Here’s your concise guide to Class 9 Science Chapter 14: Natural Resources! Perfect for Class 9 students, parents, and teachers preparing for the 2025 CBSE exams, this post covers in-text questions and answers, exercise solutions, and detailed notes on Earth’s resources. Let’s dive into the Class 9 Science Chapter 14 questions, answers, and notes!
Class 9 Science Chapter 14 Notes
1. Natural Resources
- Definition: Materials provided by Earth for survival (e.g., air, water, soil).
- Types: Renewable (e.g., sunlight), Non-renewable (e.g., coal).
2. Air
- Composition: Nitrogen (78%), Oxygen (21%), others (1%).
- Role: Respiration, combustion, weather regulation.
3. Water
- Distribution: 71% of Earth; 97% saline, 3% fresh (mostly ice).
- Cycle: Evaporation, condensation, precipitation.
4. Soil
- Formation: Weathering of rocks, organic matter addition.
- Types: Sandy, clayey, loamy.
5. Biogeochemical Cycles
- Carbon Cycle: CO₂ exchange via respiration, photosynthesis.
- Nitrogen Cycle: N₂ fixation, assimilation, decomposition.
- Water Cycle: Circulation through evaporation, rainfall.
6. Pollution
- Air: CO₂, SO₂ from burning fuels.
- Water: Sewage, chemicals.
- Soil: Pesticides, waste.
These notes outline the chapter—use them for the Q&As!
In-Text Questions and Answers: Page 201
Question 1: Explain comprehensively why Earth is uniquely suited to support life, including the specific natural resources and conditions that enable this, with examples.
Answer:
Earth is uniquely suited to support life due to its balanced natural resources and conditions, creating a habitable environment unlike other planets. Key resources include air, water, and soil, paired with a moderate climate. Air, rich in oxygen (21%), sustains respiration for animals and humans—plants use CO₂ for photosynthesis, releasing O₂, as seen in forests maintaining breathable air. Water, covering 71% of Earth, is vital for all life—freshwater in rivers (e.g., Ganges) hydrates organisms, while oceans regulate temperature. Soil, formed by rock weathering and organic decay, supports plant growth—loamy soil in Punjab grows wheat, feeding millions.
Earth’s distance from the Sun (149.6 million km) ensures a temperature range (-50°C to 50°C) suitable for liquid water, unlike Mars’ cold (-140°C) or Venus’ heat (460°C). The atmosphere shields against UV rays, and gravity retains air and water—Moon lacks both, so no life thrives. Examples: coral reefs flourish in oceans, humans farm fertile plains. This synergy of resources and conditions—absent on barren planets—makes Earth a cradle for diverse life forms.
Question 2: Discuss in detail how the movement of air influences weather patterns, including the mechanisms involved and examples of resulting phenomena.
Answer:
The movement of air, driven by uneven heating of Earth’s surface, influences weather patterns through convection, pressure differences, and wind systems. Solar energy heats the equator more than the poles, warming air there—it expands, rises (low pressure), and cooler, denser air from poles sinks (high pressure), creating circulation. Winds form as air flows from high to low pressure, redistributing heat and moisture. For instance, sea breezes occur daily—land heats faster, air rises, and cooler ocean air rushes in, cooling coastal areas like Mumbai.
Monsoons in India result from summer heating of land—low pressure pulls moist ocean air, causing heavy rain (e.g., Kerala’s June floods). Jet streams, fast high-altitude winds, steer storms—winter cyclones in North India follow these paths. Mechanisms include the Coriolis effect (Earth’s rotation deflecting winds) and humidity—moist air rising condenses into clouds, as in thunderstorms. These patterns shape climate—dry deserts from sinking dry air, wet tropics from rising moist air—showing air’s dynamic role in weather diversity.
Question 3: Analyze extensively how human activities contribute to air pollution, including specific pollutants, their sources, and their effects on health and the environment.
Answer:
Human activities contribute to air pollution by releasing harmful substances, altering air quality with health and environmental impacts. Major pollutants include carbon dioxide (CO₂) and sulfur dioxide (SO₂) from burning fossil fuels—coal plants in Delhi emit SO₂, while cars release CO₂. Nitrogen oxides (NOx) from vehicle exhausts and particulate matter (PM) from construction dust add to the mix. Sources are industrial—factories burn oil, releasing smoke (e.g., Mumbai’s refineries)—and domestic, like wood stoves emitting PM in rural homes. Deforestation reduces CO₂-absorbing trees, worsening greenhouse effects.
