NAME : UZMA AFRIN AKHTERNAME : UZMA AFRIN AKHTER

CLASS : XCLASS : X

SECTION :BSECTION :B

SUBJECT : SCIENCESUBJECT : SCIENCE

BOARD REGISTRATION BOARD REGISTRATION NO. :B114084140109NO. :B114084140109

ROLL NO. : 52ROLL NO. : 52

CHEMISTRY

HARDNESS OF WATER

• Perhaps you have on occassion Perhaps you have on occassion noticed mineral deposits on your noticed mineral deposits on your

cooking dishes, or rings of cooking dishes, or rings of insoluble soap scum in your insoluble soap scum in your

bathtub. These are not signs of bathtub. These are not signs of poor housekeeping, but are poor housekeeping, but are

rather signs of hard water from rather signs of hard water from the municipal water supply. Hard the municipal water supply. Hard

water is water that contains water is water that contains cations with a charge of +2, cations with a charge of +2, especially Ca2+ and Mg2+. especially Ca2+ and Mg2+. These ions do not pose any These ions do not pose any health threat, but they can health threat, but they can

engage in reactions that leave engage in reactions that leave insoluble mineral deposits. These insoluble mineral deposits. These

deposits can make hard water deposits can make hard water unsuitable for many uses, and so unsuitable for many uses, and so

a variety of means have been a variety of means have been developed to "soften" hard developed to "soften" hard

water; i.e.,remove the calcium water; i.e.,remove the calcium and magnesium ions.and magnesium ions.

• Mineral deposits are formed by ionic reactions Mineral deposits are formed by ionic reactions resulting in the formation of an insoluble precipitate. resulting in the formation of an insoluble precipitate. For example, when hard water is heated, Ca2+ ions For example, when hard water is heated, Ca2+ ions react with bicarbonate (HCO3-) ions to form react with bicarbonate (HCO3-) ions to form insoluble calcium carbonate (CaCO3), as shown in insoluble calcium carbonate (CaCO3), as shown in Equation 1Equation 1

• .This precipitate, known as scale, coats the vessels .This precipitate, known as scale, coats the vessels in which the water is heated, producing the mineral in which the water is heated, producing the mineral deposits on your cooking dishes. In small quantities, deposits on your cooking dishes. In small quantities, these deposits are not harmful, but they may be these deposits are not harmful, but they may be frustrating to try to clean. As these deposits build frustrating to try to clean. As these deposits build up, however, they reduce the efficiency of heat up, however, they reduce the efficiency of heat transfer, so food may not cook as evenly or quickly transfer, so food may not cook as evenly or quickly in pans with large scale deposits. More serious is the in pans with large scale deposits. More serious is the situation in which industrial-sized water boilers situation in which industrial-sized water boilers become coated with scale: the cost in heat-transfer become coated with scale: the cost in heat-transfer efficiency can have a dramatic effect on your power efficiency can have a dramatic effect on your power bill! Furthermore, scale can accumulate on the bill! Furthermore, scale can accumulate on the inside of appliances, such as dishwashers, and inside of appliances, such as dishwashers, and pipes. As scale builds up, water flow is impeded, and pipes. As scale builds up, water flow is impeded, and hence appliance parts and pipes must be replaced hence appliance parts and pipes must be replaced more often than if Ca2+ and Mg2+ ions were not more often than if Ca2+ and Mg2+ ions were not present in the water.present in the water.

• For large-scale municipal operations, a process known as the "lime-soda For large-scale municipal operations, a process known as the "lime-soda process" is used to remove Ca2+ and Mg2+ from the water supply. Ion-process" is used to remove Ca2+ and Mg2+ from the water supply. Ion-exchange reactions, similar to those you performed in this experiment, exchange reactions, similar to those you performed in this experiment, which result in the formation of an insoluble precipitate, are the basis of which result in the formation of an insoluble precipitate, are the basis of this process. The water is treated with a combination of slaked lime, this process. The water is treated with a combination of slaked lime, Ca(OH)2, and soda ash, Na2CO3. Calcium precipitates as CaCO3, and Ca(OH)2, and soda ash, Na2CO3. Calcium precipitates as CaCO3, and magnesium precipitates as Mg(OH)2. These solids can be collected, thus magnesium precipitates as Mg(OH)2. These solids can be collected, thus removing the scale-forming cations from the water supply.removing the scale-forming cations from the water supply.

