Important Questions Class 9 Science Exploration Chapter 13 cover Earth as an interconnected system where energy and matter move through the geosphere, hydrosphere, cryosphere, atmosphere and biosphere. For CBSE Class 9 Science Exploration 2026-27, this chapter connects solar radiation, uneven heating, winds, ocean currents, biogeochemical cycles, climate change and human impact.
Earth works through connected spheres rather than separate land, water, air and life processes. In Earth as a System: Energy, Matter, and Life, students learn how solar radiation drives uneven heating, winds, ocean currents and the water cycle. The chapter also explains how matter moves through the carbon, nitrogen and oxygen cycles, and how human activities disturb this balance. Warmer oceans, melting glaciers, deforestation, excess fertilisers and greenhouse gases show how one change can affect many Earth spheres at once. These Important Questions Class 9 Science Exploration Chapter 13 help students revise MCQs, short answers, long answers and case-based questions for exam preparation.
Key Takeaways
- Earth system: The geosphere, hydrosphere, cryosphere, atmosphere and biosphere interact continuously.
- Solar radiation: Uneven heating of Earth drives winds, ocean currents, weather and the water cycle.
- Biogeochemical cycles: Water, carbon, nitrogen and oxygen cycles recycle matter needed for life.
- Human impact: Fossil fuels, deforestation, excess fertilisers and pollution disturb Earth’s natural processes.
Important Questions Class 9 Science Exploration Chapter 13 Exam Pattern Overview
The CBSE Class 9 Science exam includes an 80-mark annual theory paper of 3 hours and a 20-mark internal assessment. The paper checks conceptual understanding, application, reasoning and case-based learning across Physics, Chemistry, Biology and Earth Science topics. For Earth as a System: Energy, Matter, and Life, students should practise MCQs, diagram-based answers, cause-effect questions and environmental application questions.
CBSE Class 9 Science Theory Exam Pattern
| Section |
Question Type |
No. of Questions |
Marks |
| Section A |
MCQs, assertion-reasoning and 1-mark objective questions |
20 |
20 |
| Section B |
Very Short Answer questions |
6 |
12 |
| Section C |
Short Answer questions |
7 |
21 |
| Section D |
Long Answer questions |
3 |
15 |
| Section E |
Case-based / Source-based questions |
3 |
12 |
| Total |
|
|
80 |
For Important Questions for Class 9 Science Exploration Chapter 13, students should focus on Earth’s spheres, solar radiation, albedo, greenhouse effect, atmosphere layers, winds, ocean currents, water cycle, carbon cycle, nitrogen cycle, oxygen cycle, eutrophication, deforestation and climate change examples.
MCQs and Objective Questions from Class 9 Science Exploration Chapter 13
These questions test quick recall, concept clarity and application. In this chapter, objective questions usually come from definitions, Earth spheres, atmospheric layers, cycles, greenhouse gases and cause-effect links.
Q1. Which option best describes the role of biogeochemical cycles in an ecosystem?
(a) To provide food directly to all organisms
(b) To recycle essential nutrients between biotic and abiotic components
(c) To create new elements for living organisms
(d) To remove all pollutants from organisms
Answer: (b) To recycle essential nutrients between biotic and abiotic components.
Biogeochemical cycles move matter such as carbon, nitrogen, oxygen and water between living and non-living parts of Earth.
Q2. Which process is primarily responsible for warming Earth?
(a) Solar radiation is immediately absorbed by carbon dioxide and released as heat.
(b) The atmosphere’s tiny particles directly heat Earth by absorbing all sunlight.
(c) Earth’s surface absorbs solar radiation, re-radiates heat and greenhouse gases trap part of it.
(d) Earth is heated only by radiation reflected by clouds.
Answer: (c) Earth’s surface absorbs solar radiation, re-radiates heat and greenhouse gases trap part of it.
This process keeps Earth warm enough for life, but excess greenhouse gases intensify warming.
Q3. Which Earth sphere includes glaciers, snow and polar ice caps?
(a) Geosphere
(b) Hydrosphere
(c) Cryosphere
(d) Biosphere
Answer: (c) Cryosphere.
The cryosphere includes solid forms of water such as ice, snow, glaciers and polar ice caps.
