DIGITAL TEXT Basic Science Standard-8

Vaisakh S Physical Science 2021-2023

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National Anthem Jana Gana Mana Adhinayaka Jay He Bharata Bhagya Vidhata Panjab Sindhu Gujarat Maratha Dravida Utkala Banga Vindhya Himachal Yamuna Ganga Uchchala Jaladhi Taranga Tava Subha Name Jaage Tave Subha Aashish Mange Gaahe Tava Jay Gaatha Jana Gana Mangal Daayak Jay He Bharat Bhagya Vidhata Jay he Jay he Jay he Jay Jay Jay Jay He

Pledge India is my country. All Indians are my brothers and sisters. I love my country, and I am proud of its rich and varied heritage. I shall always strive to be worthy of it. I shall give my parents, teachers and all elders respect, and treat everyone with courtesy. To my country and my people, I pledge my devotion. In their wellbeing and prosperity alone lies my happiness 2

Dear students, You have the opportunity to explore the surroundings through the magic of science especially chemistry. One of the major branches in science which include many interesting concepts and experiments that help you to increase the capability of your observation skill, problem solving skill, thinking skills etc. Moreover a science text book is a source of wide variety of knowledge that is very essential for an individual who have been living in the society. Go ahead, thinking, asking questions, approaching ideas critically and quizzing with teachers and friends. Enjoy the topic.Make learning a joyful experience. Regards, Vaisakh S

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CONSTITUTION OF INDIA Part IV A FUNDAMENTAL DUTIES OF CITIZENS ARTICLE 51 A

Fundamental Duties- It shall be the duty of every citizen of India: (a) to abide by the Constitution and respect its ideals and institutions, the National Flag and the National Anthem; (b) to cherish and follow the noble ideals which inspired our national struggle for freedom; (c) to uphold and protect the sovereignty, unity and integrity of India; (d) to defend the country and render national service when called upon to do so; (e) to promote harmony and the spirit of common brotherhood amongst all the people of India transcending religious, linguistic and regional or sectional diversities; to renounce practices derogatory to the dignity of women; (f) to value and preserve the rich heritage of our composite culture; (g) to protect and improve the natural environment including forests, lakes, rivers, wild life and to have compassion for living creatures; (h) to develop the scientific temper, humanism and the spirit of inquiry and reform; (i) to safeguard public property and to abjure violence; (j) to strive towards excellence in all spheres of individual and collective activity so that the nation constantly rises to higher levels of endeavour and achievements; (k) who is a parent or guardian to provide opportunities for education to his child or, as the case may be, ward between age of six and fourteen years.

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Water Structure of water………………………………………………………...9 Three Forms of Water……………………………………………………10 Boiling Point of Water…………………………………………………...11 Heat Capacity of Water…………………………………………………..13 Anomalous Expansion of water………………………………………….15 Freezing Point of Water…………………………...……………………...16 Surface Tension of Water………………………………………...………17 Water-Universal Solvent………………………………………………....20 Soft water and Hard Water………………………………………………..22 Dissolved Oxygen and Aquatic Life……………………………………...28 Water Pollution…………………………………………………………..29

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Water,a

substance

composed

of

the chemical

elements hydrogen and oxygen and

existing

in

gaseous, liquid, and solid states. It is one of the most plentiful and essential of compounds. A tasteless and odourless liquid at room temperature, it has the important ability to dissolve many other substances. Indeed, the versatility of water as a solvent is essential to living organisms. Life is believed to have originated in the aqueous solutions of the world’s oceans, and living organisms depend on aqueous solutions, such as blood and digestive juices, for biological processes. Water also exists on other planets and moons both within and beyond the solar system. In small quantities water appears colourless, but water actually has an intrinsic blue

colour

caused

by

slight

absorption

of light at

red

wavelengths. Water occurs as a liquid on the surface of Earth under normal conditions, which makes it invaluable for transportation, for recreation, and as a habitat for a myriad of plants and animals. The fact that water is readily changed to a

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vapour (gas) allows it to be transported through the atmosphere from the oceans to in land areas where it condenses and, as rain, nourishes plant and animal life. Because of its prominence, water has long played an important religious and philosophical role in human history. In the 6th century BCE, Thales of Miletus, sometimes credited for initiating Greek philosophy, regarded water as the sole fundamental building block of matter: Two hundred years later, Aristotle considered water to be one of four fundamental elements, in addition to earth, air, and fire. The belief that water was a fundamental substance persisted for more than 2,000 years until experiments in the second half of the 18th century showed that water is a compound made up of the elements hydrogen and oxygen.The water on the surface of Earth is found mainly in its oceans (97.25 percent) and polar ice caps and glaciers (2.05 percent), with the balance in freshwater lakes, rivers, and groundwater.

