The States of Water: Solid, Liquid, or Vapor

A D

16th Mar 2019

Water is a special substance because it exists naturally on Earth in abundance in all three states of matter. When you drink a bottle of water, it's in the liquid form. When you see snowflakes falling, it's in the solid state. In the gaseous state, it exists as water vapor, which is everywhere but invisible. And water can move through all of these states in a process known as the water cycle.

Water as a Solid

Water exists as ice, frost, and snow in the solid state. The freezing point of water is measured at 32º Fahrenheit or 0º Celsius. As the temperature falls, the water molecules move closer together until around 4º Celsius, when water reaches its peak density. Below 4º Celsius, a strange thing happens: The water molecules begin to separate, making the ice less dense than liquid water. This phenomenon explains why ice floats in water. At freezing point, liquid water hardens, gaining sufficient density to become a solid. In the solid state, water has a fixed volume and it holds its shape. When the temperature rises, a block of ice will turn into liquid or water vapor. The density of frozen water is approximately 90 percent of that of liquid water, so only about 10 percent of the ice floats above the water surface.

Water as a Liquid

In the liquid form, water exist in seas, rivers, ponds, and rain. Most living things will perish without liquid water: Plants, animals, and humans need water in its liquid form to survive. Liquid water exists at room temperature, which is between the freezing and boiling points, and it has a fixed volume but no fixed shape. Strangely, the water molecules in liquids are more densely packed than those in the solid or vapor state. One water molecule is made up of two atoms of hydrogen and one atom of oxygen. The oxygen atom has a negative charge, and the hydrogen atoms have a positive charge. The polarity of the atoms produces a slight force between them known as a hydrogen bond. Water molecules can form this bond just as easily as it's broken.

Water as a Gas

Liquid water becomes water vapor at the boiling point, which is 212º Fahrenheit or 100º Celsius. As the temperature rises, the water molecules move faster, weakening their hydrogen bonds. At the boiling point, the force of the speed of the water molecules' movement exceeds the strength of the bonds, so they are separated. The density of water molecules in water vapor is the lowest among the three states. As a gas, water has no fixed shape or volume: It takes the shape and volume of its container. While you can't see water vapor, you can certainly feel it. In humid places, there's plenty of water vapor in the atmosphere, so you may feel that the air is 'sticky.'

The Water Cycle

The water cycle consists of four distinct stages. In the evaporation stage, water in the oceans, rivers, and lakes is heated up by the sun, turning liquid water into gas. The lighter water vapor rises, but it begins to get heavier higher up in the atmosphere as the temperature drops. In the condensation stage, the water vapor cools down and transforms back into liquid, resulting in the formation of clouds. When the water droplets in a cloud become dense enough, they fall as snow or rain, depending on the temperature. This is the precipitation stage. In the collection stage, water flows into bodies of water like oceans, rivers, and lakes. Then, the water cycle begins all over again.

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