Earth As a System Energy Matter and Life — Class 9 Science NCERT Solutions (Free)
Free step-by-step NCERT solutions for Class 9 Science chapter "Earth As a System Energy Matter and Life" — 9 important questions with detailed answers for CBSE board exam preparation.
TL;DR: Free step-by-step NCERT solutions for Class 9 Science chapter "Earth As a System Energy Matter and Life" — 9 important questions with detailed answers…
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Key Questions Covered:
- What are natural resources? Classify and explain air, water, and soil.
- Explain the water cycle (hydrological cycle) and its stages.
- Explain the nitrogen cycle and its importance.
- Explain the carbon cycle and its stages.
- Explain the oxygen cycle and its significance.
- What is the greenhouse effect? How do greenhouse gases cause global warming?
- + 3 more questions in the full chapter
Solutions Summary:
| Question | Status |
|---|---|
| What are natural resources? Classify and explain air, wat… | ✓ Solved |
| Explain the water cycle (hydrological cycle) and its stages. | ✓ Solved |
| Explain the nitrogen cycle and its importance. | ✓ Solved |
| Explain the carbon cycle and its stages. | ✓ Solved |
| Explain the oxygen cycle and its significance. | ✓ Solved |
| What is the greenhouse effect? How do greenhouse gases ca… | ✓ Solved |
Showing 6 of 9 questions
Q1: What are natural resources? Classify and explain air, water, and soil.
Natural resources = Materials/energy from nature used by organisms.
Classification: Renewable (replenished naturally) and Non-renewable (finite supply).
AIR: Mixture of gases (N₂ 78%, O₂ 21%, Ar 0.9%, CO₂ 0.04%, other gases)
• Renewable resource
• Provides oxygen for respiration
• Used in combustion, photosynthesis
WATER: Essential liquid covering 71% of Earth
• Renewable (through water cycle)
• Solvent, participant in biochemical reactions
• Habitats for aquatic organisms
SOIL: Weathered rock +...
Q2: Explain the water cycle (hydrological cycle) and its stages.
Water cycle = Continuous movement of water between atmosphere, hydrosphere, and lithosphere.
Stages:
(1) Evaporation: Water from surface (ocean, lake, river, soil) → Water vapor (due to solar heat)
(2) Transpiration: Water from plants → Water vapor (through leaves)
(3) Condensation: Water vapor → Liquid water droplets (in atmosphere, forms clouds)
(4) Precipitation: Water falls as rain, snow, hail, sleet
(5) Infiltration: Water soaks into soil (groundwater)
(6) Percolation: Water moves through s...
Q3: Explain the nitrogen cycle and its importance.
Nitrogen cycle = Movement of nitrogen between atmosphere, soil, organisms, and back.
Stages:
(1) Nitrogen fixation: Atmospheric N₂ → Nitrates/Ammonia (by nitrogen-fixing bacteria)
• Bacteria in soil, root nodules of legumes
• Lightning also fixes nitrogen
(2) Nitrification: Ammonia (NH₃) → Nitrites (NO₂⁻) → Nitrates (NO₃⁻)
• By nitrifying bacteria (in soil)
(3) Assimilation: Plants absorb nitrates → Plant proteins
• Animals eat plants → Animal proteins
(4) Ammonification: Dead organisms, waste →...
Q4: Explain the carbon cycle and its stages.
Carbon cycle = Movement of carbon between atmosphere, organisms, and geosphere.
Stages:
(1) Carbon fixation: Atmospheric CO₂ + H₂O → Glucose (by photosynthesis in plants)
(2) Respiration: Organisms oxidize glucose → CO₂ + H₂O (returns to atmosphere)
(3) Consumption: Animals eat plants/other animals (carbon in food)
(4) Decomposition: Dead organisms → CO₂ (by decomposers)
(5) Fossil fuel combustion: Fossil fuels → CO₂ (coal, oil, natural gas burning)
(6) Sedimentation: Some carbon settles as sedi...
Q5: Explain the oxygen cycle and its significance.
Oxygen cycle = Movement of oxygen between atmosphere, organisms, and compounds.
Stages:
(1) Photosynthesis: Plants release O₂ (H₂O → O₂ + H⁺)
(2) Respiration: Organisms use O₂ (Glucose + O₂ → CO₂ + H₂O)
(3) Combustion: Fossil fuels burn (consume O₂, release CO₂)
(4) Decomposition: Decomposers use O₂
(5) Oxidation-reduction reactions: In soil and water
Key processes:
• Photosynthesis: Main source of atmospheric O₂
• Respiration: Major consumer of O₂
• Combustion: Increases O₂ consumption
Signific...
Q6: What is the greenhouse effect? How do greenhouse gases cause global warming?
Greenhouse effect = Phenomenon where atmospheric gases trap heat, warming Earth's surface.
Greenhouse gases: CO₂, CH₄ (methane), N₂O (nitrous oxide), water vapor, CFCs
Mechanism:
(1) Sunlight enters atmosphere and reaches Earth's surface
(2) Surface absorbs heat and radiates infrared radiation (heat)
(3) Greenhouse gases absorb infrared radiation
(4) Heat radiates back to surface and space
(5) More gases → More heat trapped → Surface temperature increases
Causes of increased greenhouse effect (G...
Showing 6 of 9 questions. Visit the full page for complete solutions.
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