Question

Which of the following properties of water is not due to hydrogen bonding between water molecules? a. Water prevents large temperature changes. b. Ice floats on water. c. Water is a solvent for polar molecules and ionic compounds. d. Water flows and fills spaces because it is cohesive.

Short answer

The property of water that is not due to hydrogen bonding between water molecules is: d. Water flows and fills spaces because it is cohesive. This property is more about the mobility of water molecules, their kinetic energy, and their spherical shape, rather than hydrogen bonding.

Step-by-step solution

List the properties of water mentioned in the options

The exercise lists four properties of water: a. Water prevents large temperature changes. b. Ice floats on water. c. Water is a solvent for polar molecules and ionic compounds. d. Water flows and fills spaces because it is cohesive.

Analyze the properties of water related to hydrogen bonding

a. Water prevents large temperature changes: This property is due to the high specific heat capacity of water, which is a result of the hydrogen bonds between water molecules. When heat is added to the water, much of it is absorbed by breaking these bonds rather than increasing the kinetic energy of the water molecules, which would increase the temperature. b. Ice floats on water: This is also a result of hydrogen bonding between water molecules. In the solid ice state, these bonds form a hexagonal structure, creating an open network that is less dense than the liquid water. This causes ice to be less dense than water, making it float. c. Water is a solvent for polar molecules and ionic compounds: Hydrogen bonding allows water to dissolve polar molecules and ionic compounds. Since water is a polar molecule, the positive and negative ends of the water molecule are attracted to the respective negative and positive ends of other polar molecules or ions. This causes the solute to dissolve.

Identify the property that is not due to hydrogen bonding

d. Water flows and fills spaces because it is cohesive: Although water is cohesive due to hydrogen bonding, the flow of water and its ability to fill spaces are more about the mobility of water molecules, which is a result of their kinetic energy and their spherical shape, rather than hydrogen bonding. So the correct answer is: d. Water flows and fills spaces because it is cohesive.

Key concepts

Hydrogen Bonding

When we talk about the remarkable traits of water, the term hydrogen bonding frequently pops up. This is because hydrogen bonds are the superstars behind water's unique properties. To understand how it works, picture each water molecule as a tiny magnet with a positive and a negative end. Hydrogen bonding occurs when the positive end (hydrogen) of one water molecule is attracted to the negative end (oxygen) of another. This attraction is much weaker than a chemical bond but stronger than most other intermolecular forces. It's like a gentle handshake between molecules.

Hydrogen bonding imparts water with many of its life-supporting features: it explains why water has a high boiling point compared to other similar molecules, why ice is less dense than liquid water—enabling it to float—and how water can climb up plant roots and stems through capillary action. These special connections even influence how biological molecules like DNA and proteins maintain their structure and function. Without hydrogen bonds, water wouldn't be the life-sustaining substance we know.

Specific Heat Capacity

Ever wonder why water is rather slow to heat up or cool down? This behavior is due to water's high specific heat capacity. The specific heat capacity of a substance is basically the amount of heat needed to raise the temperature of one gram of that substance by one degree Celsius. For water, this value is pretty high, which means it takes a lot of heat to increase its temperature. But why is that?

Role of Hydrogen Bonding

Here's where hydrogen bonding plays a critical role. When heat is added to water, a big portion of that heat energy goes into breaking the hydrogen bonds between water molecules rather than just making the molecules move faster (which would raise the temperature). Similarly, when water cools and releases heat, it's also forming those hydrogen bonds, which releases energy. This property of water moderates climates, stabilizes ocean temperatures, and allows for a much more habitable planet—making beach days and ecosystem diversity possible.

Solvent Characteristics

If Earth's nickname is 'the blue planet,' then water deserves the title of 'universal solvent.' Water is famously known for its ability to dissolve a plethora of substances, which is why it's often found as the main ingredient in solutions, ranging from our blood to the oceans. The solvent characteristics of water can be credited once again to, you guessed it, hydrogen bonding. Water's polar nature means it has partial positive charges and partial negative charges due to the uneven distribution of electrons caused by the oxygen and hydrogen atoms.

The Power to Dissolve

These charges are not just for show; they enable water to interact with various solutes. Positive ends of water molecules attract negative ions, and the negative ends attract positive ones, surrounding them and pulling them into solution. This capacity turns water into a transport medium, carrying nutrients in bodies, facilitating chemical reactions in cells, and moving substances through ecosystems. Additionally, the solvent power of water is crucial for washing away waste and pollution, both in natural environments and in our daily lives.