Presentation on the topic of water hardness in chemistry. Presentation on chemistry "water hardness"

Examination work in chemistry on the topic: “Water hardness and ways to eliminate it” Completed by 9th grade student “A” Olin Dmitry Project leader Chemistry teacher Yu.P. Shushlyapina WESTERN DISTRICT DEPARTMENT OF EDUCATION GOU EDUCATION CENTER “SCHOOL OF HEALTH” 1941

Contents of the work: 1. Water is the source of all living things. Water is the source of all living things 2. Determination of water hardness and its negative influence. Determination of water hardness and its negative influence 3. Types of hardness. Types of hardness 4. Methods of eliminating hardness. Methods of eliminating hardness 5 .Equations for eliminating rigidity.Equations for eliminating rigidity 6.Practical part.Practical part 7.Test “Test yourself.”Test “Test yourself” 8.Materials used.Materials used

Water is the source of all living things. Water plays a unique role as a substance that determines the possibility of existence and the very life of all creatures on Earth. It acts as a universal solvent in which the basic biochemical processes of living organisms occur.

Hardness of water. Water hardness is a property of water caused by the presence of soluble calcium and magnesium salts in it. Water Soft Hard less than 2 mmol/l Medium hardness High hardness mmol/l more than 10 mmol/l

Methods for eliminating rigidity. Domestic: 1. Boiling and freezing Boiling and freezing 2. Filtration Filtration 3. Adding softeners Adding softeners Industrial: 1. Adding soda ash Na 2 CO 3 Adding soda ash Na 2 CO 3 2. Adding slaked lime Ca (OH) 2 Adding slaked lime Ca (OH) 2

Practical part. Practical work: “Eliminating the hardness of various types of water.” Purpose of work: 1. Determine the hardness of different types of water. 2.Learn how to eliminate hardness using soda. Equipment and reagents: 1. Test tubes, beaker 2. Soda solution Na 2 CO 3. 3. Digital camera.

Practical part Progress of work: In my practical work, I investigated the hardness of natural water: “Holy Spring”, spring water of the “Matveevskoye” microdistrict, “Narzan” mineral water and tap water. To eliminate hardness, you can use a solution of Na 2 CO 3 soda. I poured the solution into four test tubes and watched what happened.

Practical part. Conclusion: Mineral water "Narzan" and spring water of the microdistrict "Matveevskoye" have greater hardness, that is, they contain the largest amount of magnesium and calcium salts. These types of water are most suitable for drinking, as they provide the body with calcium and magnesium salts, but are not suitable for household purposes.

Question2 Which property does hard water NOT exhibit? 1. Conducts electric current well. Conducts electric current well. 2. Conducts heat well. Conducts heat well. 3. Forms scale when boiled. Forms scale when boiled. 4. Poorly dissolves soap (soap does not foam well) Poorly dissolves soap (soap does not foam well)

Materials used. 1. “Chemistry.” Schoolchildren's Handbook" - Moscow Special thanks to chemistry teacher Yu.P. Shushlyapina for her help.

• Types of water hardness
• Industrial methods for removing water hardness
• The influence of water hardness on human life and health
• The influence of water hardness on domestic and industrial systems
• Bibliography

1. Hardness of water

• 1. Hardness of water from a chemical point of view - a set of physical processes in water associated with the content of dissolved alkaline earth metal salts in it, mainly calcium and magnesium, the so-called “hardness salts”.

Presence of Ca ions 2+ And Mg 2+

2. Water hardness indicators

• White flakes in water Film on tea
• White flakes in water Scale and lime deposits on household appliances Film on tea
• White flakes in water
• Scale and lime deposits on household appliances
• Film on tea

Formation of water hardness in nature

The groundwater – underground deposits of limestone, gypsum, dolomite, water hardness.

Surface water – seasonal variations.

Sea and ocean water – high rigidity.

Fresh natural reservoirs – minimum severity during flood periods.

Types of water hardness.

almost completely eliminated

when boiling water, so

called temporary rigidity.

calcium and magnesium salts are not eliminated by boiling

(constant hardness).

Elimination of temporary rigidity

I. Thermal softening . (By boiling water.)

• I. Thermal softening . (By boiling water.)

Ca(HCO 3 ) 2 = CaCO 3 ↓ + CO 2 +H 2 O .

II. Reagent softening.

• II. Reagent softening.

1.

• 1. Adding soda ash.
• 1. Adding soda ash.

Ca(HCO 3 ) 2 +Na 2 CO 3 = CaCO 3 ↓ + 2NaHCO 3 .

