Skip Navigation
Search

What Is the Water Cycle?

Author(s): Nancy P. Moreno, PhD, Barbara Z. Tharp, MS, and Judith Dresden, MS.

The Science of the Water Cycle

Water is unique because it can exist naturally on Earth as all three states of matter. This is possible because water has both a high boiling point (100°C or 212°F) and a low freezing point (0°C or 32°F). Therefore, it can be found naturally as a solid (ice and snow), a liquid (liquid water) and a gas (steam or water vapor) at any time on our planet. 

Fortunately, liquid water changes temperature very slowly. This characteristic of water helps animals to maintain the temperatures of their bodies. It also keeps larger areas of water from warming or cooling rapidly, which helps to regulate Earth’s climate. Another unique property of water that it expands when frozen. Unlike most substances, water takes up more space as a solid because the molecules in ice crystals are farther apart than those in liquid water. Because it is less dense, ice floats on top of liquid water, allowing many organisms to survive beneath the ice, even in subfreezing temperatures.


Funded by the following grant(s)

National Institute of Environmental Health Sciences, NIH

National Institute of Environmental Health Sciences, NIH

The Environment as a Context for Opportunities in Schools
Grant Numbers: 5R25ES010698, R25ES06932


Houston Endowment Inc.

Houston Endowment Inc.

Foundations for the Future: Capitalizing on Technology to Promote Equity, Access and Quality in Elementary Science Education