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Structure of Water The molecules of water are simple in structure,the physical and chemical properties of the compound are extraordinarily complicated, and they are not typical of most substances found on Earth.The water molecule is composed of two hydrogen atoms,

each

linked

by

a

single chemical

bond to

an oxygen atom.The chemical formula of water is H₂O.The volume of hydrogen and oxygen atoms in the water molecule is in the ratio 2:1

Ball and Stick Model of Water

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Three forms of Water

Solid

Liquid

Gas

Water can occur in three states: solid (ice), liquid, or gas (vapor). Solid water—ice is frozen water. When water freezes, its molecules move farther apart, making ice less dense than water. This means that ice will be lighter than the same volume of water, and so ice will float in water. Water freezes at 0° Celsius, 32° Fahrenheit. Liquid water is wet and fluid. This is the form of water with which we are most familiar. We use liquid water in many ways, including washing and drinking.

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Water as a gas—vapor is always present in the air around us. You cannot see it. When you boil water, the water changes from a liquid to a gas or water vapor. As some of the water vapor cools, we see it as a small cloud called steam. This cloud of steam is a mini version of the clouds we see in the sky. At sea level, steam is formed at 100° Celsius, 212° Fahrenheit.

Properties of Water Boiling Point boiling point, temperature at which the pressure exerted by the surroundings upon a liquid is equaled by the pressure exerted by the vapour of the liquid; under this condition, addition of heat results in the transformation of the liquid into its vapour without raising the temperature. At any temperature a liquid partly vaporizes into the space above it until the pressure exerted by the vapour reaches a characteristic value called the vapour pressure of the liquid at that temperature. As the temperature is increased, the 11

vapour pressure increases; at the boiling point, bubbles of vapour form within the liquid and rise to the surface. The boiling point of a liquid varies according to the applied pressure; the normal boiling point is the temperature at which the vapour pressure is equal to the standard sea-level atmospheric pressure (760 mm [29.92 inches] of mercury). At sea level, water boils at 100° C (212° F). At higher altitudes the temperature of the boiling point is lower.

It is easy to prepare food in pressure cookers. Do you know why? The boiling point of water increases with an increase in the pressure. In pressure cookers, water boils at 120o C. Hence, high temperature exists inside the cooker.But in lower altitude water boils at low temperature that is atmospheric pressure is directly proportional to boiling point. Water exists in the liquid form at temperatures between 0°C and 100°C. But water changes to vapour at any temperature upto 100°C. Evaporation is the process by which a liquid changes to vapour. On heating water, the heat

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absorbed is utilised for rise in temperature and for evaporation.

Heat Capacity The high specific heat of water has a great deal to do with regulating extremes in the environment. For instance, the fish in this pond are happy because the specific heat of the water in the pond means the temperature of the water will stay relatively the same from day to night. They don't have to worry about either

turning

on

the

air

conditioner or putting on their woolen flipper gloves. Lucky for me, you, and the fish in the pond to the right, water has a higher specific heat than many other substances. One of water's most significant properties is that it takes a lot of energy to heat it. Precisely, water has to absorb 4,184 Joules of heat (1 kilocalorie) for the temperature of one kilogram

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of water to increase 1°C. For comparison sake, it only takes 385 Joules of heat to raise 1 kilogram of copper 1°C. The following are some of the situations which make use of the high heat capacity of water.

 Water is used in radiators to regulate the heat in automobile engines.  Water is used to cool hot objects.  Two thirds of the earth is water. This regulates the temperature of the earth.

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Anomalous expansion of water

When water is cooled, its density increases and the cold water goes down. This occurs till the temperature reaches 4°C. When atmospheric temperature goes below 4°C, due to anomalous expansion of water its volume increases while its density decreases. Water below 4°C rises to the surface. It freezes and covers the surface of water with ice which is less dense than water.

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Aquatic life in water bodies at colder regions is sustained in the water below this layer of ice.

