water does indeed have a higher specific heat, high dielectric constant, and high surface tension compared to many other liquids. These properties are essential for life. However, water has higher thermal conductivity than many other liquids, not lesser.

Key concepts

Specific Heat

Water's specific heat is one of its most remarkable properties, playing a pivotal role in maintaining stable ecosystems and climate. Specific heat is defined as the amount of heat per unit mass required to raise the temperature of a substance by one degree Celsius. The specific heat of water is exceptionally high compared to most other substances, which allows it to absorb and store large quantities of heat energy with minimal temperature change. This characteristic ensures that aquatic environments are less subject to temperature fluctuations, providing a stable habitat for marine life.

Likewise, the high specific heat capacity of oceans significantly influences the global climate by acting as heat reservoirs, moderating temperatures by absorbing heat in the summer and slowly releasing it during the winter. Understanding this property helps students appreciate the integral role water plays in ecosystem dynamics and in tempering the Earth's climate.

Thermal Conductivity

Thermal conductivity is a measure of a material's ability to conduct heat. Among liquids, water has a relatively high thermal conductivity, meaning that it can transfer heat effectively. This property is crucial in biological systems, where it allows for efficient distribution of heat. For instance, the human body uses the thermal conductivity of water in blood and tissues to maintain an even body temperature.

Contrary to the mistaken option in the exercise that suggests water has lesser thermal conductivity, it actually has a higher thermal conductivity when compared to most other liquids. This enables it to effectively transfer heat, which can be seen in phenomena such as the ocean's conveyance of thermal energy across the globe, significantly affecting weather patterns. When students understand thermal conductivity, they grasp why water is so effective in climate control and in organismal heat regulation.

Dielectric Constant

The dielectric constant, also known as relative permittivity, is a measure of a substance's ability to insulate charges from each other. Water has a high dielectric constant, which implies that it can reduce the electrostatic forces between charged particles. This property is particularly important because it allows water to dissolve a wide range of ionic and polar substances, earning it the moniker of 'universal solvent.'

In biological terms, this means water is essential for transporting nutrients and waste products in cellular processes. The high dielectric constant also plays a fundamental role in the structure and function of biomolecules like proteins and DNA, as it influences the formation of hydrogen bonds, a type of weak chemical bond critical for the maintenance of the three-dimensional structures of these molecules. By exploring the concept of water's dielectric constant, students develop an appreciation for its crucial role in chemical reactions and life-sustaining processes.

Surface Tension

Surface tension is a property that describes the elastic tendency of a fluid's surface to minimize its area. Water has a high surface tension due to strong hydrogen bonding between its molecules. This leads to phenomena like water droplets forming beads on surfaces, insects such as water striders walking on ponds, and the capillary action that allows water to move up thin tubes against gravity.

In the biological sphere, high surface tension is significant for processes like transpiration in plants, where water is pulled through tiny vessels. It also contributes to the efficient functioning of the alveoli in the lungs, where surface tension must be carefully regulated to allow for gas exchange. By understanding water's surface tension, students recognize its impact on both small-scale physical effects and critical biological systems.