Showing posts with label October 2008. Show all posts
Showing posts with label October 2008. Show all posts
Did you know?
By Bianca Roxana Masgras , XI B class
“Vasile Alecsandri” High School, Galati, Romania
“Vasile Alecsandri” High School, Galati, Romania
- a person drinks during a lifetime 60.000L of water ???
- human beings die if they lose more than 20% out of the normal water content of their body ???
- the wettest place on earth is Cherrapunji from India, where rainfalls reach a12.040 mm ???
- ¾ out of the resources of sweet water are frozen in glaciers and ice calottes ???
What’s water?
By Masgras Bianca Roxana, XI B class “Vasile Alecsandri” High School, Galati, Romania
The water’s pressure
When we stay in a pool and the water is near our neck, our hands are moving because water hitches them.
Why do boats float?
Boats float because they push water. If they crow out more water, water pushes them.
Sea and ocean
Hot water and cold water
Water blanket three parts from the Earth area. At Equator, sea are hot, in South-Pole they are cold. Currents can concur at the warming up or the water refrigerating. Currents are parts of water which can move and form big water rings. They are the Earth rotation aftermath.
Why are sea and ocean salt?
Rivers and raining water wash saline minerals form the ground. Some animal use salt for their conches. Small seas are the most salt. The Dead Sea from Israel is so salt, that fish can’t live there. If sea and ocean deplete, from the salt we can build round the Equator a bench high 282 km and sluggish 1, 5 km.
What are winds?
Water seems to get forward, but really it goes up and down. Winds can pervade hundreds of kilometers. They are high and their copings are bowling when it arrives ashore. Earthquakes and submarine eructation cause big winds, with high about 10 meters.
Tides
Water stands up and retires twice a day. These phenomenons are named high tide and low tide and are caused by the Moon and the sun attraction. The Moon surrounds the Earth, it has an attraction effect about the sea and ocean’s water, which stands up where’s the Moon (high tide) and retires on the other side of the Earth (low tide).
• Water is a liquid. It doesn’t have its own form; it takes the container’s form.
• When we pour water in a glass, water takes the glass form.
• When we spill water on the floor, it spreads because nothing keeps it in a certain form.
Where does water disappear?
Water from mere disappear when is hot. It transforms in small drops and we don’t see it. These drops, named water gas, stand up in air. The water alteration in water gas and them standing up in air is named evaporation. Air is full of water gas because the Sun’s fieriness makes water from sea and ocean evaporates. When the water gas are standing up, they meet the cold air form high and transform in drops of rain, which accumulate in clouds. The rain drops fall on the ground. The water gas transformation in water is named condensation.• When we pour water in a glass, water takes the glass form.
• When we spill water on the floor, it spreads because nothing keeps it in a certain form.
Where does water disappear?
The water’s pressure
When we stay in a pool and the water is near our neck, our hands are moving because water hitches them.
Why do boats float?
Boats float because they push water. If they crow out more water, water pushes them.
Hot water and cold water
Water blanket three parts from the Earth area. At Equator, sea are hot, in South-Pole they are cold. Currents can concur at the warming up or the water refrigerating. Currents are parts of water which can move and form big water rings. They are the Earth rotation aftermath.
Why are sea and ocean salt?
Rivers and raining water wash saline minerals form the ground. Some animal use salt for their conches. Small seas are the most salt. The Dead Sea from Israel is so salt, that fish can’t live there. If sea and ocean deplete, from the salt we can build round the Equator a bench high 282 km and sluggish 1, 5 km.
What are winds?
Water seems to get forward, but really it goes up and down. Winds can pervade hundreds of kilometers. They are high and their copings are bowling when it arrives ashore. Earthquakes and submarine eructation cause big winds, with high about 10 meters.
Tides
Water stands up and retires twice a day. These phenomenons are named high tide and low tide and are caused by the Moon and the sun attraction. The Moon surrounds the Earth, it has an attraction effect about the sea and ocean’s water, which stands up where’s the Moon (high tide) and retires on the other side of the Earth (low tide).
The molecule of water
By Sara Martins, 11º Zi
Escola Secundária de Loulé, Portugal
Water molecule has an angular geometry due to the existence of two lone pairs of electrons around de oxygen atom.
In molecules electrons exist in pairs. Some of these pairs are used ion bonding and the others are lone pairs around atoms.
The pairs of electrons have a repulsive effect over each other because they have the same charge. To minimize these repulsions one should expect that the four pairs of electrons around oxygen would have the maximum separation between themselves, which should be achieved by having a tetrahedral distribution around the central atom. This would mean that the angles between them are of 109.5º.
But this is not what happens. The repulsions of the lone pairs over the bond electrons are bigger than the repulsions between the bonding pairs. This gives the distribution of the electron pairs around oxygen the geometry of a distorted tetrahedron which has the consequence that the angle between chemical bonds is 104.5º.
Waters bond length is 95.7 pm (1 pm = 1 x 10-12 m).
Oxygen is more electronegative than hydrogen. This means that the electrons of the chemical bonds will be in average closer to the oxygen atom. As a consequence of the unequal share of the electron pairs there is a zone with negative charge density around oxygen and one can say that the region around the hydrogen atoms has a positive charge density. The fact that the molecule is angular allows us to think that it has two "sides": one with the hydrogen atoms and one with the oxygen atom. From this point of view waters molecule is an electric dipole with the negative pole closer to the oxygen atom and the positive pole closer to the hydrogen atoms.
Due to waters molecule polarity this substance has important physical properties as the capability of solving polar or ionic substances because it establishes strong intermolecular interaction with them.
On the other hand it cannot solve non polar substances because the intermolecular interactions with the molecules of these substances are much weaker than the interactions that water molecules establish with each other.
Escola Secundária de Loulé, Portugal
Water molecule has an angular geometry due to the existence of two lone pairs of electrons around de oxygen atom.
The pairs of electrons have a repulsive effect over each other because they have the same charge. To minimize these repulsions one should expect that the four pairs of electrons around oxygen would have the maximum separation between themselves, which should be achieved by having a tetrahedral distribution around the central atom. This would mean that the angles between them are of 109.5º.
But this is not what happens. The repulsions of the lone pairs over the bond electrons are bigger than the repulsions between the bonding pairs. This gives the distribution of the electron pairs around oxygen the geometry of a distorted tetrahedron which has the consequence that the angle between chemical bonds is 104.5º.
Waters bond length is 95.7 pm (1 pm = 1 x 10-12 m).