• To see this process in more detail, let us consider the reaction for the precipitation of To see this process in more detail, let us consider the reaction for the precipitation of Mg(OH)2. Consultation of the solubility guidelines in the experiment reveals that the Mg(OH)2. Consultation of the solubility guidelines in the experiment reveals that the Ca(OH)2 of slaked lime is moderately soluble in water. Hence, it can dissociate in water Ca(OH)2 of slaked lime is moderately soluble in water. Hence, it can dissociate in water to give one Ca2+ ion and two OH- ions for each unit of Ca(OH)2 that dissolves. The OH- to give one Ca2+ ion and two OH- ions for each unit of Ca(OH)2 that dissolves. The OH- ions react with Mg2+ ions in the water to form the insoluble precipitate. The Ca2+ ions ions react with Mg2+ ions in the water to form the insoluble precipitate. The Ca2+ ions are unaffected by this reaction, and so we do not include them in the net ionic reaction are unaffected by this reaction, and so we do not include them in the net ionic reaction (Equation 2). They are removed by the separate reaction with CO32- ions from the soda (Equation 2). They are removed by the separate reaction with CO32- ions from the soda ash.ash.

• Household water softeners typically use a different process, known as ion exchange. Household water softeners typically use a different process, known as ion exchange. Ion-exchange devices consist of a bed of plastic (polymer) beads covalently bound to Ion-exchange devices consist of a bed of plastic (polymer) beads covalently bound to anion groups, such as -COO-. The negative charge of these anions is balanced by Na+ anion groups, such as -COO-. The negative charge of these anions is balanced by Na+ cations attached to them. When water containing Ca2+ and Mg2+ is passed through cations attached to them. When water containing Ca2+ and Mg2+ is passed through the ion exchanger, the Ca2+ and Mg2+ ions are more attracted to the anion groups the ion exchanger, the Ca2+ and Mg2+ ions are more attracted to the anion groups than the Na+ ions. Hence, they replace the Na+ ions on the beads, and so the Na+ than the Na+ ions. Hence, they replace the Na+ ions on the beads, and so the Na+ ions (which do not form scale) go into the water in their place.ions (which do not form scale) go into the water in their place.

• When hard tapwater passes through the ion exchanger (left), the calcium ions from the When hard tapwater passes through the ion exchanger (left), the calcium ions from the tapwater replace the sodium ions in the ion exchanger. The softened water, containing tapwater replace the sodium ions in the ion exchanger. The softened water, containing sodium ions in place of calcium ions, can be collected for household use.sodium ions in place of calcium ions, can be collected for household use.

PHYSICSWATER AS AN

ENERGY RESOURCE

• Water energy Water energy resources include resources include hydroelectric power hydroelectric power from lakes and from lakes and rivers, ocean energy rivers, ocean energy in its various forms, in its various forms, and energy and energy technologies that technologies that take advantage of take advantage of saline watersaline water

• Hydropower makes use of the kinetic Hydropower makes use of the kinetic energy water gains when it drops in energy water gains when it drops in elevation. Typically, water dammed in a elevation. Typically, water dammed in a lake or reservoir is released through lake or reservoir is released through turbines and generators to produce turbines and generators to produce electricity, Hydropower has been a electricity, Hydropower has been a staple of electricity since the beginnings staple of electricity since the beginnings of the electric age. However, very little of the electric age. However, very little of this potential is currently slated for of this potential is currently slated for development. Significant legal and development. Significant legal and regulatory impediments, such as land regulatory impediments, such as land acquisition and environmental acquisition and environmental protection, will be a part of any major protection, will be a part of any major hydro project. Additionally, reservoirs hydro project. Additionally, reservoirs are typically built and managed as are typically built and managed as municipal water supply and flood control municipal water supply and flood control systems and secondarily for power systems and secondarily for power productionproduction. This fact lowers the . This fact lowers the potential impact of hydro development potential impact of hydro development on the energy picture.on the energy picture.