Freezing point

The freezing point describes the liquid to solid transition while the melting point is the temperature at which water goes from a solid (ice) to liquid water. Freezing point of a liquid is the temperature at which it freezes to solid at normal atmospheric pressure. The freezing point of water is 0oC In theory, the two temperatures would be the same, but liquids can be supercooled beyond their freezing points so that they don't solidify until well below freezing point. 16

Ordinarily, the freezing point of water and melting point is 0 °C or 32 °F. The temperature may be lower if supercooling occurs or if there are impurities present in the water which could cause freezing point depression to occur. Under certain conditions, water may remain a liquid as cold as -40 to -42°F! When water is converted to ice its volume increases and the density decreases.

Surface tension Surface

tension is

the

tendency

of liquid surfaces at rest to shrink into the minimum surface

area possible.

Surface tension is what allows objects with a higher density than water such as razor blades and insects (e.g. water striders) to float on a water surface without becoming even partly submerged.

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At liquid–air interfaces, surface tension results from the greater attraction of liquid molecules to each other (due to cohesion) than to the molecules in the air (due to adhesion). There are two primary mechanisms in play. One is an inward force on the surface molecules causing the liquid to contract. Second is a tangential force parallel to the surface of the liquid. This tangential force is generally referred to as the surface tension. The net effect is the liquid behaves as if its surface were covered with a stretched elastic membrane. But this analogy must not be taken too far as the tension in an elastic membrane is dependent on the amount of deformation of the membrane while surface tension is an inherent property of the liquid–air or liquid– vapour interface. Because

of

the

relatively

high

attraction of water molecules to each

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other through a web of hydrogen bonds, water has a higher surface tension (72.8 millinewtons (mN) per meter at 20 °C) than most other liquids. Surface tension is an important factor in the phenomenon of capillarity. Surface tension has the dimension of force per unit length, or of energy per unit area. The two are equivalent, but when referring to energy per unit of area, it is common to use the term surface energy, which is a more general term in the sense that it applies also to solids.In materials science, surface tension is used for either surface stress or surface energy. Surface tension acts in such a way so as to reduce the surface area of a liquid. For the definite mass of a substance, surface area is minimum for spherical shape. That is why liquid droplets assume spherical shape.

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Water-Universal Solvent

Water is a ―universal solvent‖ because no other liquid can dissolve any substance to the extent that it does. Life is incomplete without water as animals and plants cannot survive without water. When water mixes with air, the ground, or our bodies, it usually takes along all kinds of valuable minerals, nutrients, and chemicals. Water acts as an excellent solvent universally due to its chemical compositions and physical attributes. The polar arrangement of oxygen and 20

hydrogen in water molecules is in such a way that on one side, oxygen has a negative charge, and on the other, hydrogen has a positive electrical charge. This is the main reason why other molecules are attracted to water molecules. When substances dissolve in water they acquire the property of the substance dissolved. Pure water has neither the properties of acid nor those of alkali. Hence it is called neutral solvent. Since water can dissolve various substances and is widely used for preparing solutions, it is a universal solvent

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Soft water and hard water

You may have heard water referred to as being either hard or soft, but what does that really mean? The mineral content of water affects how it is classified on a scale ranging from hard to soft. All water is not created equal. Around 85% of the US water supply is hard, but many businesses and homeowners utilize water softeners to strip away extra minerals. But which one is better for you, hard water or soft water?

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The water in which soap does not lather easily is called hard water. Here, the hardness of water is due to the presence of dissolved salts of calcium and magnesium. Water in which soap gives lather readily is called soft water. The hardness of water containing Calcium or Magnesium bicarbonates is removed during boiling. This type of hardness of water is known as temporary hardness. The hardness of water containing the chlorides and sulphates of calcium and magnesium is not removed even after boiling. This is permanent hardness Permanent hardness of water can be removed only by using certain chemicals. The temporary hardness of water is removed during boiling of water. This is due to the decomposition of bicarbonates during heating. But permanent hardness cannot be removed like this The hardness or softness of water is determined by the mineral content of both calcium and magnesium 