2. Adding slaked lime.

• 2. Adding slaked lime.
• 2. Adding slaked lime.

Ca(HCO 3 ) 2 +Ca(OH) 2 = 2CaCO 3 ↓ + 2H 2 O.

Eliminate Permanent Stiffness

• Reagent softening
• Reagent softening . (By adding soda ash.)

• CaCl 2 +Na 2 CO 3 = CaCO 3 ↓ + 2NaCl.
• CaCl 2 +Na 2 CO 3 = CaCO 3 ↓ + 2NaCl.
• CaCl 2 +Na 2 CO 3 = CaCO 3 ↓ + 2NaCl.

• 2MgSO 4 + 2Na 2 CO 3 +H 2 O== 2 CO 3 ↓ + CO 2 + 2Na 2 SO 4 .
• 2MgSO 4 + 2Na 2 CO 3 +H 2 O== 2 CO 3 ↓ + CO 2 + 2Na 2 SO 4 .
• 2MgSO 4 + 2Na 2 CO 3 +H 2 O== 2 CO 3 ↓ + CO 2 + 2Na 2 SO 4 .

The problem of split ends

hair

The influence of water hardness on household and industrial systems

For modern household appliances,

autonomous hot water supply and heating systems,

the latest models of plumbing water hardness –

catastrophe!

Bibliography:

1 . Ivanov, Geva Chemistry in formulas. Bustard 2004.

2. Lurie Yu.Yu. Handbook of Analytical Chemistry, 1962.

3. Dritsa E.M. Properties of the element. Directory. M.: Metallurgy, 1985.

4. Kogan B.I.. Rare metals. M.: Nauka, 1979.

5. Busev A.I. Definitions, concepts, terms in chemistry. M.: Education, 1981.

6. Nikolsky B.P. Chemist's Handbook. T-2. M.: Chemistry, 1964.

7. Nekrasov B.V. Fundamentals of general chemistry. M.: Chemistry, 1967.

8. Ya.A. Ugai. Inorganic chemistry. M.: Higher School, 1989.

9. Petryanov-Sokolov I.V., Chernenko M.B., Stanzo V.V.

Popular library of chemical elements. M.: Nauka, 1972.

10. Ripan R., Ceteanu I. Inorganic chemistry. M.: Mir, 1971.

Water hardness and ways to eliminate it Rakhimova M., Niskovskaya V. 9 D

Water-chemical
substance in the form
clear liquid, not
having colors
smell and taste. About 71%
the Earth's surface is covered
water.
By features
origin, composition or
applications, highlight
several types of water:
soft and hard water,
mineral water,
distilled water…
Water
Soft
less than 2
mmol/l
Tough
Average
rigidity
High
rigidity
2 - 10
mmol/l
more than 10
mmol/l

Water hardness is caused by the high content of salts dissolved in it.
alkaline earth metals, such as calcium and magnesium. This is the reason
breakdowns of household appliances, mainly washing machines. Get rid of it
properties of water can be studied in different ways.
Drinking hard or soft water poses minor health risks. At
high salt content can form urinary stones, and low levels
does not significantly increase the risk of cardiovascular disease. Taste
spring water is determined precisely by its hardness.

Hard and soft water
The hardness and softness of water depends on the level of salt content in it. In the pen
in the second case it is high, in the second case it is insignificant. These terms appeared
presumably because of the properties that water had on things. If
wash them in hard water, then the fabric itself will be the same. If soft, then
clothes became so.
Water hardness can be temporary or permanent. The first contains
magnesium and calcium bicarbonate, the second - other salts. These are mainly sulfates and
chlorides of the same components. They are released when water boils.

Ways to eliminate water hardness:
Calcium and magnesium salts are dissolved in natural water. These are bicarbonates and sulfates.
1.The first method is boiling. When boiled, soluble bicarbonates pass
into insoluble carbonates, and water hardness decreases.
Сa(HCO3)2 = CaCO3 ↓ + H2O + CO2
2.The second method is to add lime water. When adding lime water
hydrocarbonates turn into carbonates and the water becomes softer.
Сa(HCO3)2+ Ca(OH)2 = CaCO3 ↓ +2 H2O
3.But water hardness also depends on calcium and magnesium sulfates. Calcium sulfates and
magnesium can be removed using sodium carbonate. When adding sodium carbonate
sulfates turn into insoluble calcium and magnesium carbonates.
CaSO4 + Na2CO3= CaCO3 ↓+ Na2SO4

4. Adding softeners. The reduction in overall hardness reaches 100%. Softeners
designed to reduce the overall water hardness in washing machines. Water
cannot be used for cooking, cannot be drunk.
5.Filtration. Filtration reduces overall hardness by up to 80%. Inside the cartridge
The filter contains a mixture of activated carbon and cation exchangers. Coal
adsorbs harmful organic substances and chlorides. Cation exchangers
reduce overall stiffness.
Now we know how to reduce water hardness. The scale inside the kettle is sediment
calcium and magnesium carbonates with an admixture of calcium sulfate. Scale can be removed
from the walls using a dilute solution of acetic acid.