• Three distinct types of ocean resource Three distinct types of ocean resource are commonly mentioned as possible are commonly mentioned as possible energy sources: tides, waves, and energy sources: tides, waves, and ocean temperature differentials (ocean ocean temperature differentials (ocean thermal energy conversion, or OTEC). thermal energy conversion, or OTEC). For example, tidal energy schemes For example, tidal energy schemes capture water at high tide and release capture water at high tide and release it at low tide. Wave energy generation it at low tide. Wave energy generation devices fall into two general devices fall into two general classifications, fixed and floating. In classifications, fixed and floating. In both cases, the oscillating motion of an both cases, the oscillating motion of an incoming and outgoing wave is used to incoming and outgoing wave is used to drive turbines that generate drive turbines that generate electricuty. Tide energy systems traps electricuty. Tide energy systems traps high tides in a reservoir. When the tide high tides in a reservoir. When the tide drops, the water behind the reservoir drops, the water behind the reservoir flows through a power turbine, flows through a power turbine, generating electricity. Ocean thermal generating electricity. Ocean thermal energy conversion uses the difference energy conversion uses the difference in temperature between warm surface in temperature between warm surface water and cold deep ocean water to water and cold deep ocean water to make electricity.make electricity.

• Saline and brackish water is common - Saline and brackish water is common - normally it poses a problem for fresh water normally it poses a problem for fresh water supplies. Several technologies, however, can supplies. Several technologies, however, can take advantage of saline water for energy take advantage of saline water for energy production. These include solar ponds and production. These include solar ponds and algae production. Solar ponds use the salt algae production. Solar ponds use the salt water in such a manner that heat from water in such a manner that heat from sunlight is effectively locked in the pool and sunlight is effectively locked in the pool and can be used for a number of process heat can be used for a number of process heat applications or electricity production. The applications or electricity production. The ability of the pond to store solar thermal ability of the pond to store solar thermal energy is unique and overcomes the resource energy is unique and overcomes the resource variability that is a drawback of traditional variability that is a drawback of traditional solar development. Salt water algaes grow solar development. Salt water algaes grow prolifically under cultivated conditions and prolifically under cultivated conditions and can be pressed to extract biodiesel feedstocks can be pressed to extract biodiesel feedstocks or dried and burned for power production. or dried and burned for power production. Although neither technology has been Although neither technology has been demonstrated beyond pilot levels, Texas is demonstrated beyond pilot levels, Texas is fortunate in that regions with saline water fortunate in that regions with saline water resources also tend to be very sunny. If resources also tend to be very sunny. If coupled with ongoing fresh water chloride coupled with ongoing fresh water chloride control efforts, exploitation of the saline water control efforts, exploitation of the saline water resource for energy production may be resource for energy production may be possible for modest additional investment.possible for modest additional investment.

BIOLOGY

WATER RECYCLING

• Reclaimed water or recycled water, is former Reclaimed water or recycled water, is former wastewater (sewage) that is treated to remove wastewater (sewage) that is treated to remove solids and certain impurities, and used in solids and certain impurities, and used in sustainable landscaping irrigation or to recharge sustainable landscaping irrigation or to recharge groundwater aquifers. The purpose of these groundwater aquifers. The purpose of these processes is sustainability and water processes is sustainability and water conservation, rather than discharging the conservation, rather than discharging the treated water to surface waters such as rivers treated water to surface waters such as rivers and oceans. In some cases, recycled water can and oceans. In some cases, recycled water can be used for streamflow augmentation to benefit be used for streamflow augmentation to benefit ecosystems and improve aesthetics One ecosystems and improve aesthetics One example of this is along Calera Creek in the City example of this is along Calera Creek in the City of Pacifica, CA. of Pacifica, CA.

• The definition of reclaimed water, as defined by The definition of reclaimed water, as defined by Levine and Asaneo, is "The end product of Levine and Asaneo, is "The end product of wastewater reclamation that meets water wastewater reclamation that meets water quality requirements for biodegradable quality requirements for biodegradable materials, suspended matter and pathogens." In materials, suspended matter and pathogens." In more recent conventional use, the term refers more recent conventional use, the term refers to water that is not treated as highly in order to to water that is not treated as highly in order to offer a way to conserve drinking water. This offer a way to conserve drinking water. This water is given to uses such as agriculture and water is given to uses such as agriculture and sundry industry uses.sundry industry uses.

• Cycled repeatedly through the planetary hydrosphere, all water on Earth is recycled water, but the terms "recycled water" or "reclaimed water" typically mean wastewater sent from a home or business through a pipeline system to a treatment facility, where it is treated to a level consistent with its intended use. The water is then routed directly to a recycled water system for uses such as irrigation or industrial cooling.

