Water is a solvent
In the environment it is very difficult to find pure water because of the ease with which other substances mix with it. Even rainwater, for example, when falling, brings air impurities dissolved in it.
One of the important properties of water is the ability to dissolve other substances. Water is considered universal solvent, because it is very abundant on earth and is capable of dissolving much of the known substances.
If we notice color, smell or taste in water, it is due to substances (liquids, solids or gases) present in it, dissolved or not.
Substances that dissolve in others (eg salt) are called solute. The substance that is capable of dissolving others, such as water, is called a solvent. The association of solute with solvent is a solution.
The property that water has to act as a solvent is fundamental to life. In the blood, for example, various substances - such as minerals, vitamins, sugars, among others - are transported dissolved in water.
Percentage of water in some organs of the human body.
In plants, mineral salts dissolved in water are carried from roots to leaves, just as plant food (sugar) is also transported dissolved in water to all parts of this organism.
Within living organisms, there are innumerable indispensable chemical reactions to life, such as those occurring in digestion. Most of these chemical reactions in the body only happen if the chemicals are dissolved in water.
Water as a thermal regulator
Water has the ability to absorb and conserve heat. During the day, the water absorbs some of the sun's heat and conserves it until the night. When the sun is illuminating the other side of the planet, this water is already beginning to return the absorbed heat to the environment.
It thus functions as a thermal regulator. Therefore, in cities near the coast, the difference in temperature is small between day and night. In cities far from the coast, this temperature difference is much larger.
It is this property of water that makes sweating an important mechanism in maintaining the body temperature of some animals.
When the day is very hot, we sweat more. By evaporating the eliminated sweat, we release excess heat in the body. This also occurs when we run, dance or practice other physical exercises.