Water on planet earth

Water is found everywhere: in the seas, in the rivers, in the lakes, in the clouds, in the groundwater, in the air, in the animals, in the plants, in the human being. Water is indispensable for life.


On our planet, there is a huge layer on the surface of the earth's crust that is covered with water. We call this layer the hydrosphere, ie the water sphere. Water covers about three quarters of the earth's crust or about 71% of the surface.

Physical states of water

Water is always in one of these physical states: liquid, solid or gaseous.

The water in liquid state It is found in seas, oceans, lakes, rivers, springs and in living things. The water we drink is obtained through rivers, wells, or fountains (from groundwater or groundwater).

Most of the animals' bodies are water. For example, in man, water corresponds to 70% of its weight. In fruits, the amount of water is also large.

The water in solid state It is the ice. In the wild, we find it in many forms such as snow, clouds, hail, frost, icebergs and polar ice caps.

In clouds, small blocks of ice form, but only in cirrus clouds. In the snow, falling ice flakes form and form thick layers. This is because there is a cooling of small drops of water vapor that condense in the air, that is, they pass from gaseous to liquid state.

In the frosts, the water vapor of the atmospheric air turns into small drops of water, the dew. This frozen dew is the frost. It forms on very cold nights, covering the surfaces with ice.

In hail, ice stones form within the storm clouds. Icebergs, which are huge blocks of ice, are formed by the detachment of glaciers that are on the coast to give polar regions. Icebergs float on seas and rivers until they melt into liquid water. The iceberg is an ice mountain where most of it is submerged in the sea.

Gaseous water is found in the form of water vapor that exists in the air, which is formed by evaporation of water from seas, rivers and lakes. In the perspiration and respiration of animals and vegetables there is also water vapor. The evaporated water condenses into small drops. These drops together form the clouds.

To understand how changes in physical states occur, one must understand the composition of substances.

Water is made up of two hydrogen atoms and one oxygen atom. So the chemical formula that represents a water molecule is H2O, indicating that water is formed by two hydrogen atoms and one oxygen.