Oxygen is more electronegative than hydrogen. This means that the electrons of the chemical bonds will be in average closer to the oxygen atom. As a consequence of the unequal share of the electron pairs there is a zone with negative charge density around oxygen and one can say that the region around the hydrogen atoms has a positive charge density. The fact that the molecule is angular allows us to think that it has two "sides": one with the hydrogen atoms and one with the oxygen atom. From this point of view waters molecule is an electric dipole with the negative pole closer to the oxygen atom and the positive pole closer to the hydrogen atoms.
Due to waters molecule polarity this substance has important physical properties as the capability of solving polar or ionic substances because it establishes strong intermolecular interaction with them.
On the other hand it cannot solve non polar substances because the intermolecular interactions with the molecules of these substances are much weaker than the interactions that water molecules establish with each other.
Water
By Violeta Geru, XI B class
“Vasile Alecsandri” High School, Galati, Romania
INTRODUCTION
Water is one of the predominant component of Earth, with a major role in the survival of organisms.
The seas and oceans ocuppy 71% of the globe’s surface and in most cells water is approximately 60% of their weight. She is the principal solvent and the dispersion environment of different substances. Water helps at the substances transport and numerous chemical reactions. In the same time, she is present in the human body in 60%, and man’s daily consumption is 2,5 l in food and liquids.
GENERAL CHARACTERISATION
Molecular formula: H2O.
Melting point: 0 ºC.
Boiling point: 100 ºC.
Maxim density: 1g / cm3.
Density at 25 ºC: 0,99701g / cm3.
NATURAL STATE
In solid state (ice) she has almost a double number of hydrogen links than in the liquid state. Here are two hypothetical networks of water molecules. Dark blue represents oxygen and red hydrogen. Magenta bonds are bonds within each water molecule, light blue bonds are hydrogen bonds between molecules. Some bonds extend up or down out of the plane of the diagram. Hydrogen-Oxygen bonds extending up are shown by a hydrogen atom superimposed on the oxygen. If a water molecule is show with only one bond, the other extends down. Hydrogen bonds in and out of the plane of the diagram are not shown.
In all ice structures known, hydrogen is in two-fold coordination with oxygen, and oxygen in fourfold (tetrahedral) coordination with hydrogen. This geometry is dictated by the bond structure of oxygen, not by considerations of ionic radius. In size terms the hydrogen is a mere bump on the oxygen atom. In all known forms of ice, the water molecules retain their identities as distinct molecules and bond to other molecules by hydrogen bonding
Ice is used as a refrigerating agent because it takes more energy to melt it than most other substances, due to strong hydrogen bonds. Melting ice remains at a constant 0°C (32F).
Because ice is less dense than water at 0°C (32F) a mass of ice occupies 9% more volume than an equal mass of water. This is why when water in pipes freezes it can cause the pipes to burst. Another important point about ice being less dense than water is that it floats.
In the following figures there are represented microscopic images of some snow crystals:
PHYSICAL PROPERTIES
Water is an incolor, inodorous and insipid liquid (at normal temperature).
CHEMICAL PROPERTIES
At normal temperature water (gas) reacts with metals and the reaction forms the metal oxide and hydrogen gas.
“Vasile Alecsandri” High School, Galati, Romania
INTRODUCTION
Water is one of the predominant component of Earth, with a major role in the survival of organisms.
The seas and oceans ocuppy 71% of the globe’s surface and in most cells water is approximately 60% of their weight. She is the principal solvent and the dispersion environment of different substances. Water helps at the substances transport and numerous chemical reactions. In the same time, she is present in the human body in 60%, and man’s daily consumption is 2,5 l in food and liquids.
GENERAL CHARACTERISATION
Melting point: 0 ºC.
Boiling point: 100 ºC.
Maxim density: 1g / cm3.
Density at 25 ºC: 0,99701g / cm3.
NATURAL STATE
WATER STRUCTURE
In liquid state each and every water molecule is asociated with two others water molecules through hydrogen links. These explains why water’s boiling temperature is so high (100 degreeds C at a pressure of 1 atm), comparative with the boiling points of oxygen's neighboured combinations with hydrogen elements in the periodic system.
In liquid state each and every water molecule is asociated with two others water molecules through hydrogen links. These explains why water’s boiling temperature is so high (100 degreeds C at a pressure of 1 atm), comparative with the boiling points of oxygen's neighboured combinations with hydrogen elements in the periodic system.
In solid state (ice) she has almost a double number of hydrogen links than in the liquid state. Here are two hypothetical networks of water molecules. Dark blue represents oxygen and red hydrogen. Magenta bonds are bonds within each water molecule, light blue bonds are hydrogen bonds between molecules. Some bonds extend up or down out of the plane of the diagram. Hydrogen-Oxygen bonds extending up are shown by a hydrogen atom superimposed on the oxygen. If a water molecule is show with only one bond, the other extends down. Hydrogen bonds in and out of the plane of the diagram are not shown.
In all ice structures known, hydrogen is in two-fold coordination with oxygen, and oxygen in fourfold (tetrahedral) coordination with hydrogen. This geometry is dictated by the bond structure of oxygen, not by considerations of ionic radius. In size terms the hydrogen is a mere bump on the oxygen atom. In all known forms of ice, the water molecules retain their identities as distinct molecules and bond to other molecules by hydrogen bonding
Ice is used as a refrigerating agent because it takes more energy to melt it than most other substances, due to strong hydrogen bonds. Melting ice remains at a constant 0°C (32F).
Because ice is less dense than water at 0°C (32F) a mass of ice occupies 9% more volume than an equal mass of water. This is why when water in pipes freezes it can cause the pipes to burst. Another important point about ice being less dense than water is that it floats.
In the following figures there are represented microscopic images of some snow crystals:
PHYSICAL PROPERTIES
Water is an incolor, inodorous and insipid liquid (at normal temperature).
CHEMICAL PROPERTIES
At normal temperature water (gas) reacts with metals and the reaction forms the metal oxide and hydrogen gas.
Chemical properties of water
by Andreea Verdes, XI B class
“Vasile Alecsandri” High School, Galati, Romania
“Vasile Alecsandri” High School, Galati, Romania
Experimentally it has been proved that water is a chemical combination very stable. She can be discomposed at over 1000C or with the help of the electrical current.