Q4. Which atmospheric layer contains most weather phenomena?
(a) Troposphere
(b) Stratosphere
(c) Mesosphere
(d) Exosphere
Answer: (a) Troposphere.
Most weather phenomena such as clouds, rain, storms and winds occur in the troposphere.
Q5. Which surface has the highest albedo?
(a) Black soil
(b) Ocean water
(c) Snow
(d) Asphalt road
Answer: (c) Snow.
Snow reflects a large fraction of incoming solar radiation, so it has high albedo.
Q6. Assertion: Deforestation can affect river flow.
Reason: Tree roots hold soil and vegetation supports infiltration and transpiration.
(a) Both Assertion and Reason are true, and Reason correctly explains Assertion.
(b) Both are true, but Reason does not explain Assertion.
(c) Assertion is true, but Reason is false.
(d) Assertion is false, but Reason is true.
Answer: (a) Both Assertion and Reason are true, and Reason correctly explains Assertion.
Deforestation increases runoff and soil erosion while reducing infiltration and local moisture recycling.
Very Short Answer Questions from Earth as a System Class 9
These 2-mark style answers should define the concept and add one scientific point or example.
Q7. What are the five main spheres of Earth?
The five main spheres of Earth are geosphere, hydrosphere, cryosphere, atmosphere and biosphere.
Geosphere includes rocks and soil, hydrosphere includes liquid water, cryosphere includes ice and snow, atmosphere includes air, and biosphere includes living organisms.
Q8. What is insolation?
Insolation is the amount of solar radiation that reaches Earth’s surface.
It warms Earth’s surface and atmosphere, and helps drive winds, ocean currents and the water cycle.
Q9. What is albedo?
Albedo is the fraction of solar radiation reflected by a surface.
High albedo surfaces reflect more sunlight and remain cooler, while low albedo surfaces absorb more sunlight and become warmer.
Q10. Why is the ozone layer important?
The ozone layer absorbs harmful ultraviolet radiation from the Sun.
It protects living organisms from damage to skin, eyes and ecosystems.
Q11. Name three greenhouse gases.
Three greenhouse gases are carbon dioxide, methane and water vapour.
These gases trap outgoing infrared radiation and help maintain Earth’s temperature.
Q12. What is eutrophication?
Eutrophication is the excessive growth of algae in water bodies due to high nutrient levels, especially nitrates and phosphates.
It reduces dissolved oxygen in water and can kill fish and other aquatic organisms.
Short Answer Questions on Energy, Matter and Earth’s Spheres
These 3-mark style answers should include the cause, process and result. Most questions from this chapter check how one Earth process affects another.
Q13. How does a change in one Earth sphere affect other spheres?
Earth’s spheres are interconnected, so a disturbance in one sphere can affect the others.
For example, less snowfall affects the cryosphere. This reduces meltwater supply to lakes and rivers in the hydrosphere. Less water can reduce grass growth in the biosphere and affect animals that depend on it.
Q14. How does warming of Arabian Sea water affect the southwest monsoon in India?
Warmer Arabian Sea water causes more evaporation.
This adds more moisture to the atmosphere and can disturb monsoon patterns. Some regions may receive heavy rainfall and floods, while others may face drought. This shows the link between the hydrosphere, atmosphere and biosphere.
Q15. Why does Earth’s surface heat unevenly?
Earth’s surface heats unevenly because solar radiation reaches different latitudes at different angles.
Near the equator, sunlight is concentrated over a smaller area, causing stronger heating. Near the poles, the same radiation spreads over a larger area, causing weaker heating. Land and water also heat at different rates.
Q16. How are valley and mountain breezes formed?
During the day, mountain slopes heat faster than the valley floor. Warm air over the slopes rises and cooler air from the valley moves up the slopes. This is called a valley breeze.
At night, mountain slopes cool faster. Cool and dense air flows down into the valley. This is called a mountain breeze.
Q17. How do ocean currents regulate climate?
Ocean currents transfer heat from the equator toward the poles.
Warm currents reduce temperature differences across Earth. For example, the North Atlantic Drift carries warm water toward northwestern Europe, keeping many ports ice-free in winter. Ocean currents also transport nutrients and support marine ecosystems.