Soft water has less than 17 parts per million



Slightly hard water has 17 to 60 parts per million 23



Moderately hard water has 60 to 120 parts per million



Hard water has 120 to 180 parts per million



Very hard water has greater than 180 parts per million

Risks and Benefits of Hard Water and Soft Water Both types of water offer unique risks and benefits, and water quality may vary for both hard and soft water. It usually comes down to personal preference and what you’re using the water for. There is a lot of information out there about hard and soft water, but some of it is just myths or misunderstandings. Understanding contamination. Hard water contains more minerals, but that doesn’t mean it’s contaminated. Contamination is different than mineral content and refers to germs and bacteria instead. Minerals are valuable nutrients for your body, although too many may pose health risks. Clogged pipes. Some people believe that hard water can clog the pipes in your home. A long time ago, when homes were built using galvanized steel, 24

excessive levels of magnesium and calcium did stick to the inside of the pipes. So if you have an older home built from the mid-1940s to the mid-1970s, this may be a cause for concern. Otherwise, it’s not something you need to worry about. Water taste. Interestingly enough, hard water is thought to taste worse because of its higher mineral content. In reality, softer water is more likely to taste different than what you’re used to. Minerals improve water’s taste, while softer water lacks these taste differentiators. If your water is softened using a chemical or filtration system, it may taste slightly salty. Soft water is better. Many people believe that soft water offers a better clean for your body and your home because it doesn’t leave behind a mineral residue like hard water can. But the truth is that neither type of water offers a better or worse clean. However, soft water may leave you feeling like there’s a residue because the lack of minerals makes skin feel slippery.

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Rainwater is hard. Water that falls from the sky starts out soft because it cannot carry as many minerals during evaporation. However, as it flows along the ground, it picks up minerals along the way. Mineral intake. Most of the time, added minerals are good for your body. However, in some cases they may pose health risks. Too much magnesium may lead to renal issues and diarrhea, similar to a laxative effect.

Treating Hard Water If you’re concerned that your water is too hard, there are several options for softening it. Keep in mind that water softeners are not water filters and don’t usually remove any contaminants from your water. Ion exchange. This technology uses a physical and chemical process to filter your water through resin or zeolite. Positively charged sodium ions attract calcium and magnesium, removing it from your water. Eventually, the resin in an ion filter reaches its maximum capacity and stops working. Using a reverse flush technique, you can rinse the brine from inside the filter to continue using it effectively. 26

Choosing a model. You can choose a timed water softener that is programmable to filter water during certain times of the day and regenerate during other times. Alternately, you can choose a model that requires manual operation for switching between the two modes. Maintaining your softener. Don’t assume that your water softener is always working correctly. Each model requires regular maintenance to monitor clogs and clean the filtering mechanism. This is also important since bacteria and fungi may accumulate in the filter over time and need removal.

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Dissolved Oxygen and Aquatic Life

Dissolved oxygen (DO) is essential to all aquatic life. While humans and terrestrial animals breathe oxygen from the air, aquatic animals use oxygen that is dissolved in water. An aquatic animal breathes by absorbing free oxygen into its blood through its gills or directly through its body surface. Oxygen (O2) is consumed in surface waters by all aquatic organisms: fish, plants, algae, bacteria, and invertebrates. The oxygen molecule in dissolved oxygen is free (O2) which differs from the oxygen atom bound to hydrogen in

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a water molecule (H2O). Oxygen gets into water three ways: 1) diffusion from the surrounding air; 2) aeration (rapid movement); and 3) when released as a by-product of photosynthesis by algae and aquatic plants. There are a number of physical and biological factors that can impact the DO levels in water body such as a lake which are temperature, decomposition, photosynthesis

Water Pollution Water pollution (or aquatic pollution) is the contamination of water bodies, usually as a result of human activities, so that it negatively affects its uses.Water

bodies

include lakes, rivers, oceans, aquifers , reservoirs and groundwater. Water pollution results when contaminants mix with these water

bodies.

come

from

Contaminants one

of

four

can main

sources: sewage discharges, industrial activities, agricultural activities, and urban runoff including storm water. Water pollution is either surface 29

water pollution or groundwater pollution. This form of pollution can lead to many

problems,

such

as

the degradation of aquatic

ecosystems or

spreading water-born environmental diseases when people use polluted water for drinking or irrigation. Another problem is that water pollution reduces the ecosystem services (such as providing drinking water) that the water resource would otherwise provide. Sources of water pollution are either point sources or non-point sources. Point sources have one identifiable cause, such as a storm drain, a wastewater treatment plant or an oil spill. Non-point sources are more diffuse, such as agricultural runoff. Pollution is the result of the cumulative effect over time. Pollution may take the form of toxic substances (e.g., oil, metals, plastics, pesticides, persistent organic pollutants, industrial waste products), stressful conditions (e.g., changes of pH, hypoxia or temperatures,

anoxia,

increased

excessive turbidity,

changes of salinity), or the introduction of pathogenic organisms. Contaminants

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may include organic and inorganic substances. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers.