Introduction Introduction In caves, speleologists encounter the most beautiful limestone formations - stalactites hanging from the arches and stalagmites growing upward. From a chemical point of view, the emergence of these amazing creations of nature is the hardness of groundwater. In caves, speleologists encounter the most beautiful limestone formations - stalactites hanging from the arches and stalagmites growing upward. From a chemical point of view, the emergence of these amazing creations of nature is the hardness of groundwater.

How “hard” is hard water? How “hard” is hard water? Water hardness is its property associated with the content of soluble calcium and magnesium compounds in it; it is a parameter showing the content of calcium and magnesium cations in water. Scale on the walls of heating boilers, salt deposits on household appliances, etc. - all these are indicators of hard water. Hard water is not suitable for washing. Scale on the heaters of washing machines disables them; Ca2+ and Mg2+ cations react with fatty acids in soap, forming poorly soluble salts that create films and sediments, ultimately reducing the quality of washing. The relationship between water hardness and the formation of kidney stones is now known. According to current standards, the hardness of drinking water should not exceed 7 mEq/l. There are two types of rigidity: temporary and permanent. With a high content of magnesium ions, water tastes bitter and has a laxative effect on the intestines. There are carbonate and non-carbonate hardness. Carbonate hardness is caused by the presence of dissolved calcium bicarbonates Ca(HCO3)2 and magnesium Mg(HCO3)2. When boiling, bicarbonates are destroyed with the formation of sediments of poorly soluble carbonates CaCO3, the hardness decreases, which is why carbonate hardness is called temporary. When boiling, Mg2+ and Ca2+ ions precipitate in the form of carbonates. The hardness that remains after boiling water is called permanent or non-carbonate. It is caused by calcium and magnesium salts of strong acids (sulfates and chlorides) dissolved in water.

The influence of water hardness on human health Increased water hardness negatively affects human health when washing. Hardness salts interact with detergents and form insoluble slags. These wastes dry out and remain in the form of a microscopic crust on the human skin and hair. The natural fatty film of the human skin and hair is destroyed, pores become clogged, dryness, flaking, and dandruff appear. A sign of increased water hardness is the creaking of cleanly washed skin and hair. A feeling of increased soapiness, a sign that the protective film on the skin is intact and the water hardness is low. Therefore, cosmetologists advise washing your face with rain or melt water. From the point of view of the use of water for drinking purposes, its acceptability in terms of hardness can vary significantly depending on local conditions. High hardness worsens the organoleptic properties of water, giving it a bitter taste and having a negative effect on the digestive organs. In addition, when hard salts interact with detergents, “soap slag” is formed in the form of foam; after drying, it remains as a deposit on plumbing fixtures, linen, human skin, and hair.

Chemistry of water hardness Sediment and scale (hardness salts) are formed as a result of the interaction of cations with anions. The table below shows the main metal anions and cation exchangers with which they associate and cause hardness. Iron, manganese and strontium have little effect on hardness compared to calcium and magnesium. The solubility of Aluminum and ferric Iron is low at the pH level of natural water, so their effect on water hardness is also small. CationsAnions Magnesium (Mg2+) Sulfate (SO42-) Calcium (Ca2+) Bicarbonate (HCO3-) Iron (Fe2+) Nitrate (NO3-) Strontium (Sr2+) Chloride (Cl-) Manganese (Mn2+) Silicate (SiO32-)

Occurrence of Hardness Calcium and magnesium ions, as well as other alkaline earth metals that determine hardness, are present in all mineralized waters. They are formed by deposits of limestone and gypsum. Calcium and magnesium ions enter the water during the processes of dissolution and chemical weathering of rocks. Ions are formed during microbiological processes occurring in the ground, where water is discharged in bottom sediments. As a rule, in low-mineralized waters, hardness due to ions predominates. With increasing mineralization of water, the content of calcium ions rapidly decreases. The amount of magnesium ions in highly mineralized waters can reach several grams, and in salt lakes - tens of grams per liter of water. Usually the hardness of groundwater is higher than the hardness of surface water. The hardness of surface water fluctuates depending on the season, usually reaching its highest value at the end of winter and the lowest during the flood period, when it is abundantly diluted with soft rain and melt water. Sea and ocean water have very high hardness.

