Question

The low density of ice compared to water is due to (1) hydrogen-bonding interactions (2) dipole-dipole interactions (3) dipole-induced dipole interactions (4) induced dipole-induced dipole interactions

Short answer

The low density of ice compared to water is due to hydrogen-bonding interactions.

Step-by-step solution

Identify the Key Concept

The density of ice compared to water is the key concept. It is essential to understand why ice floats on water.

Analyze the Options

Review the given options and understand what each type of interaction means: (1) Hydrogen-bonding interactions (2) Dipole-dipole interactions (3) Dipole-induced dipole interactions (4) Induced dipole-induced dipole interactions

Relate to Physical Properties

Ice is less dense than liquid water. This phenomenon is due to the arrangement of water molecules in the solid-state (ice), where they form a lattice structure that keeps the molecules further apart compared to the liquid state.

Evaluate the Type of Interaction

The structure of ice is held together by hydrogen bonds. These bonds create an open hexagonal structure, leading to a lower density.

Select the Correct Answer

Based on the analysis, the interaction responsible for the lower density of ice compared to water is hydrogen-bonding interactions.

Key concepts

Hydrogen-Bonding

Hydrogen-bonding is a powerful type of dipole-dipole interaction, formed between molecules when a hydrogen atom bonded to a highly electronegative atom like oxygen is attracted to another electronegative atom.
Water molecules exhibit hydrogen-bonding because each water molecule has polar covalent bonds between one oxygen and two hydrogen atoms. The oxygen atom is more electronegative, drawing the shared electrons closer and creating a partial negative charge on the oxygen and partial positive charges on the hydrogens.
This partial charge disparity leads to the attraction between the hydrogen atom of one water molecule and the oxygen atom of another, forming hydrogen bonds. These bonds are what make water and ice compatible with extraordinary properties. The hydrogen-bonding in ice creates a unique structure, which we'll talk about next.

Molecular Interactions

In the context of water and ice, molecular interactions refer mainly to hydrogen-bonding and how these bonds dictate the arrangement and behavior of molecules.
At room temperature, water molecules are in a liquid state, and they are moving constantly, making and breaking hydrogen bonds. This movement allows them to pack closely together, leading to a higher density.
As the temperature drops and water begins to freeze, the movement of molecules slows down. The water molecules start to arrange themselves in a more rigid and fixed structure due to hydrogen-bonding. This is an essential shift because as they form these hydrogen bonds in a more ordered way, they create an open hexagonal lattice.
It's interesting to note that not all molecular interactions are hydrogen bonds. They can also include dipole-dipole, dipole-induced dipole, and London dispersion forces, each involving varying degrees of strength and consequences for molecular behavior.
However, the defining interaction causing the difference in density between ice and water is hydrogen-bonding. The way these bonds arrange the molecules into a lattice brings us to our next topic.

Lattice Structure

A lattice structure refers to a regular, repeating arrangement of atoms or molecules in a material. For ice, this means water molecules are arranged in a specific pattern to form a crystalline structure.
In ice, each water molecule forms hydrogen bonds with four other water molecules, creating an open hexagonal lattice. This pattern is less dense than the structure of liquid water, where the molecules are closer together because they constantly break and remake bonds.
This hexagonal structure of ice contains a lot of empty space compared to liquid water. The molecules are held neatly and orderly, and because they are spread further apart, the overall density of ice is lower. This explains why ice floats on water.
The transition from the less ordered structure of liquid water to the more ordered lattice structure of ice is crucial. Through hydrogen-bonding, the lattice structure becomes key in understanding the density differences and physical properties.