Types of surface water pollution Surface water pollution includes pollution of rivers, lakes and oceans. A subset of surface water pollution is marine pollution which affects the oceans. Nutrient pollution refers to contamination by excessive inputs of nutrients. Globally, about 4.5 billion people do not have safely managed sanitation as of 2017, according to an estimate by the Joint Monitoring Programme for Water Supply and Sanitation. Lack of access to sanitation is concerning and often leads to water pollution, e.g. via the practice of open defecation: during rain events or floods, the human feces are moved from the ground where they were deposited into surface waters. Simple pit latrines may also get flooded during rain events.

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As of 2022, Europe and Central Asia account for around 16% of global microplastics discharge into the seas

Marine pollution

Marine pollution occurs when substances used or spread by humans, such as industrial, agricultural and residential waste, particles, noise, excess carbon dioxide or invasive organisms enter the ocean and cause harmful effects there. The majority of this waste (80%) comes from land-based activity, although marine transportation significantly contributes as well.Since most inputs come from land, either via the rivers, sewage or the atmosphere, it means that continental shelves are more vulnerable to pollution. 32

Nutrient pollution

Nutrient pollution, a form of water pollution, refers to contamination by excessive inputs of nutrients. It is a primary cause of eutrophication of surface waters (lakes, rivers and coastal waters), in which excess nutrients, usually nitrogen or phosphorus, stimulate algal growth. Sources of nutrient pollution include surface runoff from farm fields and pastures, discharges from septic tanks and feedlots, and emissions from combustion.

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Thermal pollution

Thermal pollution, sometimes called "thermal enrichment", is the degradation of water quality by any process that changes ambient water temperature. Thermal pollution is the rise or fall in the temperature of a natural body of water caused by human influence. Thermal pollution, unlike chemical pollution, results in a change in the physical properties of water. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers.[43] Urban runoff—stormwater discharged to surface waters from rooftops, roads and parking lots—and reservoirs can also be a source of thermal pollution.[44] Thermal pollution can also be caused by the release of very cold water from the base of reservoirs into warmer rivers. 34

Groundwater pollution Groundwater pollution (also called groundwater contamination) occurs when pollutants are

released

to

the

ground

and

make

their

way

into groundwater. This type of water pollution can also occur naturally due to the presence of a minor and unwanted constituent, contaminant, or impurity in the

groundwater,

in

which

case

it

is

more

likely

referred

to

as contamination rather than pollution. Groundwater pollution can occur from on-site sanitation systems, landfill leachate, treatment

plants,

leaking

sewers,

effluent

from wastewater

petrol filling

stations, hydraulic

fracturing (fracking) or from over application of fertilizers in agriculture. Pollution (or contamination) can also occur from naturally occurring contaminants, such as arsenic or fluoride Using polluted groundwater causes hazards to public health through poisoning or the spread of disease (waterborne diseases).

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Pollution from point sources Point source water pollution refers to contaminants that enter a waterway from a single, identifiable source, such as a pipe or ditch. Examples of sources in this category include discharges from a sewage treatment plant, a factory, or a city storm drain.

Sewage Sewage typically consists of 99.9% water and 0.1% solids.Sewage contributes many classes of nutrients that lead to eutrophication. It is a major source of phosphate for example.Sewage is often contaminated with diverse compounds found in personal hygiene, cosmetics, pharmaceutical drugs , and their metabolites.Water pollution due to environmental persistent pharmaceutical pollutants can have wide-ranging consequences. When sewers overflow during storm events this can lead to water pollution from untreated sewage. Such

events

are called sanitary

sewer overflows or combined

overflows.

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sewer

Industrial wastewater Industrial wastewater could add the following pollutants to receiving water bodies if the wastewater is not treated and managed properly:  Heavy metals, including mercury, lead, and chromium  Organic matter and nutrients such as food waste: Certain industries (e.g. food processing, slaughterhouse waste, paper fibers, plant material, etc.) discharge high concentrations of BOD, ammonia nitrogen and oil and grease.  Inorganic particles such as sand, grit, metal particles, rubber residues from tires, ceramics, etc.  Toxins such as pesticides, poisons, herbicides, etc.  Pharmaceuticals,

endocrine

disrupting

compounds,

hormones,

perfluorinated compounds, siloxanes, drugs of abuse and other hazardous substances  Microplastics such as polyethylene and polypropylene beads, polyester and polyamide  Thermal pollution from power stations and industrial manufacturers 37

 Radionuclides from uranium

mining,

processing nuclear

fuel,

operating nuclear reactors, or disposal of radioactive waste.  Some industrial discharges include persistent organic pollutants such as per- and polyfluoroalkyl substances (PFAS).