Effects on health: SO₂ irritates lungs, causing asthma—Delhi’s smog hospitalizes thousands yearly. PM enters bloodstreams, linked to heart disease. Environmentally, CO₂ traps heat, raising global temperatures (e.g., melting Arctic ice), while NOx and SO₂ form acid rain, killing fish in lakes (e.g., Scandinavian waters). These pollutants, from power generation to transport, degrade air, threatening ecosystems and human life, necessitating cleaner alternatives.
In-Text Questions and Answers: Page 206
Question 1: Provide a thorough explanation of how the water cycle maintains water availability on Earth, including each stage and its significance.
Answer:
The water cycle maintains water availability on Earth by continuously circulating water through evaporation, condensation, and precipitation, ensuring a renewable supply. It begins with evaporation—sun heats oceans, rivers (e.g., Amazon), turning liquid water into vapor, rising into the atmosphere. This stage lifts water from 97% saline sources, making it accessible. Condensation follows—vapor cools at higher altitudes, forming clouds (e.g., monsoon clouds over India), concentrating water as droplets.
Precipitation—rain, snow, or hail—returns water to land and seas, replenishing rivers, lakes (e.g., Himalayan snowmelt feeding Ganges), and groundwater. Runoff and infiltration redistribute it—rain soaks into soil, refilling aquifers. Significance: evaporation purifies water, condensation gathers it, and precipitation delivers it, sustaining crops (e.g., rice paddies), drinking water, and ecosystems (e.g., wetlands). Without this cycle, freshwater (3% of total) would deplete, halting life—its balance keeps Earth hydrated and habitable.
Question 2: Elaborate in detail on how soil is formed and why it is critical for agriculture, including the processes involved and its role in food production.
Answer:
Soil forms through weathering of rocks and organic matter accumulation, a slow process critical for agriculture as it supports plant growth for food production. Physical weathering breaks rocks—wind, water, or temperature changes (e.g., frost cracking Himalayan stones) fragment them into sand or clay. Chemical weathering alters composition—rainwater with CO₂ forms carbonic acid, dissolving limestone into minerals. Biological activity adds organic matter—dead plants, animals decompose via microbes, enriching soil with humus (e.g., forest leaf litter).
Over centuries, layers form—topsoil holds nutrients, subsoil supports roots. Soil’s critical for agriculture: it anchors plants (e.g., wheat in Punjab), supplies nutrients (nitrogen, phosphorus from humus), and retains water—loamy soil balances drainage and moisture for rice. Example: fertile Gangetic plains yield 50% of India’s crops due to alluvial soil. Without soil, plants can’t grow at scale—its texture, fertility, and water-holding capacity make it the backbone of global food security.
Exercise Questions and Answers: Page 215
Question 1: A region receives heavy rainfall but faces water scarcity. Analyze in detail why this occurs, including possible reasons and solutions.
Answer:
Heavy rainfall yet water scarcity in a region occurs due to poor management and environmental factors. Reasons: Runoff—steep slopes or deforestation (e.g., Western Ghats) let rain flow away instead of soaking in, as trees slow water. No storage—lack of dams or tanks (e.g., rural India) fails to capture rain, unlike reservoirs in Tamil Nadu. Pollution—industrial waste (e.g., rivers near factories) makes water unusable.
Overuse—irrigation or population growth (e.g., cities like Chennai) depletes groundwater faster than recharge. Solutions: Build check dams to store runoff, plant trees to enhance infiltration, treat sewage to reuse water, and promote rainwater harvesting—rooftop tanks in Bangalore store millions of liters. These address loss, storage, and quality, turning abundance into availability.
Question 2: State two ways humans affect the nitrogen cycle and explain thoroughly how each disrupts it, with examples.
Answer:
Two ways humans affect the nitrogen cycle:
- Fertilizer Use: Adding synthetic nitrogen (e.g., urea in Punjab farms) boosts crop growth but disrupts natural fixation. Excess leaches into rivers, causing algal blooms (e.g., Yamuna’s green patches), depleting oxygen and killing fish.
- Burning Fossil Fuels: Cars, factories (e.g., Delhi’s traffic) release NOx, increasing atmospheric nitrogen. This forms acid rain (e.g., Northeast India), acidifying soils and hindering plant uptake, unbalancing ecosystems. Both overload the cycle, shifting nitrogen from soil to water or air, harming biodiversity.
Class 9 Science Chapter 14: Natural Resources unpacks Earth’s essentials for your 2025 CBSE exams. With these notes and Q&As, you’re set to shine. Explore NCERT solutions for more, and comment your doubts—we’re here!
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