Question

Describe the structure of the common form of ice.

Short answer

Ice Ih has a hexagonal crystal lattice formed by hydrogen bonds, making it less dense than liquid water.

Step-by-step solution

Identify the Common Form of Ice

The most common form of ice is known as Ice Ih. It's the crystalline form that we interact with on Earth's surface.

Describe the Molecular Arrangement

In Ice Ih, water molecules form a hexagonal crystal lattice. Each water molecule is hydrogen bonded to four others, creating a repeating pattern that results in a stable structure.

Explain the Hydrogen Bonding

The oxygen atoms in water molecules are arranged in a tetrahedral shape, with hydrogen bonds forming between the oxygen of one molecule and the hydrogen of another. This leads to the characteristic open hexagonal shape that makes ice less dense than liquid water.

Discuss the Physical Properties

Due to its crystalline structure, Ice Ih is less dense than liquid water, which is why ice floats. This open structure also contributes to ice's ability to fracture into hexagonal plates when broken.

Key concepts

Ice Ih

Ice Ih is the most common form of crystalline ice that we encounter in everyday life. It's the version of ice found when water freezes under normal atmospheric conditions on Earth. This structure is also known as "hexagonal ice" because of its unique arrangement of molecules. The "Ih" stands for "ice-one" (h for hexagonal), and it is one of seventeen different crystalline phases of ice. Unlike other forms, Ice Ih has a stable structure that is predominantly found in snowflakes and ice cubes. It is well-known for its less dense nature compared to liquid water.

This lower density results from its crystalline arrangement, which allows it to float on water. The phenomenon that Ice Ih floats is crucial for aquatic life, as it insulates water bodies during cold temperatures, preventing them from freezing solid.

Hydrogen Bonding

Hydrogen bonding is key to the unique properties of Ice Ih. In water molecules, each oxygen atom is bonded to two hydrogen atoms via polar covalent bonds. This means that the oxygen, being more electronegative, pulls the electrons towards itself, creating a slight negative charge on the oxygen and a slight positive charge on the hydrogens. The result is a polar molecule.

In Ice Ih, each water molecule forms hydrogen bonds with four neighboring molecules, leading to a tetrahedral structure. These bonds occur when the hydrogen atom of one water molecule experiences an attraction to the oxygen atom of another water molecule.

This specific hydrogen bonding is responsible for the open hexagonal structure of Ice Ih. It also contributes to ice being less dense than liquid water because it keeps the molecules apart, forming an organized lattice structure rather than allowing them to pack closely together.

Hexagonal Crystal Lattice

The hexagonal crystal lattice of Ice Ih is fundamental to its structure and properties. Derived from hydrogen bonding, this lattice consists of repeating hexagonal patterns formed by the connection of water molecules.

Because of the tetrahedral arrangement of these hydrogen bonds, each water molecule connects to four others: two hydrogen atoms form bonds with the oxygen of neighboring molecules, and this pattern repeats. This creates a spacious and open structure.

The hexagonal crystal lattice is responsible for several unique characteristics of ice:

• It allows ice to float on liquid water due to lower density.
• It gives ice a characteristic cleavage into flat planes or hexagonal plates.
• The open framework is why ice has a high degree of brittleness compared to more tightly packed structures.

Overall, this specific lattice structure leads to the distinctive properties of Ice Ih that are observed in nature.