11

SAVE WATER!SAVE WATER!SAVE LIFE!SAVE LIFE!

22

PlanPlan– In our presentation, we will follow the following plan:In our presentation, we will follow the following plan:

• 1) Water as the cradle of life1) Water as the cradle of life• 2) Physical and chemical properties of water2) Physical and chemical properties of water• 3) Pollution of water3) Pollution of water

33

Water – the cradle of lifeWater – the cradle of life

Part 1Part 1

44

Water – the cradle of lifeWater – the cradle of life• For proving the importance of water for the birth of life, we For proving the importance of water for the birth of life, we

will take a look at the as known chemical evolution – the will take a look at the as known chemical evolution – the transition from inorganic materials to the simplest and transition from inorganic materials to the simplest and fundamental form of life as we know it – the first cells. fundamental form of life as we know it – the first cells.

• The cells are the basic structure, metabolic and functional The cells are the basic structure, metabolic and functional unit of organisms. unit of organisms.

• The evolution of life after the creation of cells is known as The evolution of life after the creation of cells is known as biological evolution, and we are not going into it in this biological evolution, and we are not going into it in this presentation. presentation.

55

This tree shows the evolution of primary chemical elements until the forming of life as we know it. Notice that the greater part of evolution is before the formation of the first cells.

66

First cells

Primary Earth

Chemical

evolution

Biological

evolution

Conventional borderProtobionts

Low mass organicInitial gases

Biopolymers

CO

H2OCO2

NH3H2

CH4

NO2

aggregates

Biopolymers

Protobionts

1

2

3

4

5

Life as we know it

N2

77

Initial gasesInitial gases 1 stage1 stage

• 1.1. Probably during the early stages of Probably during the early stages of the Earth’s existence the Earth’s existence there were violent volcanic eruptions on the whole surface, there were violent volcanic eruptions on the whole surface, congestion of the Earth’s crust and separation of a high congestion of the Earth’s crust and separation of a high amount of heat. The gases (water vapours, hydrogen, amount of heat. The gases (water vapours, hydrogen, methane, ammonia), coming from the hot semi-fluid interior methane, ammonia), coming from the hot semi-fluid interior of the Earth, formed the atmosphere. It contained the basic of the Earth, formed the atmosphere. It contained the basic materials for the formation of organic combinations.materials for the formation of organic combinations.

Active volcanoesCO

H2OCO2NH3

H2CH

4

NO2

N2

88

2 stage2 stage

• The gThe gases, contained in the atmosphere, ases, contained in the atmosphere, reacted with each other reacted with each other and formed organic molecules. The energy for this synthesis and formed organic molecules. The energy for this synthesis came from the lightning and the ultra-violet radiation. came from the lightning and the ultra-violet radiation. Gradually Gradually the Earth became cold and when the temperature fell the Earth became cold and when the temperature fell below below 100˚С100˚С, the water vapours began to condense, the rain , the water vapours began to condense, the rain evaporated from the hot surface and this initiated the circle of evaporated from the hot surface and this initiated the circle of water. water. The folding proccesses The folding proccesses led to the forming of giant hollows. led to the forming of giant hollows. They filled with water and formed the oceans and the seas.They filled with water and formed the oceans and the seas.

MethaneBenzeneSoap

99

Miller’s experimentMiller’s experiment• An evidence for this is the An evidence for this is the

experiment of Stanley Miller. experiment of Stanley Miller. He invented a device in which He invented a device in which ammonia, methane, hydrogen ammonia, methane, hydrogen and water vapours circulated and water vapours circulated and through the mixture and through the mixture passed an electric spark. passed an electric spark. During the circulation the During the circulation the water cooled and fell like a water cooled and fell like a “rain”. After a week in the “rain”. After a week in the liquid were found amino acids. liquid were found amino acids. It is perfectly possible that the It is perfectly possible that the same processes happened in same processes happened in the atmosphere.the atmosphere.

