Have you ever wondered why ice cubes float in your drink instead of sinking, or why giant chunks of ice, known as icebergs, stay afloat in the ocean? This floating phenomenon isn’t just a fascinating quirk of nature, but an essential feature that helps sustain life on Earth.

Water molecules (Hâ‚‚O) are made up of two hydrogen atoms and one oxygen atom. Each water molecule has a bent shape and is polar, meaning that the oxygen end is slightly negative while the hydrogen ends are slightly positive. This polarity allows water molecules to form hydrogen bonds, a type of intermolecular forces between molecules. In liquid water, these bonds are constantly forming and breaking as the molecules move freely.

As the temperature drops, water molecules lose energy and move more slowly. When water freezes, the molecules arrange themselves into a crystal lattice, a beautiful, orderly structure held together by hydrogen bonds. This lattice keeps the water molecules farther apart, forming an open hexagonal arrangement that traps air spaces.  As a result, ice occupies about 9% more volume than the same amount of liquid water. This airy, honeycomb-like arrangement makes ice less dense, allowing it to float, whether it’s an ice cube in your drink or a massive iceberg in the ocean. This unique property of water is crucial for life on our planet.

When lakes, rivers, and ponds freeze in winter, the ice forms on the surface first and acts like an insulating blanket. The water beneath remains liquid, providing a safe habitat for fish and aquatic plants to survive the cold season. If ice were denser than water and sank, bodies of water would freeze solid from the bottom up, making life in cold climates nearly impossible. A similar principle can be observed in frost weathering process. When water seeps into crack rocks and freezes overnight, it expands and widening the gaps. Over time, this repeated freezing and thawing process can break down rocks into smaller pieces, shaping the entire landscapes. In colder countries, this process can also damage roads and concrete structures, leading to potholes and cracks.

Figure 1. Illustration of the unique behaviour of water during freezing that gives rise to various phenomena.

From floating icebergs that regulate ocean temperatures to tiny ice crystals that split mountain rocks apart, these unique behaviours of water when it freezes plays a vital role in maintaining ecosystems and shaping the planet. Something as simple as an ice cube floating in your glass is a small reminder of one of nature’s most remarkable designs.

Prepared by,

Intan Diana Mat Azmi, Ph.D

Chemistry Division

Centre for Foundation Studies in Science of Universiti Putra Malaysia

Tarikh Input: 10/11/2025 | Kemaskini: 10/11/2025 | hasniah