Chemistry of the environment-water
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Title: Quick AQUA Water
Authors: Yifan, Riley, Kaixin, Josiah, Nsofwa
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10 Chemistry of the Environment
10.1 Water
Core Objectives:
Describe chemical tests for water presence using anhydrous cobalt(II) chloride and anhydrous copper(II) sulfate.
Describe how to test the purity of water using melting point and boiling point.
Explain why distilled water is preferred in practical chemistry.
Identify substances found in natural water sources:
(a) Dissolved oxygen
(b) Metal compounds
(c) Plastics
(d) Sewage
(e) Harmful microbes
(f) Nitrates from fertilizers
(g) Phosphates from fertilizers and detergents
State beneficial substances:
(a) Dissolved oxygen for aquatic life
(b) Essential minerals from metal compounds
Identify harmful substances:
(a) Toxic metal compounds
(b) Plastics harming aquatic life
(c) Sewage containing harmful microbes
(d) Nitrates and phosphates causing deoxygenation and damage to aquatic life
Describe domestic water treatment:
(a) Sedimentation and filtration to remove solids
(b) Use of carbon to remove tastes and odours
(c) Chlorination to kill microbes
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Objectives 1-3
Chemical tests for water using anhydrous cobalt(II) chloride and anhydrous copper(II) sulfate.
Purity test for water using melting point and boiling point.
Explanation of distilled water preference in chemistry.
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Testing for Water with Anhydrous Cobalt Chloride
Appearance: Blue in anhydrous form; turns pink when hydrated.
Reaction:
Test: Add suspected substance to CoCl2; observe color change. Pink indicates water presence.
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Testing for Water with Anhydrous Copper(II) Sulfate
Appearance: White and powdery; turns blue when hydrated.
Reaction:
Test: Add anhydrous copper(II) sulfate to substance; if it turns blue, water is present.
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Testing the Purity of Water: Melting Point
Pure water freezes at 0 degrees C; impurities lower this temperature.
Test: Cool water and note freezing temperature. Below 0 degrees indicates impurity.
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Testing the Purity of Water: Boiling Point
Pure water boils at 100 degrees C; impurities raise this temperature.
Test: Heat water; if boiling point exceeds 100 degrees, it is impure.
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Why Use Distilled Water
Distilled water is preferred in chemistry due to its purity.
Free from minerals and salts that could influence reactions and results.
Ensures consistent quality and neutral pH.
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Substances in Natural Water Sources
Water may contain various substances:
(a) Dissolved oxygen
(b) Metal compounds
(c) Plastics
(d) Sewage
(e) Harmful microbes
(f) Nitrates from fertilizers
(g) Phosphates from fertilizers and detergents
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Sources of Natural Water
Natural sources include lakes, rivers, and aquifers.
Aquifer: A rock formation that stores water.
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Dissolved Oxygen
Refers to the concentration of oxygen gas in water.
Oxygen is directly absorbed from the atmosphere.
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Metal Compounds
Common metals include lead, nickel, arsenic from:
Household plumbing
Cement plants
Natural mineral deposits
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Plastics
Contaminated through rainwater or wind runoff.
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Sewage
Sources of contamination:
Bursting or flooding of sewage pipes
The practice of illegal dumping
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Harmful Microbes
Contaminants from sewage and factory waste, can also come from fertilizers.
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Nitrates from Fertilizers
Highly soluble and can contaminate groundwater during rain.
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Phosphates from Fertilizers and Detergents
Less soluble than nitrates but can leach into groundwater.
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Beneficial Substances in Water
Beneficial impurities include:
(a) Dissolved oxygen for aquatic life.
(b) Essential minerals from metal compounds.
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Importance of Beneficial Impurities
Dissolved Oxygen: Essential for respiration in aquatic animals.
Essential Minerals: Include iron, sodium, zinc, copper, magnesium, calcium; vital for various biological processes.
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Potentially Harmful Substances
Harmful substances:
(a) Toxic metal compounds
(b) Plastics harming aquatic life
(c) Sewage with harmful microbes
(d) Nitrates and phosphates leading to deoxygenation
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Summary of Natural Water Impurities
Common impurities:
Dissolved oxygen
Metal compounds
Plastics
Sewage
Harmful microbes
Nitrates and phosphates
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Toxic Materials in Water
Toxic metals (e.g., mercury, lead) and microplastics harm wildlife.
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Sewage Contamination
Sewage causes diseases like cholera and typhoid when it contaminates natural water.
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Effects of Nitrates and Phosphates
Increase in nitrates/phosphates leads to algal blooms blocking sunlight for aquatic plants.
Results in increased bacteria and decreased oxygen availability for aquatic life.
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Objectives for Water Treatment
Treatment methods include:
(a) Sedimentation and filtration
(b) Carbon filtration for taste and odour
(c) Chlorination for microbe elimination
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Sedimentation & Filtration
Sedimentation Process:
Water stored to allow particles to settle.
Alum added to help agglomerate smaller particles.
Filtration Process:
Water passes through layers of materials to remove impurities: fine sand, gravel, activated carbon.
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Use of Carbon in Filtration
Activated carbon filters improve taste and odor by adsorption of contaminants.
Removes unwanted chemicals, including pesticides and chlorine by-products.
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Chlorination Process
Chlorine compounds added to water kill harmful microorganisms.
Provides ongoing protection against contaminants in water supply.