1010

3 stage3 stage

• Some primitive nucleic acidsSome primitive nucleic acids acquired matrix ability and were able to acquired matrix ability and were able to form a copy of themselves. The macromolecules with opposite form a copy of themselves. The macromolecules with opposite charges stuck together and formed aggregates - complexes of over-charges stuck together and formed aggregates - complexes of over-molecule level. The rain carried away the organic combinations in molecule level. The rain carried away the organic combinations in the oceans and the seas, where the so-called “organic soup” formed.the oceans and the seas, where the so-called “organic soup” formed.

• The simple organic combinations reacted with each other and The simple organic combinations reacted with each other and formed simple formed simple albumenalbumenss, nucleic acid, nucleic acids, carbohydrates and lipids, s, carbohydrates and lipids, which constantly evolved. The albumens formed which constantly evolved. The albumens formed hydrophilichydrophilic colloidal complexes, whichcolloidal complexes, which attracted the water molecules. attracted the water molecules.

1111

• On the surface of some coacervates more lipids and albumens gathered On the surface of some coacervates more lipids and albumens gathered and formed a double molecule layer. With time the cover of some and formed a double molecule layer. With time the cover of some coacervates became permeable and some reactions which released coacervates became permeable and some reactions which released energy began. The membrane gave stability to the coacervates. This is energy began. The membrane gave stability to the coacervates. This is the precellular period in the evolution of organic matter.the precellular period in the evolution of organic matter.

4 stage4 stage

• Enzymes were formed in the coacervates through absorbing metal Enzymes were formed in the coacervates through absorbing metal ions. Some combinations of the organic molecules in the coacervates ions. Some combinations of the organic molecules in the coacervates became became stable and stable and added to their added to their organization, while others were organization, while others were destroyed. The complexes of over-molecule level in them were much destroyed. The complexes of over-molecule level in them were much more complicated than these in the environment.more complicated than these in the environment.

• The coacervates are very small drops, which have osmotic characteristics. The coacervates are very small drops, which have osmotic characteristics. Around the complexes of over-molecule level a water cover differentiated. Around the complexes of over-molecule level a water cover differentiated. In this system the molecules interacted with each other and new molecules In this system the molecules interacted with each other and new molecules entered through the cover, thus enlarging the drop. entered through the cover, thus enlarging the drop.

Coacervate

1212

5 stage5 stage

• Molecules which already existed in the organic soup and could Molecules which already existed in the organic soup and could replicate were included in the coacervates. As a result of this a replicate were included in the coacervates. As a result of this a rearrangement of the interior contents began. The transport of rearrangement of the interior contents began. The transport of materials through the cellular membrane perfected. The nucleic materials through the cellular membrane perfected. The nucleic acids established control over the basic life processes. The protocells acids established control over the basic life processes. The protocells could split and share their genetic program with their filial cells. The could split and share their genetic program with their filial cells. The cellular period of the evolution of the animate nature began.cellular period of the evolution of the animate nature began.

1313

• … … and life began …and life began …

1414

Properties of waterProperties of water

Part 2Part 2

1515

Water has no taste, no coloWater has no taste, no colouur, no odor, no odouur; it cannot be defined, r; it cannot be defined, art relished while ever mysterious. art relished while ever mysterious.

NNot necessary to life, but rather life itself. It fills us with a ot necessary to life, but rather life itself. It fills us with a gratificationgratification

that exceeds the delight of the senses.that exceeds the delight of the senses.

ANTOINE DE SAINT-EXUPERY (1900-1944), Wind, Sand, and Stars, 1939ANTOINE DE SAINT-EXUPERY (1900-1944), Wind, Sand, and Stars, 1939

1616

Planet, dominated by waterPlanet, dominated by water• We live on a planet that is We live on a planet that is

dominated by waterdominated by water..

• More than 70% of the Earth's surface More than 70% of the Earth's surface is covered with this simple molecule. is covered with this simple molecule. Scientists estimate that the Scientists estimate that the hydrospherehydrosphere contains about 1.36 contains about 1.36 billion cubic kilometers of this billion cubic kilometers of this substance mostly in the form of a substance mostly in the form of a liquid (water) that occupies liquid (water) that occupies topographic depressions on the topographic depressions on the Earth. The second most common Earth. The second most common form of the water molecule on our form of the water molecule on our planet is planet is iceice. If all our planet's ice . If all our planet's ice meltedmelted, sea-level , sea-level would rise by about would rise by about 70 meters.70 meters.

