Water is the substance that exists naturally on Earth in all three classical states of matter: solid, liquid, and gas.
Water can exist as a solid in the form of ice, which occurs at temperatures below 0 degrees Celsius (32 degrees Fahrenheit). In this state, water molecules are arranged in a regular pattern, forming a crystalline structure.
At temperatures above 0 degrees Celsius but below 100 degrees Celsius (212 degrees Fahrenheit), water exists as a liquid. In this state, the water molecules have enough energy to move around and flow, but they are still closely packed together.
When water is heated to temperatures above 100 degrees Celsius (212 degrees Fahrenheit), it undergoes a phase change and turns into a gas known as water vapor. In the gaseous state, water molecules have high energy and are free to move around independently.
Water's ability to exist in all three states is essential for various natural processes on Earth, such as the water cycle, where water evaporates from bodies of water, forms clouds, and eventually condenses and falls back to the Earth as precipitation.