Question

Ice has an open structure compared to water due to which it floats on water and occupies a greater volume of space. The open structure of ice is due to (1) solid state of ice (2) its low density (3) crystalline nature (4) hydrogen bonding

Short answer

The open structure of ice is due to hydrogen bonding.

Step-by-step solution

Understanding the Reason Ice Floats

The key point in the problem is that ice floats on water and occupies more space due to its structure.

Analyze Each Option

Examine each option to see which one explains why ice has an open structure: (1) Solid state of ice: All solids can have various structures, so this does not explain the specific open structure of ice. (2) Its low density: This is a consequence of its structure, not the cause. (3) Crystalline nature: Crystals can have compact or open structures, thus this is not the cause. (4) Hydrogen bonding: Hydrogen bonds in ice create an open hexagonal structure, making it less dense than water.

Confirming the Correct Answer

The open structure of ice is specifically due to hydrogen bonding, which makes the ice less dense than liquid water and causes it to float. Hence, the correct choice is (4) hydrogen bonding.

Key concepts

ice structure

When water freezes to form ice, its molecules arrange themselves into a hexagonal crystal lattice. This is the 'open structure' mentioned in the exercise.

Due to hydrogen bonding, water molecules are held apart at fixed distances in a way that maximizes the number of hydrogen bonds, forming a pattern with many empty spaces.
This open network is the primary reason why ice occupies more space compared to liquid water. Each oxygen atom in the structure is hydrogen-bonded to four hydrogen atoms: two covalently and two by hydrogen bonds.

This results in a lattice structure that is less dense than water. This unique structure is what imparts ice its lower density, making it float in water.

density comparison

In scientific terms, density is defined as mass per unit volume. Ice has a lower density than liquid water.

Most substances are denser in their solid form than in their liquid form, but water is an exception.
This is due to the hydrogen bonding in ice, which creates a crystalline structure with larger gaps than the semi-random arrangement of molecules in liquid water.

Here’s why ice is less dense:

• In liquid water, molecules are closer together because hydrogen bonds are constantly forming and breaking.
• In ice, each water molecule forms four hydrogen bonds that keep molecules at a fixed distance apart in an expanded structure.


Since the molecules in ice are further apart than in liquid water, ice ends up taking more space, thereby having a lower density. This phenomenon explains why icebergs float on water, as seen in nature.

crystalline nature

Ice is a crystalline solid, meaning it has a well-ordered and repeating atomic structure.

Water crystallizes into an ice lattice when it freezes. This crystalline nature is significantly influenced by hydrogen bonding. The atoms and molecules are organized in a consistent, repeating pattern, which defines the crystalline structure.

Important Points about the Crystalline Nature of Ice:

• The hexagonal lattice formed by hydrogen bonds creates a repeating pattern.
• This pattern includes a lot of empty space, making the structure 'open'.
• The angles in the hexagonal design are consistent, contributing to the rigid, stable nature of ice.


Understanding the crystalline nature of ice helps explain its unique properties, such as floating on water, expansion upon freezing, and relatively lower density compared to liquid water.
Additionally, it's essential to note that this crystalline nature contributes to the distinct properties of ice compared to other solid forms of matter.