1717

• Water is also essential for life. Water is also essential for life. Water is the major constituent Water is the major constituent of almost all life forms. Most of almost all life forms. Most animals and plants contain animals and plants contain more than 60% water by more than 60% water by volume. Without water life volume. Without water life would probably never have would probably never have developed on our planet.developed on our planet.

1818

Structure of water molecule Structure of water molecule

• The two hydrogen atoms bound to one The two hydrogen atoms bound to one oxygen atom to form a 'V' shape with oxygen atom to form a 'V' shape with the hydrogen atomsthe hydrogen atoms at an angle of 105°.at an angle of 105°.

• When the hydrogen atoms combine with When the hydrogen atoms combine with oxygen, they each give away their single oxygen, they each give away their single electron andelectron and form a covalent bond.form a covalent bond. Because electrons are more attracted to Because electrons are more attracted to the positively charged oxygen atom, the the positively charged oxygen atom, the two hydrogenstwo hydrogens become slightly positively become slightly positively charged (they give away their negative charged (they give away their negative charge) and the oxygen atom becomes charge) and the oxygen atom becomes negatively charged.negatively charged.

Oxygen atomHydrogen atomCovalent bond

1919

+

--

Polar moleculePolar molecule

• This separation between negative and positive charges This separation between negative and positive charges produces a polar molecule, that is aproduces a polar molecule, that is a molecule that has an molecule that has an electrical charge on its surface.electrical charge on its surface. The hydrogen lobes have The hydrogen lobes have positive charges, and the oxygen atom on the opposite positive charges, and the oxygen atom on the opposite side has twoside has two negative charges (associated with two lobes.negative charges (associated with two lobes.))

2020

Hydrogen bondHydrogen bond• Because they are polarized, two Because they are polarized, two

adjacent H2O molecules can form a adjacent H2O molecules can form a linkage known as a hydrogenlinkage known as a hydrogen bond. bond.

• Hydrogen bonds have only Hydrogen bonds have only about 1/20 the strength of a about 1/20 the strength of a covalent bond. A hydrogen bond covalent bond. A hydrogen bond is therefore a weak chemical is therefore a weak chemical bond between a hydrogen atom bond between a hydrogen atom in one polarin one polar m molecule and a very olecule and a very electronegative atom of a electronegative atom of a second polar molecule.second polar molecule. The The hydrogen of one water molecule hydrogen of one water molecule will be attracted to the oxygen will be attracted to the oxygen of another water molecule.of another water molecule. TheTherere are usually 4-8 molecules are usually 4-8 molecules per group in liquid water. per group in liquid water.

+

-

2121

• The water molecules form hydrogen bonds, giving The water molecules form hydrogen bonds, giving shape to water as a liquid.shape to water as a liquid. Each single water Each single water molecule can form bonds with four other water molecule can form bonds with four other water molecules in a tetrahedralmolecules in a tetrahedral arrangement. Although arrangement. Although these bonds are weak they lead to many other these bonds are weak they lead to many other unique properties. unique properties.

2222

3 aggregate conditions3 aggregate conditions• Water is unique in that it is the Water is unique in that it is the

only natural substance that is only natural substance that is found in all three states -- found in all three states -- liquid, solid (ice), and gas liquid, solid (ice), and gas (steam) -- at the temperatures (steam) -- at the temperatures normally found on Earth. This normally found on Earth. This is becauseis because the the Earth is a very Earth is a very special planet with just the special planet with just the right range of temperatures right range of temperatures and air pressures.and air pressures. Earth's Earth's water is constantly interacting, water is constantly interacting, changing, and changing, and in movement.in movement. Water cycle.

• Water is found on Earth in all three Water is found on Earth in all three forms: liquid, solid, gas, and is forms: liquid, solid, gas, and is cycled though the water cyclcycled though the water cycle. e.