2H2O 
2H2+ O2
2H2+ O2Water is very reactive from the chemical way of thinking. She reacts in some conditions with metals, nonmetals, basic oxides, acid oxides.
a) The action of the water with the metals
Metals: potassium, calcium, sodium react violently with water at cold, with forming of hydroxide and degage of hydrogen:
Na + H2O NaOH + 1/2H2
NaOH + 1/2H2
Magnesium reacts with water at hot temperatures or in vapor state:
Mg + 2H2O Mg(OH)2 + H2
Mg(OH)2 + H2Aluminum is attacked by water only if it’s clean by the protective layer of oxide:
2Al + 6H2O 2Al(OH)3 + 3H2
2Al(OH)3 + 3H2Hot steel reacts with water in vapor state and it forms the ferro-ferric oxide
3Fe + 4H2O Fe3O4 + 4H2
Fe3O4 + 4H2Plumb, cupper, mercury, gold, silver aren’t attacked by water or the vapors of water.
Some metals corrode at the presence of water. The attack is more powerful in the presence of the oxygen and the dioxide of carbon.
b) The action of the water with the nonmetals
Chlorine in reaction with water forms the chlorine water:
Cl2 + H2O HCl + HClO
HCl + HClOHClO HCl + [O]
HCl + [O]Passing a current of vapours of water over the coke at the temperature of almost 1000C it forms a mixture of monoxide of carbon and hydrogen, named water gaze. The reaction has an industrial importance:
C + H2O CO + H2
CO + H2c) The action of water with oxides
Water reacts with metallic soluble oxides with formation of hydroxides.
One of the reactions of practical importance is constituted of the extinguishing of the chalk, reaction powerfully exothermal.
CaO + H2O Ca(OH)2 + Q
Ca(OH)2 + QThe hydroxide of calcium obtained is relatively little soluble in water and this is why at the extinguishing of the chalk it is obtained the so named milk of chalk, which represents a fine suspension of Ca(OH)2 in a saturated solution of hydroxide of calcium.
At the dissolving of hydroxide of sulphur in water it takes place a chemical reaction from which it results an acid solution, sulphurous acid.
SO2 + H2O H2SO3
H2SO3The reaction with carbide or carbora of calcium at CaC2 goes to the reaction of the forming of acetylene, organic substance utilized at the welding and the cut of metals in the oxyacetylene machine:
CaC2 + 2H2O 
HCCH + Ca(OH)2 + Q
HCCH + Ca(OH)2 + QA School Experiment
By Lidia Minza
"Vasile Alecsandri" High School, Galacti, Romania
Sodium will react with water to make sodium hydroxide base and hydrogen gas:
The reaction is exothermic enough to cause the flammable hydrogen gas to ignite explosively with oxygen in the atmosphere to make new water molecules:
For these reasons, sodium is usually kept under mineral oil to keep it from reacting with these common substances.
The indicator (phenolphthalein) shows that sodium hydroxide is produced: the solution changes to deep red.
All the alkali metals react with water to produce elementary hydrogen and the corresponding alkali hydroxides. The reactivity increases with increasing periodic number. The metals rubidium and cesium explode when brought into contact with oxygen.
This experiment was performed with XI B class from “Vasile Alecsandri” High School, Galati, Romania.
"Vasile Alecsandri" High School, Galacti, Romania
Sodium will react with water to make sodium hydroxide base and hydrogen gas:
The indicator (phenolphthalein) shows that sodium hydroxide is produced: the solution changes to deep red.
All the alkali metals react with water to produce elementary hydrogen and the corresponding alkali hydroxides. The reactivity increases with increasing periodic number. The metals rubidium and cesium explode when brought into contact with oxygen.
This experiment was performed with XI B class from “Vasile Alecsandri” High School, Galati, Romania.
Physical properties of water
by George Braileanu, XI B class
“Vasile Alecsandri” High School, Galati, Romania
The two extreme temperatures of water, of solidification and boiling at natural pressure are 0 ºC and 100 ºC in the Celsius scale.
Water is liquid a large interval of temperature (0 ºC and 100 ºC). This anomaly is attributed to the molecular association of water trough bonds of hydrogen.
The bonds of hydrogen are realized with the molecules which contain covalent hydrogen to a powerful electro-negative element which has small volume and electrons which do not participate.
The hydrogen bond is electrostatic, weaker than the covalent bond and it doesn’t imply in common posing of electrons.
The water density varies with temperature:
At freezing it forms a second bond of the hydrogen at the oxygen atom, reason why ice has an aerie structure which determines the growth of the volume and decrease of the density.
Through freezing waters increases its volume by 9 per cent. This explains why the buckets and glass break. The majority of liquids increase their volume of solidification. It is known that +4 ºC water has ρmax=1 g/cm3 which is because of the fact that the water is formed of (H2O)2; this means the existence of two bonds of hydrogen.
The water in vapor state is formed from free molecules (n=1)
“Vasile Alecsandri” High School, Galati, Romania
Water is liquid a large interval of temperature (0 ºC and 100 ºC). This anomaly is attributed to the molecular association of water trough bonds of hydrogen.
The bonds of hydrogen are realized with the molecules which contain covalent hydrogen to a powerful electro-negative element which has small volume and electrons which do not participate.
The hydrogen bond is electrostatic, weaker than the covalent bond and it doesn’t imply in common posing of electrons.
The water density varies with temperature:
Through freezing waters increases its volume by 9 per cent. This explains why the buckets and glass break. The majority of liquids increase their volume of solidification. It is known that +4 ºC water has ρmax=1 g/cm3 which is because of the fact that the water is formed of (H2O)2; this means the existence of two bonds of hydrogen.
Water’s physical properties
By João Araújo and Ruben Silva, 11º Zi
Escola Secundária de Loulé
Escola Secundária de Loulé
Due to its molecular structure and its hydrogen bonds water presents some special properties. An unusual feature of water is its anomalous expansion. It contracts with the drop in temperature, but at 4°C begins to expand, returning to his contract after solidification.
Life under frozen water. Credit: Wikipedia(http://pt.wikipedia.org/wiki/Imagem:H2O.jpg)
That explains why the water first freezes on the surface because the water that reaches a temperature of 0ºC becomes less dense than water at 4°C, which mean it stays at the surface. This phenomenon is also important for the maintenance of life in cold water, because makes the water at 4°C is at the bottom and holds more heat for the creatures that live there. The lower density is due to the holes in the three-dimensional hexagonal structure due to hydrogen bonds typical of ice.
