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5.2. Water states

Liquid state

Water is usually in a liquid state, since the average temperature of the Earth is about 15 ºC.

Liquid water is part of oceans, seas, rivers, lakes, groundwater, etc.

Water passes from the solid state to the liquid state by fusion, when the temperature exceeds 0 ºC.

The melting point of water is 0 ºC, the temperature at which it changes from a solid state to a liquid state.

Solid state

When the temperature of liquid water drops below 0°C, solidification occurs. Liquid water crystallizes to form ice, which is less dense than liquid water, since when it freezes, the water molecules separate. This is why ice floats on water.

In nature, we can find ice and snow in glaciers and polar ice caps, for example.

Gaseous state

When water absorbs energy, the water molecules separate and become gaseous. The water is then in the form of water vapor.

Evaporation  is the passage of water from the liquid state to the gaseous state, such as when we hang clothes and they dry.

Boiling occurs when the temperature of the water reaches 100 ºC.

In some cases, water can go directly from a gaseous state to a solid state, and this process is called sublimation.

Clarification: Difference between evaporation and boiling.

Changes of water's state

Water, at room temperature, is in a liquid state but, if conditions change, different state changes can occur:

  • Solidification: go from a liquid state to a solid state.
  • Fusion: go from solid state to liquid state.
  • Sublimation: going from a solid state to a gaseous state.
  • Vaporization or vaporization: to go from a liquid state to a gaseous state.
  • Condensation: change from a gaseous state to a liquid.
  • Reverse sublimation: go from gaseous to solid state.

Cambios de estado del agua

Clouds are not water vapor

Although I'm sure you've heard it before, clouds are not water vapor. Clouds are made up of tiny water droplets or ice crystals, or both. Therefore, clouds are water in a liquid state or in a solid state, but not gaseous. In addition, water vapor is transparent and cannot be seen in the atmosphere, but when it condenses, it becomes liquid (or solid) and turns into small droplets that form clouds.