2323

Water propertiesWater properties

• Water is a tasteless, odourless Water is a tasteless, odourless liquid at ambient temperature and liquid at ambient temperature and pressure, and appears colourless, pressure, and appears colourless, although it has its own intrinsic although it has its own intrinsic very light blue hue. Ice also very light blue hue. Ice also appears coloappears colouurless, and water rless, and water vapor is essentially invisible as a vapor is essentially invisible as a gas. gas.

• TastelessTasteless• OdourlessOdourless• ColourlessColourless

• Water as a liquid has the following properties:Water as a liquid has the following properties:

2424

Transparency Transparency • Water is transparent, and thus aquatic Water is transparent, and thus aquatic

plants can live within the water plants can live within the water because sunlight can reach them. Only because sunlight can reach them. Only strong UV light is slightly absorbed.strong UV light is slightly absorbed.

2525

ConductivityConductivity• Conductivity is the Conductivity is the

ability of a substance ability of a substance to carry an electric to carry an electric current. current. • Water will conduct an Water will conduct an electric current only if electric current only if dissolved ions are dissolved ions are present because present because water molecules do water molecules do not act as a not act as a conductorconductor. Measuring . Measuring conductivity is a good conductivity is a good way to determine the way to determine the amount of dissolved amount of dissolved solids in a sample of solids in a sample of water and, thus, to water and, thus, to determine its puritydetermine its purity. .

2626

• If water worked like other liquids, If water worked like other liquids, then there would be no such then there would be no such thing as an ice berg, the ice in thing as an ice berg, the ice in your soft drink would sink to the your soft drink would sink to the bottom of the glass, and ponds bottom of the glass, and ponds would freeze from the bottom would freeze from the bottom up!up! The maximum density of The maximum density of water is at 3.98 °C (39.16 °F).water is at 3.98 °C (39.16 °F).

Water’s extensionWater’s extension

• Water becomes even less dense Water becomes even less dense upon freezing, expanding 9%. This upon freezing, expanding 9%. This causes an unusual phenomenon: causes an unusual phenomenon: ice floats upon water, and so ice floats upon water, and so water organisms can live inside a water organisms can live inside a partly frozen pond because the partly frozen pond because the water on the bottom has a water on the bottom has a temperature of around 4 °C temperature of around 4 °C (39 °F).(39 °F).

• Most liquids contract (get smaller) when they get colder. Water is Most liquids contract (get smaller) when they get colder. Water is differentdifferent - it - it contracts until it reaches 4 C then it expands until it is contracts until it reaches 4 C then it expands until it is solid. Solid water is less dense thasolid. Solid water is less dense thann liquid water because of this. liquid water because of this.

• The higher boiling point and melting The higher boiling point and melting point of water can be explained by the point of water can be explained by the hydrogen bonds that help hold groups hydrogen bonds that help hold groups of water molecules together. These of water molecules together. These hydrogen bonds must be broken hydrogen bonds must be broken before water molecules can escape before water molecules can escape into the air. This requires energy in the into the air. This requires energy in the form of heat. Molecules such as sulfur form of heat. Molecules such as sulfur dioxide and carbon dioxide do not have dioxide and carbon dioxide do not have hydrogen bonds and, consequently, hydrogen bonds and, consequently, require less energy to boil.require less energy to boil.

• Hydrogen bonding accounts for the Hydrogen bonding accounts for the strength of fibres in wood. It also helps strength of fibres in wood. It also helps explain some of the physical explain some of the physical characteristics of water. Water boils at characteristics of water. Water boils at 100°C and freezes at 0°C. By 100°C and freezes at 0°C. By comparison, sulfur dioxide, a molecule of comparison, sulfur dioxide, a molecule of similar size, boils at 62°C and freezes at similar size, boils at 62°C and freezes at -83°C. -83°C.

2727

Thermal capacityThermal capacity

• Water has one of the highest Water has one of the highest heat capacities of all substances. heat capacities of all substances.

• The large amount of water on The large amount of water on Earth means that extreme Earth means that extreme temperature changes are rare on temperature changes are rare on Earth compared to other planets.Earth compared to other planets.

• This means that it takes a This means that it takes a great deal of heat energy to great deal of heat energy to change the temperature of change the temperature of water compared to metals. water compared to metals.

