Problem 6 - Biology Concepts and Applications

Question

Liquid water shows ___. a. polarity b. hydrogen-bonding capacity c. notable heat resistance d. cohesion e. b through d f. all of the above

Step-by-Step Solution

Answer

Liquid water shows all of the above characteristics, so the answer is f.

Step 1: Identify Key Characteristics of Liquid Water

Liquid water is known to possess several qualities: polarity, due to the difference in electronegativity between hydrogen and oxygen atoms; the ability to form hydrogen bonds, as it can both accept and donate hydrogen bonds; resistance to heat, due to its high specific heat capacity; and cohesion, due to the attraction between water molecules.

Step 2: Evaluate Each Option

Analyze each option: - a (polarity): Water is polar. - b (hydrogen-bonding capacity): Water can form hydrogen bonds. - c (notable heat resistance): Water has a high specific heat capacity, indicating resistance to temperature changes. - d (cohesion): Water molecules are cohesive. - e (b through d): Encompasses hydrogen-bonding capacity, heat resistance, and cohesion. - f (all of the above): Includes polarity and options b through d.

Step 3: Determine the Correct Choice

Since liquid water displays all the identified characteristics—polarity, hydrogen-bonding capacity, heat resistance, and cohesion—the most accurate choice is option f (all of the above).

Key Concepts

Polarity

Water's polarity is a cornerstone of its unique behaviors and interactions. The polar nature is a result of the difference in electronegativity between the oxygen and hydrogen atoms.

• Oxygen is more electronegative, meaning it attracts electrons more strongly than hydrogen.
• This creates a partial negative charge near the oxygen atom and a partial positive charge near the hydrogen atoms, establishing a dipole moment.

This polarity allows water to interact strongly with other polar molecules and ions. It can dissolve many substances, earning water the nickname "universal solvent." Water's ability to dissolve salts, sugars, acids, and gases is crucial for biological processes in living organisms.

Hydrogen Bonding

Hydrogen bonding is a special type of attraction between molecules that occurs in water. Each water molecule can form up to four hydrogen bonds with surrounding molecules. This capacity gives water its very high boiling point relative to its molecular weight.

• Hydrogen bonds occur because the positive hydrogen atoms of one water molecule attract the negative oxygen atoms of another.
• This network of hydrogen bonds creates a unique structure and gives water some of its important properties.

Hydrogen bonding is responsible for water's high surface tension and its ability to climb in narrow tubes due to capillary action. This is why plants can transport water from roots to leaves.

Heat Resistance

Water's heat resistance, or specific heat capacity, is notably high. This means it can absorb or release significant amounts of heat with minimal temperature change. This property is essential for both the environment and living organisms.

• The high specific heat is due to hydrogen bonding, which requires more energy to break before temperature changes occur.
• This allows water to stabilize temperatures in organisms and environments.

For instance, ocean temperatures stay relatively stable, moderating global climate. Similarly, our bodies use water to help stabilize internal temperatures, protecting organs during extreme conditions.

Cohesion

Cohesion refers to the attractive force between like molecules, specifically water molecules in this case. This property is due in large part to hydrogen bonding.

• Water molecules stick to each other, creating surface tension.
• This is why small insects can walk on water’s surface, relying on the resistance created by cohesive forces.

Cohesion also plays a critical role in the transportation of water and nutrients in plants. It helps in pulling water up through the roots and stems, reaching even the highest leaves of tall trees. Understanding cohesion is key to appreciating the delicate balance maintained within ecosystems.