Which Of The Following Is Not True About Water

Water, the lifeblood of our planet, possesses unique properties that sustain ecosystems and enable biological processes. Understanding these properties is crucial for appreciating the significance of water in our lives. Let's explore which of the following statements about water is incorrect, delving into the science behind this remarkable substance.

Water: An Overview

Water (H₂O) is a polar inorganic compound at room temperature, existing as a tasteless and odorless liquid. It's vital for all known forms of life, covering over 71% of the Earth's surface. Water occurs in various states: liquid, solid (ice), and gas (vapor). Its unique properties include its ability to act as a universal solvent, its high surface tension, and its anomalous expansion upon freezing.

Common Misconceptions About Water

Before diving into specific statements, let's address some common misconceptions about water:

Pure water is a good conductor of electricity: Actually, pure water is a poor conductor. It's the presence of ions (dissolved salts and minerals) that makes water conductive.
Water boils at 100°C (212°F) at all altitudes: This is only true at standard atmospheric pressure. At higher altitudes, where the pressure is lower, water boils at a lower temperature.
Water is always a renewable resource: While water is part of a natural cycle, overuse, pollution, and climate change can deplete water resources, making it a scarce commodity in many regions.

Analyzing Statements About Water

Now, let's consider some statements about water and identify the incorrect one. We'll examine each statement in detail, providing scientific explanations to clarify the truth.

Statement 1: Water is a non-polar molecule.

This statement is incorrect. Water is a polar molecule. This polarity arises from the difference in electronegativity between oxygen and hydrogen atoms. Oxygen is more electronegative, meaning it attracts electrons more strongly than hydrogen. This unequal sharing of electrons creates a partial negative charge (δ-) on the oxygen atom and partial positive charges (δ+) on the hydrogen atoms. The bent shape of the water molecule further reinforces its polarity.

Statement 2: Water has a high specific heat capacity.

This statement is correct. Water has an exceptionally high specific heat capacity, meaning it requires a significant amount of energy to raise its temperature. This property is due to the hydrogen bonds between water molecules. These bonds absorb a large amount of heat energy before the water molecules can move faster and increase the temperature.

Statement 3: Water is a universal solvent.

This statement is generally considered correct, though with some caveats. Water's polarity allows it to dissolve a wide range of substances, especially other polar compounds and ionic compounds. This dissolving ability makes it an excellent solvent in biological systems and various industrial processes. However, it does not dissolve all substances, particularly non-polar substances like oils and fats.

Statement 4: Water is less dense in its solid form (ice) than in its liquid form.

This statement is correct. This is an unusual property, as most substances are denser in their solid form. In water, hydrogen bonds create a crystalline structure when it freezes, which forces the molecules to spread out more than in liquid water. This results in ice being less dense and floating on liquid water.

Statement 5: Water has a high surface tension.

This statement is correct. Water's high surface tension is due to the cohesive forces between water molecules, again resulting from hydrogen bonding. The molecules at the surface experience a net inward force, creating a "skin" that resists external forces.

The Correct Answer

Based on the analysis above, the incorrect statement is:

Statement 1: Water is a non-polar molecule.

Scientific Explanation of Water's Properties

To fully understand why the first statement is incorrect and the others are correct, let's delve deeper into the scientific explanations of water's key properties:

Polarity and Hydrogen Bonding

The polarity of water is fundamental to its other properties. The partial positive and negative charges allow water molecules to form hydrogen bonds with each other and with other polar molecules. A hydrogen bond is a relatively weak attraction between a hydrogen atom with a partial positive charge and a highly electronegative atom (like oxygen) with a partial negative charge.

High Specific Heat Capacity

Water's high specific heat capacity (4.184 J/g°C) means it takes 4.184 Joules of energy to raise the temperature of 1 gram of water by 1 degree Celsius. This is significantly higher than many other common substances. The extensive network of hydrogen bonds in water absorbs a considerable amount of heat energy before the water molecules can move faster and increase the temperature. This property helps regulate Earth's climate and protects aquatic organisms from drastic temperature changes.

Universal Solvent

Water's ability to dissolve a wide range of substances is crucial for chemical reactions in living organisms and various industrial processes. When an ionic compound like sodium chloride (NaCl) is placed in water, the polar water molecules surround the ions (Na+ and Cl-). The partial negative charge of oxygen attracts the positive sodium ions, while the partial positive charge of hydrogen attracts the negative chloride ions. This process, called hydration, weakens the ionic bonds and causes the salt to dissolve.

Similarly, water can dissolve other polar molecules like ethanol (C₂H₅OH) because it can form hydrogen bonds with them. However, water cannot dissolve non-polar molecules like oil because there are no significant attractive forces between water and non-polar molecules.

Density Anomaly

The fact that ice is less dense than liquid water is crucial for aquatic life. As water cools, it becomes denser until it reaches 4°C. Below this temperature, water starts to become less dense. When water freezes, the hydrogen bonds form a crystalline lattice structure, which forces the molecules to spread out more than in liquid water. This results in ice being less dense and floating on liquid water.