Ice three-dimensional structure. Credit:NYU (http://www.nyu.edu/pages/mathmol/textbook/hbond_ice.gif))
Water’s Physical Constants
by Luis Martins, 11º Zi
Escola Secundária de Loulé
Internet Links
Portuguese
Wikipedia (http://pt.wikipedia.org/wiki/%C3%81gua)
A água (http://www.bragancanet.pt/agua/)
English
Wikipedia (http://en.wikipedia.org/wiki/Water)
Water Science for Schools (USGS) (http://ga.water.usgs.gov/edu/)
Ice structure (UWGB) (http://www.uwgb.edu/dutchs/petrolgy/Ice%20Structure.HTM)
Escola Secundária de Loulé
Internet Links
Portuguese
Wikipedia (http://pt.wikipedia.org/wiki/%C3%81gua)
A água (http://www.bragancanet.pt/agua/)
English
Wikipedia (http://en.wikipedia.org/wiki/Water)
Water Science for Schools (USGS) (http://ga.water.usgs.gov/edu/)
Ice structure (UWGB) (http://www.uwgb.edu/dutchs/petrolgy/Ice%20Structure.HTM)
Water’s Physical States
by Miguel Romão, 11º Zi Escola Secundária de Loulé
Water is found in several physical states. In the atmosphere it is in a gaseous state, resulting from the evaporation of wet all surfaces - seas, rivers and lakes; liquid form is the most common form of water, found on large deposits on the planet’s surface, like the oceans and seas (salt water), in rivers and lakes (freshwater) and also underground, forming the so-called aquifers. Finally, we can also find the water in solid form in the coldest regions of the planet, the poles and at high altitudes (not to mention our home freezers). The gaseous state, in the atmosphere, water can rush in liquid form, such as rain, dew or fog, or in solid state, such as snow or hail.
The importance of water isn’t only because of its extension on Earth’s surface but also because of its primordial importance on several processes that are conditioning of life and human activity.
Nonetheless its abundance, only 2.5% of the water of the planet is drinkable fresh water, which is the only water that is of potential human use.
The main source of fresh water is the rain that falls over land. About 65% of this water goes back to the atmosphere through the water cycle. The rest will be part of superficial water and part as aquifers.
Water is found in several physical states. In the atmosphere it is in a gaseous state, resulting from the evaporation of wet all surfaces - seas, rivers and lakes; liquid form is the most common form of water, found on large deposits on the planet’s surface, like the oceans and seas (salt water), in rivers and lakes (freshwater) and also underground, forming the so-called aquifers. Finally, we can also find the water in solid form in the coldest regions of the planet, the poles and at high altitudes (not to mention our home freezers). The gaseous state, in the atmosphere, water can rush in liquid form, such as rain, dew or fog, or in solid state, such as snow or hail.
The importance of water isn’t only because of its extension on Earth’s surface but also because of its primordial importance on several processes that are conditioning of life and human activity.
Nonetheless its abundance, only 2.5% of the water of the planet is drinkable fresh water, which is the only water that is of potential human use.
The main source of fresh water is the rain that falls over land. About 65% of this water goes back to the atmosphere through the water cycle. The rest will be part of superficial water and part as aquifers.
Drinking Water
by Andreea Verdes, XI B class
“Vasile Alecsandri” High School, Galati, Romania
Drinking water mustn’t contain animal and vegetal organisms; it is necessary to gratify requirements with a superior quality related to physical, chemical, biological and bacteriological donatives.
The input with water to urban dealings represents a big importance, because water must be treating before appending it to people.
For the water cleaning are used:
- ozone(O3);
- chlorine(Cl2);
- baclor(Ca(ClO)2)
- aktivin(NH2OH);
In the case of chlorine is used approximately 0, 1 mg chlorine for one liter water. A bigger amount of chlorine gives water a disagreeable taste and a bad smell.
American services add to drinking water a little sodium fluoride (NaF) for combating dental caries.
“Vasile Alecsandri” High School, Galati, Romania
Drinking water mustn’t contain animal and vegetal organisms; it is necessary to gratify requirements with a superior quality related to physical, chemical, biological and bacteriological donatives.
The input with water to urban dealings represents a big importance, because water must be treating before appending it to people.
For the water cleaning are used:
- ozone(O3);
- chlorine(Cl2);
- baclor(Ca(ClO)2)
- aktivin(NH2OH);
In the case of chlorine is used approximately 0, 1 mg chlorine for one liter water. A bigger amount of chlorine gives water a disagreeable taste and a bad smell.
American services add to drinking water a little sodium fluoride (NaF) for combating dental caries.
Where does water exist?
by Ruben Veríssimo, 11º Zi
Escola Secundária de Loulé
Around two thirds of the Earth's surface is covered by water, 97.2% of which is contained in all five oceans. The agglomeration of ice in Antarctica contains about 90% of all the existing drinking water on the planet. The water in the form of steam can be seen in the clouds, contributing to the Earth's albedo.Figure 1 presents the water cycle on Earth.
Figure 1. Earth's water cycle
A satellite that seems to be made of water is Jupiter’s moon Europa. On the surface water is frozen but it is thought to have liquid water beneath it.
Comets also contain some water on their ice. It should be understood that when we talk about ice in the comets we are mostly talking about gases like carbon dioxide in a solid state.
Escola Secundária de Loulé
Around two thirds of the Earth's surface is covered by water, 97.2% of which is contained in all five oceans. The agglomeration of ice in Antarctica contains about 90% of all the existing drinking water on the planet. The water in the form of steam can be seen in the clouds, contributing to the Earth's albedo.Figure 1 presents the water cycle on Earth.
Figure 1. Earth's water cycle
A satellite that seems to be made of water is Jupiter’s moon Europa. On the surface water is frozen but it is thought to have liquid water beneath it.
Comets also contain some water on their ice. It should be understood that when we talk about ice in the comets we are mostly talking about gases like carbon dioxide in a solid state.
Water and its importance for human life
by Andreea Alexe, XI B class
“Vasile Alecsandri” High School, Galati, Romania
“Vasile Alecsandri” High School, Galati, Romania
Drinking water is as vital to man as air is. A human being drinks around 2 liters of water per day. Without water, man cannot survive more than a few days. A liter of water contains up to 0,5 grams of dissolved minerals and small amount of iron as well.
Mineral water contains minerals and carbon dioxide. It is recommended especially during the summer days when a human being loses a great amount of minerals through perspiration.
Water anomaly: All the substances may contract themselves when their temperature drops, thus shrinking the volume they occupy in space. If we introduce a solid substance in a bowl where there is the very same substance but in a liquid state, we shall notice that the solid substance sinks in the liquid. Water is the only known substance in nature that is an exception to this rule. If the temperature of the water drops up to 4 Celsius degrees, it will behave as the other substances: it increases its volume while its density decreases; however, at 0 centigrade it freeze but up to now its density is little enough and its volume large enough to make ice float on water and not sink into it.
