4 Properties Of Water That Are Important To Life

Water, the elixir of life, is more than just a thirst quencher; it's a cornerstone of existence on Earth. Its unique properties are fundamental to the survival of all living organisms, shaping environments and enabling biological processes. Let's delve into the four key properties of water that make it indispensable for life: its cohesion and adhesion, its exceptional ability as a solvent, its high heat capacity, and its unique density behavior.

Cohesion and Adhesion: Water's Sticky Nature

One of water's remarkable characteristics is its ability to stick to itself and other substances, a phenomenon arising from its polar nature.

The Science Behind It

Water molecules (H2O) are composed of two hydrogen atoms and one oxygen atom. Oxygen is more electronegative than hydrogen, meaning it attracts electrons more strongly. This unequal sharing of electrons creates a slight negative charge (δ-) on the oxygen atom and slight positive charges (δ+) on the hydrogen atoms. This charge difference makes water a polar molecule.

Because of this polarity, water molecules are attracted to each other. The slightly positive hydrogen atom of one water molecule is attracted to the slightly negative oxygen atom of another. This attraction is called a hydrogen bond. Although individually weak, the sheer number of hydrogen bonds between water molecules results in significant cumulative strength.

Cohesion: Sticking Together

Cohesion refers to the attraction between molecules of the same substance. In water, this means water molecules stick to each other. This strong cohesion gives water a high surface tension, which is the measure of how difficult it is to stretch or break the surface of a liquid.

Importance to Life:

• Water Transport in Plants: Cohesion is crucial for the transport of water in plants. Water evaporates from the leaves in a process called transpiration. As one water molecule evaporates, it pulls on the next, drawing water up from the roots through the plant's vascular system. This is known as the cohesion-tension theory. Without cohesion, water would not be able to defy gravity and reach the tops of trees.
• Surface Tension and Habitat: Water's high surface tension allows small insects, like water striders, to walk on the surface of ponds and lakes. This provides a unique habitat for these creatures and contributes to the overall biodiversity of aquatic ecosystems.
• Formation of Water Droplets: The cohesive forces between water molecules cause water to form droplets. This is essential for precipitation and the distribution of water across the globe.

Adhesion: Sticking to Other Things

Adhesion is the attraction between molecules of different substances. Water's polarity allows it to form hydrogen bonds with other polar molecules and surfaces.

Importance to Life:

• Capillary Action: Adhesion, along with cohesion, contributes to capillary action. This is the ability of water to move up narrow tubes against the force of gravity. Water molecules adhere to the walls of the tube, and cohesion pulls other water molecules along. Capillary action is vital for drawing water up the thin xylem tubes in plants.
• Water Retention in Soil: Adhesion allows water to cling to soil particles. This keeps the soil moist and provides water for plant roots.
• Lubrication: Water's adhesive properties make it an excellent lubricant. It reduces friction between surfaces in living organisms, such as in joints.

Water as a Solvent: The Universal Dissolver

Water is often called the "universal solvent" because it can dissolve a wide range of substances. This ability is critical for transporting nutrients and removing waste products in living organisms.

How Water Dissolves Substances

Water's solvent properties stem from its polarity. When a substance is dissolved in water, water molecules surround and separate the individual molecules or ions of the substance. This process is called hydration.

• Ionic Compounds: Water is particularly good at dissolving ionic compounds, such as salt (NaCl). The positive hydrogen ends of water molecules are attracted to the negative chloride ions (Cl-), while the negative oxygen ends are attracted to the positive sodium ions (Na+). This attraction overcomes the ionic bonds holding the salt crystal together, and the ions are dispersed in the water.
• Polar Molecules: Water also dissolves other polar molecules, such as sugars. These molecules have regions of positive and negative charge that can interact with water molecules.
• Non-Polar Molecules: Water does not dissolve non-polar molecules, such as fats and oils. These molecules lack charged regions and cannot form hydrogen bonds with water. This is why oil and water don't mix.

Importance to Life:

• Nutrient Transport: Water dissolves nutrients, such as sugars, amino acids, and minerals, and transports them throughout living organisms. This allows cells to access the building blocks and energy they need to function. In plants, water carries dissolved minerals from the soil to the leaves. In animals, blood (which is mostly water) carries oxygen and nutrients to cells.
• Waste Removal: Water dissolves waste products, such as urea and carbon dioxide, and removes them from the body. This prevents the buildup of toxic substances that can harm cells. In animals, the kidneys filter waste products from the blood and excrete them in urine.
• Chemical Reactions: Many biochemical reactions occur in aqueous solutions. Water provides a medium for reactants to meet and interact. For example, enzymes, which catalyze biochemical reactions, function in water-based environments.
• Maintaining pH Balance: Water plays a role in maintaining the pH balance of living organisms. It can act as both an acid and a base, helping to buffer changes in pH.

High Heat Capacity: A Temperature Regulator

Water has a high heat capacity, which means it can absorb or release a large amount of heat without undergoing a significant change in temperature. This property is crucial for maintaining stable temperatures in living organisms and aquatic environments.

The Science Behind It

Heat capacity is the amount of heat that must be absorbed or lost for 1 gram of a substance to change its temperature by 1 degree Celsius. Water has a high heat capacity because much of the energy is required to break the hydrogen bonds between water molecules.