Q18. How does climate change affect the water cycle?
Climate change increases evaporation and changes rainfall patterns.
A warmer atmosphere can hold more moisture, causing heavier rainfall in some regions and droughts in others. Melting glaciers add water to rivers and raise sea levels over time. Intense rainfall also increases runoff, soil erosion and reduces groundwater recharge.
Q19. Why is excess carbon dioxide in the atmosphere undesirable?
Carbon dioxide is needed by plants and helps maintain Earth’s temperature.
Excess CO₂ strengthens the greenhouse effect and causes global warming. This can melt glaciers, raise sea levels, intensify monsoons, increase extreme weather and affect agriculture.
Long Answer Questions on Earth’s Processes and Biogeochemical Cycles
These 5-mark style questions need organised answers. Use headings, steps and examples to show the links between Earth’s spheres and natural cycles.
Q20. Explain the interrelationship between different spheres of Earth with examples.
Earth’s spheres are closely connected. A change in one sphere can affect several others.
The atmosphere affects the hydrosphere through rainfall and evaporation. The hydrosphere affects the biosphere by providing water to plants, animals and humans. The cryosphere supplies water to rivers through melting snow and glaciers. The geosphere provides soil and minerals for plants. The biosphere affects the atmosphere through photosynthesis and respiration.
For example, rising atmospheric temperature melts glaciers in the cryosphere. This adds water to rivers and oceans in the hydrosphere. Sea levels may rise and coastal habitats in the biosphere may be damaged.
Deforestation also shows this interrelationship. It reduces photosynthesis, increases soil erosion, decreases transpiration, affects rainfall and destroys habitats. This proves that Earth functions as a delicate system.
Q21. Explain the carbon cycle and the effect of human activities on it.
The carbon cycle is the movement of carbon between the atmosphere, biosphere, geosphere and hydrosphere.
Plants absorb carbon dioxide from the atmosphere during photosynthesis and convert it into glucose. Animals get carbon by eating plants or other animals. Carbon returns to the atmosphere through respiration, decomposition and combustion. Some carbon is stored for long periods in oceans, shells, carbonate rocks and fossil fuels.
Human activities disturb this cycle. Burning coal, oil and gas releases stored carbon as CO₂ very quickly. Deforestation reduces the number of trees that absorb CO₂. Excess carbon dioxide intensifies the greenhouse effect, causing global warming, sea-level rise and extreme weather.
India is increasing solar and renewable energy use to reduce carbon emissions and restore balance.
Q22. Explain the nitrogen cycle.
The nitrogen cycle is the movement of nitrogen between air, soil, water and living organisms.
Atmospheric nitrogen cannot be directly used by plants. Nitrogen-fixing bacteria such as Rhizobium and Azotobacter convert nitrogen gas into ammonia. Nitrifying bacteria convert ammonia into nitrites and then nitrates. Plants absorb nitrates from soil and use them to make proteins and nucleic acids.
Animals get nitrogen by eating plants or other animals. When organisms die or produce waste, decomposers break down organic matter and return ammonia to the soil. Denitrifying bacteria convert nitrates back into nitrogen gas, completing the cycle.
Lightning and the Haber-Bosch process also fix nitrogen. Fertilisers made through this process support agriculture, but overuse can pollute water bodies and cause eutrophication.
Q23. Explain the human impact on Earth’s natural processes.
Human activities disturb natural cycles and Earth’s spheres in many ways.
Burning fossil fuels releases excess CO₂, which intensifies the greenhouse effect and causes global warming. Deforestation reduces photosynthesis, decreases transpiration, increases soil erosion and destroys habitats. Excess fertilisers add nitrates to rivers and lakes, causing algal blooms and eutrophication.
Vehicular emissions react with sunlight and form smog and harmful ground-level ozone. Pollution affects the atmosphere, hydrosphere and biosphere.
Humans can reduce this damage by saving energy, using renewable energy, planting trees, saving water, reducing waste, reusing materials and recycling. Mission LiFE encourages eco-friendly habits that help restore Earth’s balance.
Case-Based Questions from Earth as a System: Energy, Matter, and Life
Case-based questions test application and interpretation. Read the case carefully, identify the sphere or cycle involved, then answer each sub-part directly.