Water as a solvent: many of the compound substances that are necessary for the existence of life may be dissolved into water. While the raindrops take shape and move around in the atmosphere, the hydrogen, oxygen and the carbon dioxide are some of the gases that dissolve themselves within these raindrops.
Depending directly on the weather conditions, the effective water volume, its space distribution and the Earth’s hydrological structure are also subject to the influences exercised by the geological structure, the great relief complexes, the degree and the type of vegetation layer.
As a primary environment for the emergence of the living matter, as an extremely important element for the natural complex that serves as a framework for the existence and activity of the human society, water has always had an outmost importance for that matter. Its importance is doubled by its role and use in the production of material goods and in their transportation, as well.
The economic importance of the planetary ocean
The planetary ocean occupies approx. 71% of the surface of the Earth and it represents an invaluable source of food, water, raw materials, energy and a priceless means of transport.
If we take into consideration all these related aspects of its meaning for the society, the role that it exercises over weather, waters and the hydro energetic potential of some continental regions, we should note that it represents an equally important category of indirect aspects of the relationship between man and the hydrosphere.
The planetary ocean as a source of food. Depending on its physical but mostly chemical characteristics, the oceanic waters fulfill, up to 200 meters from the surface level, all the conditions that favor the existence of an impressive amount of biomass that is commonly concentrated in the superficial layers that happen to be the most fertile. Although the thickness of the fertile water level is incomparably greater than that of the fertile soil (approx. 1 m) and although the productive potential of the marine waters is three times greater at a volume of 1m3 from the ground,, although these waters are richer is animal organisms that the dry land and are populated by quite a rich and diverse vegetal world and all the organisms reproduce instantly, this colossal supply has been turned into a good account only to an insignificant extend.
From the systematic fish categories we note those that have a significant economic value: Scombridae – the Atlantic mackerel, tone and the chub mackerel, Gadidae – cod and the haddock, salmodinae - especially in the northern part of the Pacific Ocean, and Clupeidaes -herring, sardines and shads.
Apart from fishing from the waters of the seas and oceans many aquatic as well as semi aquatic mammal are being hunted for fat, meat, leather and even furs , .i.e. seal, morsel, whale ( that today is in a number of approx. 1,000,000 only in the north of the Pacific and in the great circum Artic because excessive hunting overcame the rhythm of reproduction: for a few year the whale is being protected via international limitative conventions)
In the tropical seas around the Australia, in Polynesia, the Sea of Southern China people fish clams and shell fish that are extremely asked for: lobsters, crayfish, shrimps. Seaweeds represent only 45 of the organic mass that is annually obtained from the ocean and even though they may be used as food, fertilizers or raw material for the Chemical industry, they are not sufficiently exploited.
The sea as a source of fresh water. The real demographic explosion from the modern times associated with the demands of a more diversified and complex technological progress leads to a continuous increase of the necessary amount of both drinking and industrial water. This necessity is more acute when it comes to the development of an area that does not have enough continental waters of even continental waters that are sufficiently mineralized and in dry area that are situated within the tropical climate.
The planetary ocean as a source of raw material. Taking the shape of a solution with different concentrations or sediments, the marine waters contain an important supply of raw mineral matter. These supplies are estimated at extremely high values but the decreased profitability of the exploitation techniques does not allow but a small amount of their being turned into good account.
Out of the total quantity of salts that represent the medium salinity of marine and oceanic waters and that, if evaporated, would cover these basins with a layer of approx. 45 cm thick, the highest quantity is represented by the sodium chlorine. Out of the respective slats one may also extract magnesium ( that is needed for light alloys and in the industry of refractory materials: 75% of the total magnesium production of the USA comes from the sea) , potassium ( on the shore of the Red Sea, in Ethiopia, in the Mediterranean Basin – Naples area, the Far East – Japan, China, in western Australia), brome ( in USA, United Kingdom, India, Argentina, Canada, Japan)
The planetary ocean as a source of energy. The rhythmical or non-rhythmical dynamics of the oceanic waters, as well as the differences in vertical temperatures may be quite efficiently exploited as energy sources.
Known and used for a very long time, although to a small extend, the tides ( “the green coal”) that go over 8m in difference between the flood and the ebb, in bays, estuaries and straits may act as energy generators. Neglected fro a long time, the energy of the tides is being studied today and some of the most favourable regions in this matter are: Bretagne, Hudson Bay, the White Sea, the north-eats of the Arabic Sea, the sea of Eastern China, the Atlantic shore of the USA and Canada, the Pacific shore of Alaska.
In the warm regions of the ocean one may also obtain hydrothermal energy, in the Abidjan for example.
The oceanic water represents an impressive source of raw matter for the nuclear energy of the future (deuterium).
The sea as a means of transport. In spite of all difficulties that were due to the weather or the rudimentary technique that was used in the beginning of sailing, the sea has always represented the easiest means of transportation. The configuration of the oceanic and maritime basins, the presence of the peninsulas or of the islands as resting points when people did not use to sail at large explains why some areas knew an early development.
The dynamics of the maritime waters continues to exert a significant influence of transportation.
The potential of the sea for tourism and spas. Besides the many varied possibilities that it offer to society in point of the production of goods and transportation, the offers at the same time an essential potential for tourism and spas in many regions. Unlike many of the ways in which it has been exploited, this potential has only been used recently, from the second half of the 19th century and resulted from the development of the urban life and the consequent need to relax.
The spa value of the sea shore is due to the climatic particularities that favours helio marine treatment in which the total quantity of direct and diffuse radiation, the ultraviolet and aerosols quantity has an important role and which is indicated for the healing of many diseases, such as: bone tuberculosis, rickets, different ailments of the respiratory apparatus.
From a tourist point of view, the attraction of the sea shore resides in the many possibilities of toning the body and of relaxing by practicing water sports.
The economic importance of the continental waters
Although in less quantities than that of the planetary ocean, continental waters as more intensely used. This phenomenon is explained by the fact that water is primarily necessary for the human beings, for the vegetal as well as the anima worlds ( the internal circuits of the living beings, photosynthesis, perspiration, an so on). Of course that this intense use focuses of the sources of free, non-chemically, physically or biologically related (composition or crystallizing water) water sources that are more easily exploited.
The depth of the underground water is very important for the agricultural economy as it is a stated fact that the many type of cultures depend, among other things, on the depth of the water.
Many underground water layers that are captive in the dry area lack the possibility of being efficiently supplied, fact which leads to them having a fossil character and a flow that is continuously decreasing.
The underground cave waters are extremely whimsical in point of their spread, flow and volume. Although they represent an appreciable supply they are quite difficult to detect.