2828

Thermal bufferThermal buffer• Were it not for the high heat capacity of water, our bodies Were it not for the high heat capacity of water, our bodies

(which also contain a large amount of water) would be subject (which also contain a large amount of water) would be subject to a great deal of temperature variation.to a great deal of temperature variation.

• By the two ways of defending against overheating (high heat By the two ways of defending against overheating (high heat capacity and high warmth of evaporation) water actually is an capacity and high warmth of evaporation) water actually is an ideal medium for life and ensures safe temperature conditions ideal medium for life and ensures safe temperature conditions in the organic systems. Thein the organic systems. They alsoy also allow water to moderate allow water to moderate Earth's climate by buffering large fluctuations in temperature.Earth's climate by buffering large fluctuations in temperature.

2929

AdhesionAdhesion

• Water has a partial negative charge (σ-) near the oxygen atom Water has a partial negative charge (σ-) near the oxygen atom duedue to to the unshared pairs of electrons, and partial positive the unshared pairs of electrons, and partial positive charges (σ+) near the hydrogen atoms. In water, this happens charges (σ+) near the hydrogen atoms. In water, this happens because the oxygen atom is more electronegative than the because the oxygen atom is more electronegative than the hydrogen atoms — that is, it has a stronger "pulling power" on hydrogen atoms — that is, it has a stronger "pulling power" on the molecule's electrons, drawing them closer (along with their the molecule's electrons, drawing them closer (along with their negative charge) and making the area around the oxygen atom negative charge) and making the area around the oxygen atom more negative than the area around both of the hydrogen atoms.more negative than the area around both of the hydrogen atoms.

• Water molecules stick to each other. This is Water molecules stick to each other. This is called cohesion. Water can also be attracted called cohesion. Water can also be attracted to other materials. This is called adhesion. to other materials. This is called adhesion.

3030

Capillary actionCapillary action• Capillary action is Capillary action is

related to the adhesive related to the adhesive properties properties of water. of water.

• Plants take advantage Plants take advantage ofof c capillary action to apillary action to pull water from thepull water from the earthearth into themselves. into themselves.

• You can see You can see ccapillary apillary action 'in action' by action 'in action' by placing a straw into a placing a straw into a glass of water. glass of water.

3131

gravity and the size of the gravity and the size of the straw. The thinner the straw or straw. The thinner the straw or tube the higher up tube the higher up ccapillary apillary action will pull the wateraction will pull the water..

The water 'climbs' up the straw.

• Capillary action is limited by ... Capillary action is limited by ...

• What is happening is that the What is happening is that the water molecules are attracted to water molecules are attracted to the straw molecules. When one the straw molecules. When one water molecule moves closer to water molecule moves closer to the straw molecules the other the straw molecules the other water molecules (which are water molecules (which are cohesively attracted to that water cohesively attracted to that water molecule) also move up into the molecule) also move up into the straw. straw.

3232

High surface tensionHigh surface tension

Surface tension is related to the Surface tension is related to the cohesivcohesivee properties properties of water of water

Water has a very high surface Water has a very high surface tension. In other words, water tension. In other words, water is sticky and elastic, and tends is sticky and elastic, and tends to clump together in drops to clump together in drops rather than spread out in a rather than spread out in a thin film. Surface tension is thin film. Surface tension is responsible for responsible for capillary capillary actionaction, which allows water , which allows water (and its dissolved substances) (and its dissolved substances) to move through the roots of to move through the roots of plants and through the tiny plants and through the tiny blood vessels in our bodiesblood vessels in our bodies

3333

• This phenomenon also causes This phenomenon also causes water to stick to the sides of water to stick to the sides of vertical structures despite vertical structures despite gravity's downward pull. Water's gravity's downward pull. Water's high surface tension allows for high surface tension allows for the formation of water droplets the formation of water droplets and waves, allows plants to and waves, allows plants to move water (and dissolved move water (and dissolved nutrients) from their roots to nutrients) from their roots to their leaves, and the movement their leaves, and the movement of blood through tiny vessels in of blood through tiny vessels in the bodies of some animals. the bodies of some animals.

