Properties Of Water Worksheet Answers

The Amazing Properties of Water: A Comprehensive Worksheet and Answer Key

Water. It's the most abundant substance on Earth, crucial for all known life, and possesses unique properties that make it unlike any other molecule. Understanding these properties is key to comprehending the complexities of our world, from the weather patterns to the intricate workings of our cells. This comprehensive guide serves as both a detailed explanation of water's remarkable properties and a complete answer key for a worksheet designed to test your understanding.

Introduction: Why Water is Special

Water, chemically represented as H₂O, is a seemingly simple molecule, yet its properties are anything but simple. Its unique structure, with its slightly positive hydrogen atoms and slightly negative oxygen atom, leads to several remarkable characteristics that are essential for life as we know it. This worksheet and answer key will explore these properties in detail, including cohesion, adhesion, high specific heat capacity, high heat of vaporization, density anomaly, and its role as a universal solvent. Understanding these properties is crucial for comprehending various biological and environmental processes.

Worksheet: Properties of Water

(Instructions: Answer the following questions to the best of your ability. Refer to the accompanying text for assistance.)

Section 1: Polarity and Hydrogen Bonding

1. Explain the concept of polarity in water molecules. Why is water considered a polar molecule?
2. Describe hydrogen bonding. How does it occur in water, and what are its implications for water's properties?
3. Draw a diagram showing the hydrogen bonding between four water molecules.

Section 2: Cohesion and Adhesion

4. Define cohesion and adhesion. How do these properties relate to water's behavior in plants?
5. Explain the role of surface tension in water. What causes surface tension?
6. Describe capillary action. Give an example of capillary action in nature.

Section 3: Specific Heat and Heat of Vaporization

7. Define specific heat capacity. Why does water have a high specific heat capacity?
8. Explain the significance of water's high specific heat capacity for climate regulation and for living organisms.
9. What is the heat of vaporization? Why is water's heat of vaporization high?
10. Explain how sweating helps cool the body down.

Section 4: Density Anomaly

11. Describe the density anomaly of water. What is unique about the density of ice compared to liquid water?
12. Explain the importance of the density anomaly of water for aquatic life.

Section 5: Universal Solvent

13. Why is water considered a universal solvent?
14. Give examples of substances that dissolve readily in water and explain why.
15. Give examples of substances that do not dissolve readily in water and explain why.

Answer Key: Properties of Water

Section 1: Polarity and Hydrogen Bonding

1. Water is a polar molecule because the oxygen atom is more electronegative than the hydrogen atoms. This means the oxygen atom attracts the shared electrons more strongly, creating a slightly negative charge (δ-) on the oxygen and slightly positive charges (δ+) on the hydrogens. This unequal distribution of charge creates a dipole moment.
2. Hydrogen bonding is a special type of dipole-dipole attraction between molecules, where a hydrogen atom bonded to a highly electronegative atom (like oxygen in water) is attracted to another electronegative atom in a nearby molecule. In water, the slightly positive hydrogen atom of one molecule is attracted to the slightly negative oxygen atom of another molecule. This creates strong intermolecular forces, significantly impacting water's properties.
3. (Diagram should show four water molecules arranged tetrahedrally, with dashed lines representing hydrogen bonds between the slightly positive hydrogen of one molecule and the slightly negative oxygen of another.)

Section 2: Cohesion and Adhesion

4. Cohesion is the attraction between molecules of the same substance (water molecules sticking to each other). Adhesion is the attraction between molecules of different substances (water molecules sticking to other surfaces). In plants, cohesion allows water molecules to form a continuous column in the xylem, while adhesion helps the water column stick to the xylem walls, enabling water transport against gravity.
5. Surface tension is the tendency of liquid surfaces to shrink into the minimum surface area possible. It's caused by the cohesive forces between water molecules at the surface, which are stronger than the forces between surface molecules and air molecules.
6. Capillary action is the movement of water up a narrow tube against gravity. It's due to the combined effects of adhesion (water adhering to the tube walls) and cohesion (water molecules pulling each other upwards). Examples include water rising in thin plant stems or the movement of water in a straw.

Section 3: Specific Heat and Heat of Vaporization

7. Specific heat capacity is the amount of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius. Water has a high specific heat capacity because of its strong hydrogen bonds. A significant amount of energy is needed to break these bonds and increase the kinetic energy of the water molecules, leading to a slower temperature increase.
8. Water's high specific heat capacity helps regulate Earth's climate by moderating temperature fluctuations. Large bodies of water absorb and release large amounts of heat with minimal temperature change, preventing extreme temperature swings in coastal areas. In living organisms, it helps maintain a stable internal temperature.
9. Heat of vaporization is the amount of heat required to convert 1 gram of a liquid into a gas at its boiling point. Water's high heat of vaporization is also due to its strong hydrogen bonds, requiring a substantial amount of energy to overcome the intermolecular attractions and transition to the gaseous phase.
10. Sweating cools the body down because the evaporation of sweat from the skin absorbs a significant amount of heat energy. This heat is taken from the body, lowering the body's temperature. The high heat of vaporization of water makes sweating an effective cooling mechanism.

Section 4: Density Anomaly

11. The density anomaly of water refers to the fact that ice is less dense than liquid water. This is unusual, as most substances become denser when they freeze. The unique crystal structure of ice, with its open hexagonal arrangement, creates more space between water molecules than in liquid water, leading to lower density.
12. The density anomaly of water is crucial for aquatic life. Because ice floats, it insulates the water below, preventing it from freezing solid and allowing aquatic organisms to survive in winter.

Section 5: Universal Solvent

13. Water is considered a universal solvent because its polar nature allows it to dissolve a wide range of ionic and polar substances. The slightly positive and negative charges of the water molecule can interact with and surround charged particles (ions) or polar molecules, pulling them apart and keeping them in solution.
14. Substances like salt (NaCl) and sugar (sucrose) dissolve readily in water because their ionic or polar nature allows them to interact with the polar water molecules. The positive ions are attracted to the negative oxygen of water, and the negative ions are attracted to the positive hydrogens.
15. Substances like oil and fats do not dissolve readily in water because they are nonpolar. They lack charged regions or significant dipole moments, and therefore cannot interact effectively with the polar water molecules. The strong cohesive forces between water molecules prevent nonpolar molecules from entering the water structure.

Conclusion: The Importance of Understanding Water's Properties

This detailed exploration of water's properties highlights its remarkable and essential role in our world and in the biological systems that thrive upon it. From its ability to moderate temperature to its role as a universal solvent, water's unique characteristics are fundamental to the very existence of life. This worksheet and answer key serve as a valuable resource for understanding these vital properties and appreciating the incredible complexity of this seemingly simple molecule. Further research into the intricacies of water's behavior can lead to a deeper understanding of various scientific disciplines, from biology and chemistry to environmental science and geology. The importance of water extends far beyond its simple chemical formula; it is a substance that underpins the fabric of life itself.