Pollution from non point sources Nonpoint source (NPS) pollution refers to diffuse contamination (or pollution) of water or air that does not originate from a single discrete source. This type of pollution is often the cumulative effect of small amounts of contaminants gathered from a large area. It is in contrast to point source pollution which results from a single source. Nonpoint source pollution generally results from land runoff, precipitation, atmospheric deposition, drainage, seepage, or hydrological modification (rainfall and snowmelt) where tracing pollution back to a single source is difficult. Nonpoint source water pollution affects a water body from sources such as polluted runoff from agricultural areas draining into a river, or wind-borne debris blowing out to sea. Nonpoint

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source air pollution affects air quality, from sources such as smokestacks or car tailpipes. Although these pollutants have originated from a point source, the long-range transport ability and multiple sources of the pollutant make it a nonpoint source of pollution; if the discharges were to occur to a body of water or into the atmosphere at a single location, the pollution would be single-point.

Agriculture Agriculture is a major contributor to water pollution from nonpoint sources. The use of fertilizers as well as surface runoff from farm fields, pastures and feedlots leads

to

nutrient

pollution.In

addition

to

plant-focused

agriculture, fish-farming is also a source of pollution. Additionally, agricultural runoff often contains high levels of pesticides.

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Impacts Oxygen depletion, resulting from nitrogen pollution and eutrophication, is a common cause of fish kills.

Ecosystems Water pollution is a major global environmental problem because it can result in the degradation of all aquatic ecosystems – fresh, coastal, and ocean waters. The specific contaminants leading to pollution in water include a wide spectrum of chemicals, pathogens, and physical changes such as elevated temperature. While many of the chemicals and substances that are regulated may be naturally occurring (calcium, sodium, iron, manganese, etc.) the concentration usually determines what is a natural component of water and what is a contaminant. High concentrations of naturally occurring substances can have negative impacts on aquatic flora and fauna. Oxygen-depleting substances may be natural materials such as plant matter (e.g. leaves and grass) as well as man-made chemicals. Other natural and anthropogenic

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substances may cause turbidity (cloudiness) which blocks light and disrupts plant growth, and clogs the gills of some fish species.

Public health and waterborne diseases A study published in 2017 stated that "polluted water spread gastrointestinal diseases and parasitic infections and killed 1.8 million people" (these are also referred to as waterborne diseases). Persistent exposure to pollutants through water are environmental health hazards, which can increase the likelihood for one to develop cancer or other diseases.

Ocean acidification Ocean acidification is another impact of water pollution. Ocean acidification is the ongoing decrease in the pH value of the Earth's oceans, caused by the uptake of carbon dioxide (CO2) from the atmosphere.

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Eutrophication from nitrogen pollution Nitrogen

pollution can

cause

eutrophication,

especially

in

lakes.

Eutrophication is an increase in the concentration of chemical nutrients in an ecosystem to an extent that increases the primary productivity of the ecosystem. Subsequent negative environmental effects such as anoxia (oxygen depletion) and severe reductions in water quality may occur.   This can harm fish and other animal populations.

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Control and reduction  Pollution control philosophy One aspect of environmental protection are mandatory regulations but they are only part of the solution. Other important tools in pollution control include environmental education, economic instruments, market forces and stricter enforcements. Standards can be "precise" (for a defined quantifiable minimum or maximum value for a pollutant), or "imprecise" which would require the use of Best available technology (BAT) or Best practicable environmental option (BPEO). Market-based economic instruments for pollution control can include: charges, subsidies, deposit or refund schemes, the creation of a market in pollution credits, and enforcement incentives. Moving towards a holistic approach in chemical pollution control combines the following approaches: Integrated control measures, trans-boundary considerations, complementary and supplementary control measures, lifecycle considerations, the impacts of chemical mixtures.

