Each substance is characterized by a number of physical and chemical properties on which it can easily be distinguished. At first sight, this knowledge gained within a school course is far from real life. However, we perceive a set of products and materials just on their distinctive properties: to taste, color, smell, density, solubility, hardness. For an example we will consider such recognizable substances as glucose and citric acid.
The underground waters located on a constant aquifer are called ground. They are formed of an atmospheric precipitation, waters of the rivers, lakes, reservoirs and also from inflow of moisture from the surface of the soil. At construction of the hydraulic engineering construction, for example, when digging wells, it is required to determine depth of a proleganiye of ground waters. It is possible to make it in several ways.