2. Give short answer.
(i) List the impurities present in rain water.
Answer: Rainwater is not pure H₂O; it contains various impurities picked up from the atmosphere:
Dissolved Gases: Carbon dioxide (CO₂), sulfur dioxide (SO₂), nitrogen oxides (NOx), and oxygen (O₂). Particulate Matter: Dust, pollen, smoke, and soot. Microorganisms: Bacteria and fungal spores. Dissolved Salts: Trace amounts of sea salts (if rain falls near coastal areas). Due to dissolved CO₂, natural rainwater is slightly acidic (pH ~5.6).
(ii) List toxic substances present in household wastes.
Answer: Household wastes contain several toxic substances:
Cleaning Agents: Bleach, ammonia, and detergents. Batteries: Contain heavy metals like mercury, cadmium, and lead. Paints and Solvents: Contain volatile organic compounds (VOCs) and heavy metals. Pharmaceuticals: Unused medicines can contaminate water. Pesticides and Herbicides: Used in gardens. Electronic Waste: Contains lead, mercury, and cadmium.
(iii) In what ways, industrial wastes pollute water.
Answer: Industrial wastes pollute water in several ways:
Discharge of Toxic Chemicals: Heavy metals (lead, mercury, cadmium), acids, and organic solvents. Thermal Pollution: Discharging hot water from cooling processes raises water temperature, reducing dissolved oxygen. Nutrient Pollution: Release of nitrates and phosphates causing eutrophication. Suspended Solids: Release of particulate matter that blocks sunlight and smothers aquatic life. Oil Spills: From refineries and transport.
(iv) What is water pollution?
Answer: Water pollution is the contamination of water bodies (lakes, rivers, oceans, aquifers, and groundwater) with harmful substances, making it unsafe for human use and harmful to aquatic ecosystems. It occurs when pollutants are discharged directly or indirectly into water without adequate treatment. Pollutants include industrial effluents, agricultural runoff, sewage, and plastic waste.
(v) List some waterborne diseases.
Answer: Waterborne diseases are caused by pathogenic microorganisms transmitted through contaminated water. Examples include:
Cholera Typhoid Hepatitis A Dysentery Diarrhea Giardiasis Cryptosporidiosis
(vi) What are pathogenic microorganisms?
Answer: Pathogenic microorganisms are bacteria, viruses, protozoa, or fungi that cause disease in their host. In water, they are often introduced through fecal contamination from sewage or animal waste. Examples include Vibrio cholerae (cholera), Salmonella typhi (typhoid), and Giardia lamblia (giardiasis). They can cause severe gastrointestinal illnesses.
3. How does tap water differ from distilled water?
Answer: Tap water is treated water supplied through pipes for domestic use. It contains dissolved minerals (calcium, magnesium, sodium), traces of chlorine (used for disinfection), and possibly other impurities. Distilled water is purified by boiling and condensation, removing almost all impurities, minerals, and salts. Distilled water is neutral (pH 7) and has a flat taste, while tap water has a variable pH and taste due to dissolved minerals.
4. Why are municipal water supplies treated with aluminium sulphate?
Answer: Municipal water supplies are treated with aluminium sulphate (alum) during the coagulation and flocculation process. Alum is added to water to neutralize the negative charges on suspended particles (clay, silt, organic matter). This allows the particles to clump together into larger masses called "flocs." These flocs can then be easily removed by sedimentation and filtration, clarifying the water.
5. What are some health effects of biological contamination of water?
Answer: Biological contamination of water (by bacteria, viruses, protozoa) causes various health effects:
Gastrointestinal Illnesses: Diarrhea, vomiting, and abdominal cramps.
Life-threatening Diseases: Cholera, typhoid, hepatitis A. Parasitic Infections: Giardiasis, cryptosporidiosis. Long-term Effects: Malnutrition and developmental delays in children due to repeated infections. Outbreaks: Epidemics of waterborne diseases in communities.
6. Identify the negative effects of water pollutants on life.
Answer: Water pollutants have severe negative effects on life:
Human Health: Waterborne diseases, poisoning by heavy metals (lead, mercury), and cancer from carcinogenic pollutants. Aquatic Life: Eutrophication depletes oxygen, killing fish. Heavy metals accumulate in fish tissues, affecting predators and humans. Plastic pollution kills marine animals through ingestion and entanglement. Ecosystems: Destruction of coral reefs, disruption of food webs, and loss of biodiversity. Economy: Increased water treatment costs, loss of fisheries, and reduced tourism.
7. Water scarcity is an important issue in Pakistan. Give your comments on it.
Answer: Water scarcity is a critical issue in Pakistan due to several factors:
Rapid Population Growth: Increasing demand for water. Climate Change: Reduced rainfall and melting glaciers. Inefficient Irrigation: Flood irrigation wastes huge amounts of water. Water Pollution: Contamination reduces usable water. Lack of Storage: Insufficient dams to store water. Groundwater Depletion: Over-extraction of groundwater. This scarcity threatens agriculture, industry, and domestic supply, requiring urgent conservation and management
strategies.
8. What are fertilizers?
Answer: Fertilizers are chemical substances added to soil to supply essential nutrients (nitrogen, phosphorus, potassium) for plant growth. They can be natural (manure, compost) or synthetic (urea, ammonium nitrate, superphosphate). While they increase crop yields, excessive use can cause water pollution through runoff, leading to eutrophication.