If ice were denser than liquid water, it would sink to the bottom of lakes and oceans, potentially freezing them solid from the bottom up. This would make it impossible for aquatic life to survive in many regions.

High Surface Tension

Water's high surface tension is also due to the cohesive forces between water molecules. The molecules at the surface experience a net inward force, creating a "skin" that resists external forces. This allows insects to walk on water and is important for capillary action, which helps transport water in plants.

Water's Importance in Biology

Water's unique properties make it essential for life as we know it. Here are some key roles water plays in biological systems:

Solvent: Water is the primary solvent in living organisms, facilitating chemical reactions and transporting nutrients and waste products.
Temperature Regulation: Water's high specific heat capacity helps maintain a stable internal temperature in organisms and regulates Earth's climate.
Transport: Water transports nutrients and waste products in blood, sap, and other biological fluids.
Photosynthesis: Water is a reactant in photosynthesis, the process by which plants convert sunlight into energy.
Structural Support: Water provides turgor pressure in plant cells, which helps maintain their rigidity.
Lubrication: Water lubricates joints and other body parts, reducing friction and allowing for smooth movement.

The Water Cycle

The water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the Earth. This cycle involves several key processes:

Evaporation: The process by which liquid water changes into water vapor and enters the atmosphere.
Transpiration: The process by which water is released from plants into the atmosphere.
Condensation: The process by which water vapor changes into liquid water, forming clouds.
Precipitation: The process by which water falls from clouds to the Earth's surface in the form of rain, snow, sleet, or hail.
Infiltration: The process by which water seeps into the ground and replenishes groundwater supplies.
Runoff: The flow of water over the land surface, eventually reaching rivers, lakes, and oceans.

The water cycle is crucial for distributing water around the globe and maintaining the balance of Earth's ecosystems.

Water Pollution and Conservation

Despite its abundance, water is a precious resource that is increasingly threatened by pollution and overuse. Water pollution can come from various sources, including industrial waste, agricultural runoff, sewage, and plastic waste. Polluted water can harm aquatic life, contaminate drinking water supplies, and spread diseases.

Water conservation is essential for ensuring that future generations have access to clean and safe water. Here are some ways to conserve water:

Reduce Water Consumption: Take shorter showers, fix leaky faucets, and use water-efficient appliances.
Use Water Wisely in the Garden: Water plants in the early morning or late evening to reduce evaporation, use drought-resistant plants, and collect rainwater for irrigation.
Protect Water Sources: Dispose of waste properly, avoid using pesticides and herbicides, and support policies that protect water resources.
Promote Sustainable Agriculture: Use water-efficient irrigation techniques and reduce fertilizer use to minimize agricultural runoff.

Conclusion

Water's unique properties, particularly its polarity, high specific heat capacity, and density anomaly, make it essential for life on Earth. Understanding these properties is crucial for appreciating the significance of water in biological systems, climate regulation, and various industrial processes. The statement "Water is a non-polar molecule" is incorrect, as water's polarity is fundamental to its other characteristics. By conserving water and protecting it from pollution, we can ensure that this precious resource remains available for future generations.

FAQ About Water

Q: Why is water called the universal solvent?

A: Water is called the "universal solvent" because it can dissolve a wide range of substances, especially polar and ionic compounds. Its polarity allows it to interact with and break apart many chemical bonds.

Q: What is the importance of water's high specific heat capacity?

A: Water's high specific heat capacity helps regulate Earth's climate by absorbing and releasing large amounts of heat without significant temperature changes. It also helps organisms maintain a stable internal temperature.

Q: Why does ice float on water?

A: Ice floats on water because it is less dense. When water freezes, the hydrogen bonds form a crystalline structure that forces the molecules to spread out more than in liquid water, reducing its density.

Q: How does water contribute to photosynthesis?

A: Water is a reactant in photosynthesis, the process by which plants convert sunlight into energy. Plants use water, carbon dioxide, and sunlight to produce glucose (sugar) and oxygen.

Q: What are the main stages of the water cycle?

A: The main stages of the water cycle are evaporation, transpiration, condensation, precipitation, infiltration, and runoff.

Q: What are some ways to conserve water at home?

A: Some ways to conserve water at home include taking shorter showers, fixing leaky faucets, using water-efficient appliances, and watering plants wisely.

Q: What are the effects of water pollution?

A: Water pollution can harm aquatic life, contaminate drinking water supplies, spread diseases, and disrupt ecosystems.

Q: Why is water essential for life?

A: Water is essential for life because it acts as a solvent, regulates temperature, transports nutrients and waste, participates in chemical reactions, provides structural support, and lubricates body parts.

Q: What is the chemical formula for water?

A: The chemical formula for water is H₂O, indicating that each water molecule consists of two hydrogen atoms and one oxygen atom.

Q: What is the difference between hard water and soft water?

A: Hard water contains high concentrations of minerals like calcium and magnesium, while soft water contains fewer minerals. Hard water can cause scale buildup in pipes and appliances, while soft water is generally better for cleaning and laundry.