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Control of water pollution requires appropriate infrastructure and management plans. The infrastructure may include wastewater treatment plants, for example sewage

treatment

plants

and industrial wastewater treatment

plants. Agricultural wastewater treatment for farms, and erosion control at construction sites can also help prevent water pollution. Effective control of urban runoff includes reducing speed and quantity of flow. Water pollution requires ongoing evaluation and revision of water resource policy at all levels (international down to individual aquifers and wells).  Industrial wastewater treatment Industrial wastewater treatment describes the processes used for treating wastewater that is produced by industries as an undesirable by-product. After treatment, the treated industrial wastewater (or effluent) may be reused or released to a sanitary sewer or to a surface water in the environment. Some industrial facilities generate wastewater that can be treated in sewage treatment plants. Most industrial processes, such as petroleum refineries, chemical and petrochemical plants have their own specialized facilities to treat their wastewaters so that the pollutant concentrations in the treated wastewater 44

comply

with

regarding

the

regulations

disposal

of

wastewaters into sewers or into rivers,

lakes

or oceans.

This

applies to industries that generate wastewater

with

high

concentrations of organic matter

Industrial wastewater treatment plant

(e.g. oil and grease), toxic pollutants (e.g. heavy metals, volatile organic compounds) or nutrients such as ammonia.   Some industries install a pretreatment system to remove some pollutants (e.g., toxic compounds), and then discharge the partially treated wastewater to the municipal sewer system.  Agricultural wastewater treatment Agricultural

wastewater

treatment is

a farm

management agenda

for

controlling pollution from confined animal operations and from surface runoff that may be contaminated by chemicals in fertilizer, pesticides, animal slurry, crop residues or irrigation water. Agricultural wastewater treatment is required for continuous confined animal operations like milk and egg 45

production. It may be performed in plants using mechanized treatment units similar to those used for industrial wastewater. Where land is available for ponds, settling basins and facultative lagoons may have lower operational costs

for

seasonal

use

conditions

from

breeding

or

harvest

cycles. Animal slurries are usually treated by containment in anaerobic lagoons before

disposal

by

spray

or

trickle

application

to

grassland. Constructed wetlands are sometimes used to facilitate treatment of animal wastes.  Management of erosion and sediment control

Silt fence installed on a construction site

Sediment from construction sites can be managed by installation of erosion controls, such as mulching and hydro seeding, and sediment controls, such as sediment basins and silt fences. Discharge of toxic chemicals such as motor

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fuels and concrete washout can be prevented by use of spill prevention and control plans, and specially designed containers (e.g. for concrete washout) and structures such as overflow controls and diversion berms. Erosion caused by deforestation and changes in hydrology (soil loss due to water runoff) also results in loss of sediment and, potentially, water pollution.  Control of urban runoff (storm water)

Urban runoff flowing into a storm drain

Effective control of urban runoff involves reducing the velocity and flow of stormwater, as well as reducing pollutant discharges. Local governments use a variety of stormwater management techniques to reduce the effects of urban runoff. These techniques, called best management practices for water

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pollution (BMPs) in some countries, may focus on water quantity control, while others focus on improving water quality, and some perform both functions. Runoff

mitigation

systems

include infiltration

basins, bio

retention systems, constructed wetlands, retention basins, and similar devices.

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Let’s Asses

1. When water is heated after reaching a particular temperature water converts from liquid to gaseous state.When we cooling the water by decreasing the temperature water converts from liquid to solid state. (a).What is meant by boiling point and melting point? (b).What are the boiling and freezing points of water ? (c).Why is there no change in temperature, When water is heated at its boiling point or melting point ? 2. Surface tension may be defined as(a).The work done per unit area in increasing the surface area of a liquid under isothermal conditions. (b).The work done per unit area in increasing the surface area of a liquid under adiabatic conditions. 49

(c).The work done per unit area in increasing the surface area of a liquid under both isothermal and adiabatic conditions. (d).Free surface energy per unit volume. 3. Water’s surface tension can be reduced by(a).Dissolving common salt in water. (b).Lowering water temperature. (c).Adding detergents to water. (d) .All of the above 4. Which are the advantage of water’s heat capacity ? 5.Why is water called the 'universal solvent'? 6. What is the major diffence between - hard water , ,soft water ? 7. Some substances when dissolved in water cause hardness of water. a) Which of the following substances cause hardness of water? Sodium chloride, Calcium bicarbonate, Calcium carbonate, Calcium sulphate, Magnesium sulphate, Calcium chloride, Magnesium carbonate

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b) The hardness due to which of the above salts cannot be removed by boiling? 8. Providing excess food for fish in an aquarium is a threat to its survival. Justify.

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Notes

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Notes

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