Q24. Case-Based Question: Melting Glaciers and Coastal Cities
A rise in atmospheric temperature accelerates the melting of Himalayan glaciers and polar ice. Rivers may receive more meltwater initially, but long-term ice loss can disturb river flow. Sea levels may rise and threaten low-lying coastal cities.
(a) Which Earth sphere includes glaciers?
Glaciers are part of the cryosphere.
(b) Which sphere receives water after glaciers melt?
The hydrosphere receives meltwater through rivers, lakes and oceans.
(c) How can melting ice affect the biosphere?
It can damage habitats, disturb river ecosystems, threaten coastal organisms and affect human settlements.
(d) Why are coastal cities at risk?
Sea-level rise can cause flooding, erosion, saltwater intrusion and damage to infrastructure.
Q25. Case-Based Question: Urban Heat Island
A city has many concrete buildings, asphalt roads and fewer trees. During summer nights, the city remains warmer than nearby rural areas.
(a) What is this effect called?
It is called the urban heat island effect.
(b) Why do concrete and asphalt increase city temperature?
They absorb and retain solar radiation, then re-radiate heat at night.
(c) Why are rural areas comparatively cooler?
Rural areas have more vegetation, shade and plant transpiration.
(d) Give one way to reduce urban heat.
Planting trees, increasing green spaces and using reflective surfaces can reduce urban heat.
Q26. Case-Based Question: Fertilisers and Algal Bloom
A farming region uses excess fertilisers. During rain, fertiliser runoff enters a nearby lake. After a few days, thick green algae cover the water surface and many fish die.
(a) What is this process called?
This process is called eutrophication.
(b) Which nutrients mainly cause algal blooms?
Excess nitrates and phosphates cause algal blooms.
(c) Why do fish die during eutrophication?
Decomposing algae use up dissolved oxygen, leaving less oxygen for fish.
(d) Which biogeochemical cycle is disturbed here?
The nitrogen cycle is disturbed because excess nitrogen enters the water body.
Q27. Case-Based Question: Warming Arabian Sea and Monsoon
The Arabian Sea becomes warmer than usual. More water evaporates and the moisture content in the atmosphere changes. Some regions receive heavy rainfall while others face dry conditions.
(a) Which two Earth spheres interact first in this case?
The hydrosphere and atmosphere interact first.
(b) Why does warmer sea water increase evaporation?
Higher temperature gives water molecules more energy, so more water changes into vapour.
(c) How can this affect India’s monsoon?
It can disturb rainfall patterns, causing floods in some areas and droughts in others.
(d) Which human activity can intensify such warming?
Burning fossil fuels can increase greenhouse gases and intensify global warming.
Numerical Questions on Solar Radiation and Insolation
Chapter 13 includes solar energy calculation based on insolation. Use the formula: Energy = Intensity × Area × Time.
Q28. How much solar energy will be received by a 2 m² area in one hour if the insolation is 1 kW m⁻²?
Given:
Intensity = 1 kW m⁻² = 1000 J s⁻¹ m⁻²
Area = 2 m²
Time = 1 hour = 3600 s
Energy = Intensity × Area × Time
Energy = 1000 × 2 × 3600
Energy = 7,200,000 J
So, the energy received is 7.2 × 10⁶ J.
Q29. If a 1 m² surface receives 3.6 × 10⁶ J of solar energy in one hour, what is the insolation?
Given:
Energy = 3.6 × 10⁶ J
Area = 1 m²
Time = 3600 s
Insolation = Energy ÷ (Area × Time)
Insolation = 3.6 × 10⁶ ÷ (1 × 3600)
Insolation = 1000 W m⁻²
So, the insolation is 1 kW m⁻².
Q30. How much solar energy will be received by a 5 m² area in 30 minutes if the insolation is 1 kW m⁻²?
Given:
Intensity = 1 kW m⁻² = 1000 J s⁻¹ m⁻²
Area = 5 m²
Time = 30 minutes = 1800 s
Energy = Intensity × Area × Time
Energy = 1000 × 5 × 1800
Energy = 9,000,000 J
So, the energy received is 9.0 × 10⁶ J.
Class 9 Science Important Questions List Chapter-Wise