Water softening Water softening is the process of reducing water hardness, i.e. decrease in the concentration of calcium and magnesium ions. Hard water negatively affects human health and the operation of plumbing and boiler equipment. Therefore, in order not to damage the equipment, water softening is required. With increased water hardness in boilers and boilers, water softening is necessary. Several methods of water softening are used, which are selected based on factors: Depth of water softening Quality of source water Economic considerations

Water softening methods: Reagent water softening, with this method of water purification, Ca+2 and Mg+2 ions are bound by various substances into insoluble compounds. Electromagnetic effects on water. This method of water purification does not reduce its hardness, but prevents the formation of scale and carbonate deposits. This method is used where water softening is not an end in itself. Read more about the chemistry of water hardness. To get rid of temporary hardness, you just need to boil water. When water is boiled, bicarbonate anions react with cations and form very slightly soluble carbonate salts with them, which precipitate. Ca2 + 2HCO3- = CaCO3v + H2O + CO2^ Constant hardness is more difficult to combat. One option: freezing ice. You just need to gradually freeze the water. When approximately 10% of the liquid remains of the original amount, it is necessary to drain the frozen water and turn the ice back into water. All salts that form hardness remain in unfrozen water. One way is to evaporate water followed by condensation. Since salts are non-volatile compounds, they remain and the water evaporates. But methods such as freezing and distillation are only suitable for softening small amounts of water. From a chemical point of view, the consequence of water hardness - scale - can be dealt with very simply. It is necessary to act on the salt of a weak acid with a stronger acid.

12 About the iron content in drinking water High iron content in water causes sedimentation in pipes and their overgrowing, and also worsens the taste of drinking water (there is a taste of rust), and “iron” water leaves yellow stains on plumbing fixtures and stains on clothes. Iron is almost always found in surface and groundwater well waters. Also, due to corrosion of pipes, rust gets into drinking water. Iron compounds in water are present in dissolved and undissolved forms. 1. To remove rust, so-called “mechanical” filters are used. The filter elements are presented in the form of a washable stainless steel mesh; quartz sand and ceramic chips are also used. 2. Dissolved iron comes in trivalent and divalent forms. The trivalent form is a yellow solution, the divalent form is a colorless solution. In the presence of oxygen in water, divalent iron very quickly transforms into the trivalent form and forms slightly soluble iron hydroxide. 4Fe 2+ + O2 + 2H2O = 4Fe(OH)3 During aeration, divalent iron is oxidized into the trivalent form according to the following overall reaction: 4Fe2+ + O2 +10H2O = 4Fe (OH) 3 + 8H+ Also, instead of air oxygen, to convert Fe2+ to Fe3+, you can use other oxidizing agents, for example, potassium permanganate. These methods purify water from manganese (Mn2+), which often accompanies divalent iron: 3Fe (HCO3)3 + KMnO3 + 2H2O = 3Fe (OH)3 + MnO2 + 5CO2 + KHCO3 In the case of divalent manganese, the following oxidation reaction occurs: 3Mn2+ + 2MnO4 - + 2H2O = 5MnO2 + 4H+

Results of student research Study of water hardness in Novy Oskol p/p Study water Water hardness Type of water 1 Snow water 0.8 Very soft 2 Tap water 5.6 Medium hardness 3 Water from a tap 7.1 Medium hardness 4 Water from a well (Pokrovskaya St.) 11.64 Very hard 5 Bottled water 6 Medium hardness 6 Water with added milk 9.6Hard

The city of Lomonosov is supplied with water from underground sources of the Ordovician aquifer, which consists of durable limestones and dolomites. This horizon is used most intensively where it lies close to the surface - within the Izhora (Silurian) plateau. As water seeps through, it dissolves the rocks through which it flows and absorbs these substances. Water from underground sources in the Leningrad region is quite hard. Hardness is one of the main indicators of drinking water quality. The purpose of our work is to determine the hardness of drinking and natural water using the titrimetric method (direct complexometric titration). To achieve this, the following tasks were set: 1. To become familiar with the titrimetric (complexometric) method. 2. Get acquainted with water quality indicators and their definition, with the classification of water according to the method of its use. 3. Study the parameters of the quality and purity of drinking water. 4. Compare the hardness indicators of natural and drinking water taken from different sources. 5. Compare water hardness indicators when softening it in everyday life using various methods. 6. Give recommendations to students of GBOU school No. 430 of the Petrodvorets district on eliminating water hardness at home.