When Water Freezes Does It Expand?

When Water Freezes Does It Expand?

Water is a compound that, in its liquid state, generally occupies all the space it is given. When it freezes, however, it undergoes a physical transition that causes it to expand. This phenomenon is known as thermal expansion, and is an essential factor in the flow of glaciers and other bodies of ice.

Explaining Thermal Expansion

Thermal expansion occurs when an object takes up more space as its temperature decreases. As water freezes, its molecules spread apart, which increases its volume by approximately 9%. Where liquids are more cohesive, the ice crystals are less dense and therefore occupy more space than they did as a liquid. Ice also enjoys this characteristic when heated and melts.

Examples of Thermal Expansion

These properties of water can be witnessed via several phenomena.

  • Ice Dams – As snow accumulates on a surface such as a roof, its thermal expansion can cause it to block runoff from flowing into the gutter system.
  • Cracks in Pavement – During periods of cold weather, thermal expansion can cause water to seep into small cracks that have formed in pavement, widening them and making them bigger.
  • Cracks in Walls – When water enters into small holes and cracks inside walls, thermal expansion can cause this water to expand and put pressure on the surrounding materials. This can lead to more significant and conspicuous damage.


Thermal expansion of water occurs when it freezes and causes it to take up more space than it did when it was a liquid. Thus, thermal expansion is an important factor to consider when dealing with bodies of ice and snow, as it can wreak havoc on structures and materials. It is also an important part of the hydrologic cycle, as it is responsible for the flow of glaciers and other ice masses.