Besides underground waters, but more intensely used, are the ground waters that are necessary for the existence of the human society not only from a biological point of view but from that of the production of material goods as well. Out of the many branches of this production the most sensitive and dependent is by all means, agriculture.
Use of water in agriculture
As everyone knows, the plants do not need the same amount of water – the necessary amount varies from one systematic category to the other as some plants thrive in a wet environment while other thrive in a dry environment. Thus, prairie as well as Mediterranean plants need a relatively reduce amount of water. Tropical plants, on the other hand, need a greater amount of water (cane sugar, rice)
Use of water in industry
Modern industry tends to become a greater and more exigent water consumer. Depending on their specificity, different industry branches have their own different needs, a fact that is usually decisive for the placement of that respective industrial unit within a corresponding distance form the water source.
With regard to the necessary amount of water, the specific water consumption is greater in the paper and celluloses industry, the industries of fibers and synthetic fibers, synthetic rubber and wool. The specific water consumption is of a medium value in the case of cotton, flax and ammonia industry, the industries of the steelworks, nitric acid, sodium products, sugar and alumni. The specific water consumption is lower with the following industries: copper, zinc, tin, coal cleaning, coke, sulphuric acid, pharmaceutics, soap, dairy, meat, canned food, alcohol and tobacco.
The thermal electrical plants use a huge amount of water especially now when steam turbines are more used than internal combustion engines.
The nuclear plant use a lot of water and this is a fact that limits the possibility of placing them anywhere. In the case of atomic and electrical plants than have been built so far, the specific consumptions overcomes two time that of the classical thermal electrical plants that use steam turbines. This necessity has also asked for their being placed on rivers with increased and constant flow and combined with installations to desalt water so that own consumption may be supplied too. The more diverse and richer the industrial profile of an area is, the greater the water necessity – thus, the local supply can exhaust and this is a fact that would necessitate water to be brought from further distances.
Another aspect of water usage in industry is represented by the hydraulic energy and its being converted into other energy forms. With a view of producing the necessary amount of electrical energy, the hydro energetic potential of any river is nothing else but a direct consequence of its flow as well as of its fall. On the other hand, water cannot be accumulated but via damps. Thus, indirectly, the hydro energetic potential depends on the morphological as well as soil particularities of the valley which may or may not favour the building of a damp. The areas that best favors this type of constructions are the passes that were dug in hard rock as well as glacial steps.
Of secondary importance for industry, but not to be neglected, is the presence in some of the surface waters of some salt concentrations that may be exploited and that are used as raw material.
An extremely importance aspect of industry is constituted by water supply not only for the population but for the urban settlements as well and is related to the many facets of human activity. This issue is becoming more and more complicated because the necessary amount of water for the cities is increasing continuously.
The importance of continental waters for sailing. The hydrographical structure as well as the lakes are important means of transportation and their orientation is determined naturally, however sometimes they are not oriented to be most useful to people. This is why the interventions with a view to reorient or recreate some of these ways are quite frequent. Generally speaking, the capacity for transportation of the continental waters is less than that of the oceans as is only allows low weights. A series of hydrologic characteristics as well as some particularities of the morphology of the fluvial valleys are less favourable for sailing. The high amount of solid flows influence sailing in a negative way, especially on the inferior part of the rivers and mostly in deltas where – because of the continuous sedimentation of rich mud deposits – large floating island may be formed functioning, thus as genuine barriers, infringing sailing.
The hydrographical structures that are characterized by lower liquid flows are better use for floating, especially in the fir-trees wooden area, with less dense and easily floating wood.
The influence of man of hydrosphere
Human action upon the planetary ocean. The oldest and most spread way of transformation is the modification of the coastline, the position of the shore by gaining ground under the sea level. This activity is successful where it is combined with other natural processes that are spontaneously directed towards the same sense: along the accumulation shores, where the currents and the waves build sand belts, the winds – dunes and the rivers – deltas.
A human action developed not at surface but vertically, is that which is related to the depth of the bottom of the sea, near the shore with a view to anchor and dock the ships that carry huge amounts.
Towards these systematic actions the society has realized a series of important modifications of the sea bottom by way of artificial sedimentation.
With a view of moderating the weather of some regions, there have been implemented projects that aim at intervening on the volume of the sea waters.
The transformation of the continental waters by man.
Taking into account the fact that the decreased amount of the continental waters, as well as their contingency with the life and the activity of the human society, they bear a more advanced process of transformation. Within the process of transforming the hydrographical structure, one of the most common actions is that of changing the course of a river. This means a series of measures with a view to ensure navigability, to fight floods, to increase the possibilities of irrigation, water supply and to increase the surface of the agricultural fields.
The most important changes brought by man in the hydrological as well as morphological habitat of the hydrographical structure is due to the building of the damps. Another aspect is represented by the creation of new water courses.
The navigation channels also increase, although artificially the navigable hydrographic structure in the areas of less high relief and with a developed economy.
The action of the society upon the lakes has manifested quite early has has been oriented quite frequently towards the decrease of the natural surfaces in order to create agricultural fields.
The drainage of the lakes with the view to extract some mineral riches was also practiced. The action of the man upon the lakes was manifested with a view to increase their volume by way of damps and to create tanks used in hydro technical works. Man increased the network of lakes by creating artificial ones.
The action on man upon underground waters takes place as a consequence of different use of the land and of hydro alimentation works.
Thus, draining and drying a land determines the decrease of the underground waters as well as of the hydrostatic level under some of the cities due to the considerable diminishing of infiltrations.
Chemistry, due to the fact that is to be blamed, is preoccupied by pollution for two main reasons. On the one hand we may speak about the fact that during production, transportation and distribution of the chemical products there are many contaminations. And on the other hand, the pollution phenomena are analyzed and studied by chemists that propose solutions to control or to prevent them.
Water pollution
The waste waters that come from human dwellings, industry or agriculture end up in the waters of the rivers and lakes. These polluted waters contain substances that favour the development of bacteria. These bacteria need huge amount of the oxygen that is dissolved in water and thus endanger the life of plants and of animals as well. The waste waters also contain industrial and toxic products, such as lead and mercury.
The fertilizers that are so much in use in agriculture end up in the waters of the rivers and are carried away by the rain.
Mineral water contains minerals and carbon dioxide. It is recommended especially during the summer days when a human being loses a great amount of minerals through perspiration.