When heat is added to water, some of the energy is used to disrupt hydrogen bonds before the water molecules can move faster (increase their kinetic energy) and raise the temperature. Conversely, when water cools, hydrogen bonds form, releasing heat and slowing the temperature decrease.

Importance to Life:

• Temperature Regulation in Organisms: Water's high heat capacity helps organisms maintain a stable internal temperature. This is particularly important for warm-blooded animals, which need to keep their body temperature within a narrow range to function properly. Water in the blood absorbs heat generated by metabolic processes, preventing the body from overheating. Sweating is also an example of how water's high heat of vaporization (related to its high heat capacity) helps cool the body. As sweat evaporates, it absorbs heat from the skin.
• Stabilizing Aquatic Environments: Water's high heat capacity helps stabilize the temperature of aquatic environments. Large bodies of water, such as oceans and lakes, can absorb large amounts of heat during the day and release it slowly at night. This prevents drastic temperature fluctuations that could harm aquatic organisms.
• Climate Moderation: Water's high heat capacity also influences regional and global climates. Coastal areas tend to have milder climates than inland areas because the ocean absorbs heat during the summer and releases it during the winter.

Density Behavior: The Solid That Floats

Unlike most substances, water is less dense as a solid (ice) than as a liquid. This unusual property has profound implications for life in aquatic environments.

The Science Behind It

When water cools, the molecules slow down and pack closer together, increasing the density. This continues until water reaches 4°C. Below this temperature, water begins to form crystalline structures as hydrogen bonds become more rigid. These structures create spaces between the molecules, causing the volume to increase and the density to decrease.

Ice is about 9% less dense than liquid water, which is why it floats.

Importance to Life:

• Insulation of Aquatic Environments: When lakes and oceans freeze, the ice forms a layer on the surface. This layer of ice insulates the water below, preventing it from freezing solid. If ice sank, bodies of water would freeze from the bottom up, making it impossible for aquatic organisms to survive.
• Habitat for Aquatic Organisms: The layer of ice on the surface of a frozen lake or ocean provides a habitat for certain organisms, such as polar bears and penguins. These animals can use the ice for hunting, resting, and breeding.
• Seasonal Turnover in Lakes: In temperate climates, lakes undergo seasonal turnover, where the surface water mixes with the deeper water. This process is driven by changes in water density as the temperature changes. Turnover brings nutrients from the bottom of the lake to the surface, promoting the growth of algae and other aquatic plants. It also oxygenates the deeper waters, allowing fish and other organisms to survive.
• Erosion and Weathering: The expansion of water as it freezes can cause rocks to crack and break apart. This process, called frost wedging, contributes to erosion and the formation of soil.

Conclusion: Water is Life

The four properties discussed—cohesion and adhesion, its solvent capabilities, high heat capacity, and unique density behavior—highlight water's critical role in supporting life on Earth. Without these properties, life as we know it would not exist. From the smallest microorganisms to the largest whales, all living organisms depend on water for survival. Understanding these properties is essential for appreciating the importance of water conservation and protecting our planet's most precious resource.

Frequently Asked Questions (FAQ)

• Why is water called the universal solvent?

  Water is called the universal solvent because it can dissolve more substances than any other solvent. This is due to its polarity, which allows it to interact with a wide range of molecules.

• How does water's high heat capacity help regulate body temperature?

  Water's high heat capacity allows it to absorb a large amount of heat without a significant change in temperature. This helps organisms maintain a stable internal temperature by absorbing heat generated by metabolic processes and releasing it slowly.

• Why does ice float?

  Ice floats because it is less dense than liquid water. When water freezes, it forms crystalline structures that create spaces between the molecules, increasing the volume and decreasing the density.

• How do cohesion and adhesion help plants transport water?

  Cohesion allows water molecules to stick to each other, while adhesion allows water molecules to stick to the walls of the plant's vascular system. These two properties work together to draw water up from the roots to the leaves. This is called capillary action.

• What are the consequences of water pollution on these properties?

  Water pollution can negatively impact water's essential properties. For instance, pollutants can reduce surface tension, alter heat capacity, and affect water density, thereby disrupting aquatic ecosystems and potentially harming human health.

• How is water's surface tension beneficial?

  Water's high surface tension provides habitat for small insects to thrive on its surface and also aids in processes like droplet formation which are crucial for precipitation.

• Can life exist without water?

  As far as we know, all known forms of life depend on water. Its unique properties make it an essential component of biological processes and environmental stability. While other solvents might exist, water's specific attributes are exceptionally suited for life as we understand it.

• Is there anything else that shares water's unique density property?

  Water's density anomaly, where it is less dense as a solid than as a liquid, is relatively rare. Bismuth and gallium are a few other substances that share this property, but water's behavior is particularly significant due to its abundance and role in sustaining life.

• What role does water play in photosynthesis?

  Water is essential in photosynthesis, the process by which plants convert light energy into chemical energy. Water provides the electrons needed for the light-dependent reactions and is a reactant in the overall photosynthetic process.

• How does water help in maintaining the pH balance of living organisms?

  Water helps maintain the pH balance by acting as both an acid and a base, helping to buffer changes in pH levels. This buffering capacity prevents drastic pH fluctuations that can be harmful to cells.