This insect walks on the water’s surface

3434

Universal solventUniversal solvent

• Substances that will mix well and dissolve in Substances that will mix well and dissolve in water, e.g. salts, sugars, acids, alkalis, and water, e.g. salts, sugars, acids, alkalis, and some gases: especially oxygen, carbon some gases: especially oxygen, carbon dioxide (carbonation), are known as dioxide (carbonation), are known as “hydrophilic" (water-loving) substances, “hydrophilic" (water-loving) substances, while those that do not mix well with water while those that do not mix well with water (e.g. fats and oils), are known as (e.g. fats and oils), are known as “hydrophobic" (water-fearing) substances.“hydrophobic" (water-fearing) substances.

• When a substance dissolves in a liquid,When a substance dissolves in a liquid, the the mixture is termed a solution. The dissolved mixture is termed a solution. The dissolved substance (in this case sugar) is the solute, substance (in this case sugar) is the solute, and the liquid that does the dissolving (in and the liquid that does the dissolving (in this case water) is the solvent. this case water) is the solvent.

• Water is a very strong solvent, referred to Water is a very strong solvent, referred to as the universal solvent, dissolving many as the universal solvent, dissolving many types of substances. types of substances.

NaCl

HydrophilicHydrophilicsalts, sugars, acids, salts, sugars, acids, alkalis, and some gasesalkalis, and some gases

HydrophobicHydrophobicfats and oilsfats and oils

3535

• They They dissolve in waterdissolve in water, because , because their molecules separate from their molecules separate from each other, each becoming surrounded by water molecules.each other, each becoming surrounded by water molecules.

3636

pH balancepH balance• Water in a pure state has a Water in a pure state has a

neutral neutral pHpH. As a result, pure . As a result, pure water is neither water is neither acidicacidic nor nor basicbasic. Water changes its pH . Water changes its pH when substances are when substances are dissolved in it. Rain has a dissolved in it. Rain has a naturally acidic pH of about naturally acidic pH of about 5.6 because it contains 5.6 because it contains natural derived carbon natural derived carbon dioxide and sulfur dioxide. dioxide and sulfur dioxide.

The pH of a sample of water is a measure of the concentration of hydrogen ions.

3737

Biochemical reactionsBiochemical reactions• WWater is a regulator of biochemical reactions. All of them start ater is a regulator of biochemical reactions. All of them start

and complete by direct or indirect reaction with the water and complete by direct or indirect reaction with the water molecules in the cell. The speed of the biochemical processes is molecules in the cell. The speed of the biochemical processes is reduced by the reduction of water content under some limitsreduced by the reduction of water content under some limits..

• With tremendous odds against unicellular organisms, they exude With tremendous odds against unicellular organisms, they exude water, as a result of which the cytosol is condensed and the vital water, as a result of which the cytosol is condensed and the vital processes are reduced to a minimum. This state of organisms is processes are reduced to a minimum. This state of organisms is called 'vita minima' or anabiosis. At optimal living conditions the called 'vita minima' or anabiosis. At optimal living conditions the amount of water in the organisms gets back to normal and the amount of water in the organisms gets back to normal and the constitution is restored to its normal active state.constitution is restored to its normal active state.

3838

AfterwordAfterword

• Once the unique role of water in the living systems Once the unique role of water in the living systems was was expressed by a prominent biochemist Szent-Dyerdyi in expressed by a prominent biochemist Szent-Dyerdyi in the phrase: “Water is not only a mother, but a matrix of the phrase: “Water is not only a mother, but a matrix of life”. That is why everybody should take thought life”. That is why everybody should take thought of of it.it.

• Water is closely connected not only with the birth Water is closely connected not only with the birth of of life, but life, but with its evolution as well. It has always been a limiting factor. with its evolution as well. It has always been a limiting factor. The lack of water is one of the main forces controlling the The lack of water is one of the main forces controlling the natural selection. All terrestrial organisms take water and natural selection. All terrestrial organisms take water and preserve it by some means or other. Clear examples can preserve it by some means or other. Clear examples can easily be found among desert ones such as cacti and camels. easily be found among desert ones such as cacti and camels.

3939

4040

Conclusion :Conclusion :• Save water!Save water!• Save life! Save life!

Author: Diana Sofronieva