Water anomaly: All the substances may contract themselves when their temperature drops, thus shrinking the volume they occupy in space. If we introduce a solid substance in a bowl where there is the very same substance but in a liquid state, we shall notice that the solid substance sinks in the liquid. Water is the only known substance in nature that is an exception to this rule. If the temperature of the water drops up to 4 Celsius degrees, it will behave as the other substances: it increases its volume while its density decreases; however, at 0 centigrade it freeze but up to now its density is little enough and its volume large enough to make ice float on water and not sink into it.
Water as a solvent: many of the compound substances that are necessary for the existence of life may be dissolved into water. While the raindrops take shape and move around in the atmosphere, the hydrogen, oxygen and the carbon dioxide are some of the gases that dissolve themselves within these raindrops.
Depending directly on the weather conditions, the effective water volume, its space distribution and the Earth’s hydrological structure are also subject to the influences exercised by the geological structure, the great relief complexes, the degree and the type of vegetation layer.
As a primary environment for the emergence of the living matter, as an extremely important element for the natural complex that serves as a framework for the existence and activity of the human society, water has always had an outmost importance for that matter. Its importance is doubled by its role and use in the production of material goods and in their transportation, as well.
The economic importance of the planetary ocean
The planetary ocean occupies approx. 71% of the surface of the Earth and it represents an invaluable source of food, water, raw materials, energy and a priceless means of transport.
If we take into consideration all these related aspects of its meaning for the society, the role that it exercises over weather, waters and the hydro energetic potential of some continental regions, we should note that it represents an equally important category of indirect aspects of the relationship between man and the hydrosphere.
The planetary ocean as a source of food. Depending on its physical but mostly chemical characteristics, the oceanic waters fulfill, up to 200 meters from the surface level, all the conditions that favor the existence of an impressive amount of biomass that is commonly concentrated in the superficial layers that happen to be the most fertile. Although the thickness of the fertile water level is incomparably greater than that of the fertile soil (approx. 1 m) and although the productive potential of the marine waters is three times greater at a volume of 1m3 from the ground,, although these waters are richer is animal organisms that the dry land and are populated by quite a rich and diverse vegetal world and all the organisms reproduce instantly, this colossal supply has been turned into a good account only to an insignificant extend.
From the systematic fish categories we note those that have a significant economic value: Scombridae – the Atlantic mackerel, tone and the chub mackerel, Gadidae – cod and the haddock, salmodinae - especially in the northern part of the Pacific Ocean, and Clupeidaes -herring, sardines and shads.
Apart from fishing from the waters of the seas and oceans many aquatic as well as semi aquatic mammal are being hunted for fat, meat, leather and even furs , .i.e. seal, morsel, whale ( that today is in a number of approx. 1,000,000 only in the north of the Pacific and in the great circum Artic because excessive hunting overcame the rhythm of reproduction: for a few year the whale is being protected via international limitative conventions)
In the tropical seas around the Australia, in Polynesia, the Sea of Southern China people fish clams and shell fish that are extremely asked for: lobsters, crayfish, shrimps. Seaweeds represent only 45 of the organic mass that is annually obtained from the ocean and even though they may be used as food, fertilizers or raw material for the Chemical industry, they are not sufficiently exploited.
The sea as a source of fresh water. The real demographic explosion from the modern times associated with the demands of a more diversified and complex technological progress leads to a continuous increase of the necessary amount of both drinking and industrial water. This necessity is more acute when it comes to the development of an area that does not have enough continental waters of even continental waters that are sufficiently mineralized and in dry area that are situated within the tropical climate.
The planetary ocean as a source of raw material. Taking the shape of a solution with different concentrations or sediments, the marine waters contain an important supply of raw mineral matter. These supplies are estimated at extremely high values but the decreased profitability of the exploitation techniques does not allow but a small amount of their being turned into good account.
Out of the total quantity of salts that represent the medium salinity of marine and oceanic waters and that, if evaporated, would cover these basins with a layer of approx. 45 cm thick, the highest quantity is represented by the sodium chlorine. Out of the respective slats one may also extract magnesium ( that is needed for light alloys and in the industry of refractory materials: 75% of the total magnesium production of the USA comes from the sea) , potassium ( on the shore of the Red Sea, in Ethiopia, in the Mediterranean Basin – Naples area, the Far East – Japan, China, in western Australia), brome ( in USA, United Kingdom, India, Argentina, Canada, Japan)
The planetary ocean as a source of energy. The rhythmical or non-rhythmical dynamics of the oceanic waters, as well as the differences in vertical temperatures may be quite efficiently exploited as energy sources.
Known and used for a very long time, although to a small extend, the tides ( “the green coal”) that go over 8m in difference between the flood and the ebb, in bays, estuaries and straits may act as energy generators. Neglected fro a long time, the energy of the tides is being studied today and some of the most favourable regions in this matter are: Bretagne, Hudson Bay, the White Sea, the north-eats of the Arabic Sea, the sea of Eastern China, the Atlantic shore of the USA and Canada, the Pacific shore of Alaska.
In the warm regions of the ocean one may also obtain hydrothermal energy, in the Abidjan for example.
The oceanic water represents an impressive source of raw matter for the nuclear energy of the future (deuterium).
The sea as a means of transport. In spite of all difficulties that were due to the weather or the rudimentary technique that was used in the beginning of sailing, the sea has always represented the easiest means of transportation. The configuration of the oceanic and maritime basins, the presence of the peninsulas or of the islands as resting points when people did not use to sail at large explains why some areas knew an early development.
The dynamics of the maritime waters continues to exert a significant influence of transportation.
The potential of the sea for tourism and spas. Besides the many varied possibilities that it offer to society in point of the production of goods and transportation, the offers at the same time an essential potential for tourism and spas in many regions. Unlike many of the ways in which it has been exploited, this potential has only been used recently, from the second half of the 19th century and resulted from the development of the urban life and the consequent need to relax.
The spa value of the sea shore is due to the climatic particularities that favours helio marine treatment in which the total quantity of direct and diffuse radiation, the ultraviolet and aerosols quantity has an important role and which is indicated for the healing of many diseases, such as: bone tuberculosis, rickets, different ailments of the respiratory apparatus.
From a tourist point of view, the attraction of the sea shore resides in the many possibilities of toning the body and of relaxing by practicing water sports.
The economic importance of the continental waters
Although in less quantities than that of the planetary ocean, continental waters as more intensely used. This phenomenon is explained by the fact that water is primarily necessary for the human beings, for the vegetal as well as the anima worlds ( the internal circuits of the living beings, photosynthesis, perspiration, an so on). Of course that this intense use focuses of the sources of free, non-chemically, physically or biologically related (composition or crystallizing water) water sources that are more easily exploited.
The depth of the underground water is very important for the agricultural economy as it is a stated fact that the many type of cultures depend, among other things, on the depth of the water.