• The recycling and recharging is often done by using the treated wastewater for designated municipal sustainable gardening irrigation applications. In most locations, it is intended to only be used for nonpotable uses, such as irrigation, dust control, and fire suppression.

• There are examples of communities that have safely used recycled water for many years. Los Angeles County's sanitation districts have provided treated wastewater for landscape irrigation in parks and golf courses since 1929. The first reclaimed water facility in California was built at San Francisco's Golden Gate Park in 1932. The Irvine Ranch Water District (IRWD) was the first water district in California to receive an unrestricted use permit from the state for its recycled water; such a permit means that water can be used for any purpose except drinking. IRWD maintains one of the largest recycled water systems in the nation with more than 400 miles serving more than 4,500 metered connections. The Irvine Ranch Water District and Orange County Water District in Southern California are established leaders in recycled water. Further, the Orange County Water District, located in Orange County, and in other locations throughout the world such as Singapore, water is given more advanced treatments and is used indirectly for drinking.

• 1)Recycle water in your shower. Most people like 1)Recycle water in your shower. Most people like to run the water until it warms up before getting to run the water until it warms up before getting into the shower. Get a bucket to put in your into the shower. Get a bucket to put in your shower and catch the water so that it's not shower and catch the water so that it's not wasted. You can use this water for cooking.wasted. You can use this water for cooking.

• 2)Collect rainwater in order to recycle water. You 2)Collect rainwater in order to recycle water. You can collect it in buckets. Or, you can catch can collect it in buckets. Or, you can catch rainwater from the downspout on your roof rainwater from the downspout on your roof gutters. Attach a water butt to the end of the gutters. Attach a water butt to the end of the gutter or use some other kind of container that gutter or use some other kind of container that will catch the rainwater. You can use this water will catch the rainwater. You can use this water to water your vegetable or flower gardens. It's to water your vegetable or flower gardens. It's good to have in reserve also for watering your good to have in reserve also for watering your shrubs.shrubs.

• 3)Think before you toss the leftover water out of 3)Think before you toss the leftover water out of water glasses. When you and your family drink water glasses. When you and your family drink water, there's often some left in glasses sitting water, there's often some left in glasses sitting around the house. Recycle that water by using it around the house. Recycle that water by using it to water your indoor plants.to water your indoor plants.

• 4)Save the water in your sink after dishwashing. 4)Save the water in your sink after dishwashing. You can use this water to pour into your toilet You can use this water to pour into your toilet bowl tank for flushing. Gather the water in a bowl tank for flushing. Gather the water in a pitcher or pan to transfer it to the bathroom. Of pitcher or pan to transfer it to the bathroom. Of course, you may not want to use the water if it course, you may not want to use the water if it has a lot of grease in it from frying pans. You has a lot of grease in it from frying pans. You don't want greasy water sitting in your toilet don't want greasy water sitting in your toilet tanks.tanks.

Recycled water can be used for almost any use, as long as it is Recycled water can be used for almost any use, as long as it is treated to a level to make it fit for that intended purpose (i.e. treated to a level to make it fit for that intended purpose (i.e. fit-for-purpose) from a health and environmental perspective . fit-for-purpose) from a health and environmental perspective . However, the cost of treatment may make reclamation However, the cost of treatment may make reclamation uneconomical for some uses. Australia now has more than 600 uneconomical for some uses. Australia now has more than 600 different recycled water schemes operating. The bulk of these different recycled water schemes operating. The bulk of these schemes involve:schemes involve:

• Urban and municipal environmentsUrban and municipal environments• Households, golf courses and recreational parks.Households, golf courses and recreational parks.• IndustryIndustry• Washing and cooling in power stations and mills.Washing and cooling in power stations and mills.• AgricultureAgriculture• Horticulture, forestry, pasture, flowers, viticulture and sugar Horticulture, forestry, pasture, flowers, viticulture and sugar

cane.cane.

Other possible uses include:Other possible uses include: • Fire fightingFire fighting• Groundwater rechargeGroundwater recharge• Municipal landscapesMunicipal landscapes• ‘‘Dual pipe’ urban usesDual pipe’ urban uses• Environmental flows and wetlandEnvironmental flows and wetland..