WATER 8.1.1 Chemical tests to check purity of water Litmus test: Pure water is neutral → no change in red/blue litmusAnhydrous Copper Sulfate: White → turns blue if water presentCobalt Chloride paper: Blue → turns pink if water present8.1.2 Potable water Water that is safe to drink. It should be free from harmful bacteria, chemicals and suspended impurities. 8.1.3 Treatment of water Filtration: Remove solid impurities using sand/charcoal filtersChlorination: Add chlorine to kill bacteria and germs8.1.4 Uses of water Domestic: Drinking, cooking, washing, bathingIndustrial: Cooling, solvent, in chemical reactions, power generation 8.1.5 Sources of water Surface water: Rivers, lakes, seasGround water: Wells, tube wells, springsRain water 8.1.6 Problems of inadequate supply Drought, poor sanitation, spread of diseases, crop failure, industrial problems AIR 8.1.7 Changes in air composition - Early Earth to Present Early: CO2, CH4, NH3, H2O vapor. No O2 - Reducing atmospherePresent: N2 78%, O2 21% - Oxidizing atmosphereReason: Photosynthesis increased O2, CO2 dissolved in oceans 8.1.8 Relative composition of gasesGas% by VolumeNitrogen N278%Oxygen O221%Argon + others0.93%CO20.04%8.1.9 Separation of N2 and O2 by Fractional Distillation Liquid air is warmed slowly. N2 boils at -196°C first, O2 at -183°C later. Based on different boiling points. 8.1.10 Uses of N2 and O2 Nitrogen: Fertilizers, inert atmosphere in food packing, liquid N2 as coolantOxygen: Respiration, combustion, welding, hospitals 8.1.11 Sources of Air Pollutants CO: Incomplete combustion of fuelsLead compounds: From petrolNOx: Vehicle exhausts, lightningCO2: Burning of fossil fuels, respirationCH4: Paddy fields, cattle, landfillsSO2: Burning of coal and oil, industries8.1.12 Negative effects Global warming: CO2, CH4 trap heatAcid rain: SO2, NOx → H2SO4, HNO3Respiratory problems: Dust, SO2, NOxGround level ozone: SmogBrain damage: Lead compoundsReduced O2 carrying capacity: CO binds with hemoglobinDamage to environment: Crop damage, building corrosion8.1.13 Strategies to reduce air pollution Scrubbers, Catalytic converters, Flue gas desulphurisation, Government laws, Change behavior, Use renewable energy 8.1.14 Carbon Cycle Stages CO2 in air → Photosynthesis by plants → Animals eat plants → Respiration releases CO2 → Fossil fuels → Burning releases CO2 RUSTING 8.1.15 Conditions for rusting Iron + O2 + Water + Electrolyte are needed. 4Fe+3O2+6H2O→4Fe(OH)3 8.1.16 Methods of rust prevention Coating: Paint, grease, oilGalvanising: Coating with zinc8.1.17 Sacrificial protection A more reactive metal like Zn or Mg is attached to iron. It rusts instead of iron. Used in ships and pipelines.
WATER
8.1.1 Chemical tests to check purity of water
Litmus test: Pure water is neutral → no change in red/blue litmusAnhydrous Copper Sulfate: White → turns blue if water presentCobalt Chloride paper: Blue → turns pink if water present8.1.2 Potable water
Water that is safe to drink. It should be free from harmful bacteria, chemicals and suspended impurities.
8.1.3 Treatment of water
Filtration: Remove solid impurities using sand/charcoal filtersChlorination: Add chlorine to kill bacteria and germs8.1.4 Uses of water
Domestic: Drinking, cooking, washing, bathingIndustrial: Cooling, solvent, in chemical reactions, power generation
8.1.5 Sources of water
Surface water: Rivers, lakes, seasGround water: Wells, tube wells, springsRain water
8.1.6 Problems of inadequate supply
Drought, poor sanitation, spread of diseases, crop failure, industrial problems
AIR
8.1.7 Changes in air composition - Early Earth to Present
Early: CO2, CH4, NH3, H2O vapor. No O2 - Reducing atmospherePresent: N2 78%, O2 21% - Oxidizing atmosphereReason: Photosynthesis increased O2, CO2 dissolved in oceans
8.1.8 Relative composition of gasesGas% by VolumeNitrogen N278%Oxygen O221%Argon + others0.93%CO20.04%8.1.9 Separation of N2 and O2 by Fractional Distillation
Liquid air is warmed slowly. N2 boils at -196°C first, O2 at -183°C later. Based on different boiling points.
8.1.10 Uses of N2 and O2
Nitrogen: Fertilizers, inert atmosphere in food packing, liquid N2 as coolantOxygen: Respiration, combustion, welding, hospitals
8.1.11 Sources of Air Pollutants
CO: Incomplete combustion of fuelsLead compounds: From petrolNOx: Vehicle exhausts, lightningCO2: Burning of fossil fuels, respirationCH4: Paddy fields, cattle, landfillsSO2: Burning of coal and oil, industries8.1.12 Negative effects
Global warming: CO2, CH4 trap heatAcid rain: SO2, NOx → H2SO4, HNO3Respiratory problems: Dust, SO2, NOxGround level ozone: SmogBrain damage: Lead compoundsReduced O2 carrying capacity: CO binds with hemoglobinDamage to environment: Crop damage, building corrosion8.1.13 Strategies to reduce air pollution
Scrubbers, Catalytic converters, Flue gas desulphurisation, Government laws, Change behavior, Use renewable energy
8.1.14 Carbon Cycle Stages
CO2 in air → Photosynthesis by plants → Animals eat plants → Respiration releases CO2 → Fossil fuels → Burning releases CO2
RUSTING
8.1.15 Conditions for rusting
Iron + O2 + Water + Electrolyte are needed. 4Fe+3O2+6H2O→4Fe(OH)3
8.1.16 Methods of rust prevention
Coating: Paint, grease, oilGalvanising: Coating with zinc8.1.17 Sacrificial protection
A more reactive metal like Zn or Mg is attached to iron. It rusts instead of iron. Used in ships and pipelines.
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This guide explores the significance of water chemistry, emphasizing the need for assessment, treatment, and conservation to ensure safe water. It covers methods for testing water purity, including litmus tests and reactions with copper sulfate and cobalt paper. Additionally, it defines potable water, highlighting its safety for human consumption by excluding harmful microbes and chemicals while removing suspended impurities.