Many underground water layers that are captive in the dry area lack the possibility of being efficiently supplied, fact which leads to them having a fossil character and a flow that is continuously decreasing.
The underground cave waters are extremely whimsical in point of their spread, flow and volume. Although they represent an appreciable supply they are quite difficult to detect.
Besides underground waters, but more intensely used, are the ground waters that are necessary for the existence of the human society not only from a biological point of view but from that of the production of material goods as well. Out of the many branches of this production the most sensitive and dependent is by all means, agriculture.
Use of water in agriculture
As everyone knows, the plants do not need the same amount of water – the necessary amount varies from one systematic category to the other as some plants thrive in a wet environment while other thrive in a dry environment. Thus, prairie as well as Mediterranean plants need a relatively reduce amount of water. Tropical plants, on the other hand, need a greater amount of water (cane sugar, rice)
Use of water in industry
Modern industry tends to become a greater and more exigent water consumer. Depending on their specificity, different industry branches have their own different needs, a fact that is usually decisive for the placement of that respective industrial unit within a corresponding distance form the water source.
With regard to the necessary amount of water, the specific water consumption is greater in the paper and celluloses industry, the industries of fibers and synthetic fibers, synthetic rubber and wool. The specific water consumption is of a medium value in the case of cotton, flax and ammonia industry, the industries of the steelworks, nitric acid, sodium products, sugar and alumni. The specific water consumption is lower with the following industries: copper, zinc, tin, coal cleaning, coke, sulphuric acid, pharmaceutics, soap, dairy, meat, canned food, alcohol and tobacco.
The thermal electrical plants use a huge amount of water especially now when steam turbines are more used than internal combustion engines.
The nuclear plant use a lot of water and this is a fact that limits the possibility of placing them anywhere. In the case of atomic and electrical plants than have been built so far, the specific consumptions overcomes two time that of the classical thermal electrical plants that use steam turbines. This necessity has also asked for their being placed on rivers with increased and constant flow and combined with installations to desalt water so that own consumption may be supplied too. The more diverse and richer the industrial profile of an area is, the greater the water necessity – thus, the local supply can exhaust and this is a fact that would necessitate water to be brought from further distances.
Another aspect of water usage in industry is represented by the hydraulic energy and its being converted into other energy forms. With a view of producing the necessary amount of electrical energy, the hydro energetic potential of any river is nothing else but a direct consequence of its flow as well as of its fall. On the other hand, water cannot be accumulated but via damps. Thus, indirectly, the hydro energetic potential depends on the morphological as well as soil particularities of the valley which may or may not favour the building of a damp. The areas that best favors this type of constructions are the passes that were dug in hard rock as well as glacial steps.
Of secondary importance for industry, but not to be neglected, is the presence in some of the surface waters of some salt concentrations that may be exploited and that are used as raw material.
An extremely importance aspect of industry is constituted by water supply not only for the population but for the urban settlements as well and is related to the many facets of human activity. This issue is becoming more and more complicated because the necessary amount of water for the cities is increasing continuously.
The importance of continental waters for sailing. The hydrographical structure as well as the lakes are important means of transportation and their orientation is determined naturally, however sometimes they are not oriented to be most useful to people. This is why the interventions with a view to reorient or recreate some of these ways are quite frequent. Generally speaking, the capacity for transportation of the continental waters is less than that of the oceans as is only allows low weights. A series of hydrologic characteristics as well as some particularities of the morphology of the fluvial valleys are less favourable for sailing. The high amount of solid flows influence sailing in a negative way, especially on the inferior part of the rivers and mostly in deltas where – because of the continuous sedimentation of rich mud deposits – large floating island may be formed functioning, thus as genuine barriers, infringing sailing.
The hydrographical structures that are characterized by lower liquid flows are better use for floating, especially in the fir-trees wooden area, with less dense and easily floating wood.
The influence of man of hydrosphere
Human action upon the planetary ocean. The oldest and most spread way of transformation is the modification of the coastline, the position of the shore by gaining ground under the sea level. This activity is successful where it is combined with other natural processes that are spontaneously directed towards the same sense: along the accumulation shores, where the currents and the waves build sand belts, the winds – dunes and the rivers – deltas.
A human action developed not at surface but vertically, is that which is related to the depth of the bottom of the sea, near the shore with a view to anchor and dock the ships that carry huge amounts.
Towards these systematic actions the society has realized a series of important modifications of the sea bottom by way of artificial sedimentation.
With a view of moderating the weather of some regions, there have been implemented projects that aim at intervening on the volume of the sea waters.
The transformation of the continental waters by man.
Taking into account the fact that the decreased amount of the continental waters, as well as their contingency with the life and the activity of the human society, they bear a more advanced process of transformation. Within the process of transforming the hydrographical structure, one of the most common actions is that of changing the course of a river. This means a series of measures with a view to ensure navigability, to fight floods, to increase the possibilities of irrigation, water supply and to increase the surface of the agricultural fields.
The most important changes brought by man in the hydrological as well as morphological habitat of the hydrographical structure is due to the building of the damps. Another aspect is represented by the creation of new water courses.
The navigation channels also increase, although artificially the navigable hydrographic structure in the areas of less high relief and with a developed economy.
The action of the society upon the lakes has manifested quite early has has been oriented quite frequently towards the decrease of the natural surfaces in order to create agricultural fields.
The drainage of the lakes with the view to extract some mineral riches was also practiced. The action of the man upon the lakes was manifested with a view to increase their volume by way of damps and to create tanks used in hydro technical works. Man increased the network of lakes by creating artificial ones.
The action on man upon underground waters takes place as a consequence of different use of the land and of hydro alimentation works.
Thus, draining and drying a land determines the decrease of the underground waters as well as of the hydrostatic level under some of the cities due to the considerable diminishing of infiltrations.
Chemistry, due to the fact that is to be blamed, is preoccupied by pollution for two main reasons. On the one hand we may speak about the fact that during production, transportation and distribution of the chemical products there are many contaminations. And on the other hand, the pollution phenomena are analyzed and studied by chemists that propose solutions to control or to prevent them.
Water pollution
The waste waters that come from human dwellings, industry or agriculture end up in the waters of the rivers and lakes. These polluted waters contain substances that favour the development of bacteria. These bacteria need huge amount of the oxygen that is dissolved in water and thus endanger the life of plants and of animals as well. The waste waters also contain industrial and toxic products, such as lead and mercury.
The fertilizers that are so much in use in agriculture end up in the waters of the rivers and are carried away by the rain.
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