Problem 1 - AP Biology Premium Prep 2021

Question

Water is a critical component of life due to its unique structural and chemical properties. Which of the following does NOT describe a way that the exceptional characteristics of water are used in nature to sustain life? A) The high heat capacity of water prevents lakes and streams from rapidly changing temperature and freezing completely solid in the winter. B) The high surface tension and cohesiveness of water facilitates capillary action in plants. C) The low polarity of water prevents dissolution of cells and compounds. D) The high intermolecular forces of water, such as hydrogen bonding, result in a boiling point which exceeds the tolerance of most life on the planet.

Step-by-Step Solution

Answer

Option C is the correct answer. Water is not low in polarity but rather highly polar, allowing it to dissolve a wide variety of substances essential for life.

Step 1: Understand the properties of water

Water has unique properties that make it vital to life. Some of these properties are: - High heat capacity - High surface tension - Cohesiveness - Polarity - High intermolecular forces, such as hydrogen bonding

Step 2: Analyze Option A

Option A states that the high heat capacity of water prevents lakes and streams from rapidly changing temperature and freezing completely solid in the winter. This is a correct statement, as water's high heat capacity allows it to absorb or release large amounts of heat without experiencing significant changes in temperature. This property helps regulate the temperature of the Earth and keeps aquatic life stable.

Step 3: Analyze Option B

Option B says that the high surface tension and cohesiveness of water facilitates capillary action in plants. This is also a correct statement. The strong attraction between water molecules, due to hydrogen bonding, results in a high surface tension. This property allows water to move through tiny spaces, such as in plant roots and capillaries, against the force of gravity via a phenomenon called capillary action.

Step 4: Analyze Option C

Option C states that the low polarity of water prevents dissolution of cells and compounds. This statement is incorrect. Water is actually a highly polar molecule due to the uneven distribution of electrons within the molecule, which allows it to dissolve a wide variety of substances, including salts, proteins, and sugars. Therefore, option C does NOT describe a way that water's characteristics are used to sustain life.

Step 5: Analyze Option D

Option D says that the high intermolecular forces of water, such as hydrogen bonding, result in a boiling point which exceeds the tolerance of most life on the planet. This statement is true, as hydrogen bonding makes it difficult for water molecules to break away and evaporate, thus raising the boiling point of water. However, this boiling point is useful for life, as it ensures that water remains in the liquid state over a wide range of temperatures, which is essential for many biological processes.

Step 6: Choose the correct answer

Since option C is the only statement that does NOT describe a way that the exceptional properties of water are used to sustain life, it is the correct answer. The student should choose Option C as the answer to the question.

Key Concepts

Water Polarity

Water's polarity is one of its most essential characteristics, crucial to sustaining life on Earth. Polarity refers to the distribution of electrical charge around a molecule. In water molecules, the oxygen atom has a slight negative charge, while the hydrogen atoms have slight positive charges. This uneven charge distribution allows water molecules to form hydrogen bonds with each other and with other substances.

This attribute is what makes water an excellent solvent, capable of dissolving a variety of substances necessary for life, such as salts and sugars. These solutions are key to many biological processes, including nutrient transport and chemical reactions in cells. It also influences the structure of the large macro molecules, such as proteins and nucleic acids, that are essential for life processes.

Capillary Action

Capillary action is a phenomenon that can be observed in narrow spaces, such as the tiny vessels in plant roots and stems. It results from the adhesive forces between the water molecules and the walls of the vessels, combined with the cohesive forces within the water itself.

In plants, this effect allows water, along with dissolved nutrients, to travel from the roots up against gravity to reach the leaves and other parts. This upward movement is critical for plant survival and hence, for the sustenance of life on Earth. Without capillary action, plants would not be able to absorb water from the soil or distribute nutrients throughout their tissues.

Water Heat Capacity

Water's high heat capacity is a measure of its ability to absorb and retain heat. This means that water can take in significant amounts of thermal energy without a large increase in temperature. This property stabilizes environments, particularly aquatic ecosystems, by buffering temperature fluctuations.

This thermal stability is critical for organisms, allowing them to thrive even when external temperatures change drastically. It also means that bodies of water like lakes or oceans can provide a stable habitat with a relatively constant temperature, a vital trait for sustaining life throughout the varying seasons.

Hydrogen Bonding

Hydrogen bonding, an intermolecular force, plays a fundamental role in determining water’s unique properties. These bonds form between the slightly positive hydrogen atoms of one water molecule and the slightly negative oxygen atoms of another.

This type of bonding is behind water's high surface tension, its ability to hold heat, and the way it expands when it freezes. Hydrogen bonds are also important inside our bodies, helping to maintain the shapes of proteins and DNA, which are essential for the body's structure and function. Additionally, because hydrogen bonds make it relatively difficult for water molecules to escape as gas, water has a higher boiling point than would be expected for a molecule of its size, contributing to its ability to sustain life in various temperature conditions.