Question Bank — Earth as a System: Energy, Matter, and Life

NCERT Class 9 Science · Chapter 13 · CBSE Board Pattern

Class 9 Science Chapter 13 Question Bank CBSE Board Pattern

QUESTION BANK

Chapter 13: Earth as a System: Energy, Matter, and Life
CBSE Class 9 Science (NCERT)

Section A — MCQs (10 questions, 1 mark each)

  1. The main source of energy that powers life on Earth is
    (a) Earth’s interior heat
    (b) Solar radiation
    (c) Chemical reactions in rocks
    (d) Cosmic rays

  2. Which of the following surfaces has the highest albedo?
    (a) Black soil
    (b) Ocean water
    (c) Snow
    (d) Crushed rock

  3. The layer of the atmosphere where almost all weather phenomena occur is
    (a) Stratosphere
    (b) Troposphere
    (c) Mesosphere
    (d) Thermosphere

  4. The solar constant is approximately
    (a) 1.4 kW m⁻²
    (b) 1.0 kW m⁻²
    (c) 3 × 10⁸ m s⁻¹
    (d) 6.5 °C km⁻¹

  5. Assertion (A): Excess carbon dioxide in the atmosphere leads to global warming.
    Reason (R): Carbon dioxide is a greenhouse gas that traps outgoing infrared radiation from the Earth’s surface.
    (a) Both A and R are true and R is the correct explanation of A.
    (b) Both A and R are true but R is not the correct explanation of A.
    (c) A is true but R is false.
    (d) A is false but R is true.

  6. Planetary winds are deflected to the right in the Northern Hemisphere due to
    (a) Uneven heating of land and water
    (b) Rotation of the Earth
    (c) Presence of ozone layer
    (d) High albedo of polar regions

  7. Assertion (A): Ocean currents help in reducing temperature differences between the equator and the poles.
    Reason (R): Warm currents transport heat from equatorial regions towards the poles.
    (a) Both A and R are true and R is the correct explanation of A.
    (b) Both A and R are true but R is not the correct explanation of A.
    (c) A is true but R is false.
    (d) A is false but R is true.

  8. The process by which atmospheric nitrogen is converted into ammonia by bacteria such as Rhizobium is called
    (a) Nitrification
    (b) Denitrification
    (c) Nitrogen fixation
    (d) Ammonification

  9. Which of the following is not a greenhouse gas?
    (a) Carbon dioxide
    (b) Methane
    (c) Nitrogen
    (d) Water vapour

  10. The ozone layer is located in the
    (a) Troposphere
    (b) Stratosphere
    (c) Mesosphere
    (d) Exosphere

Section B — Very Short Answer (6 questions, 2 marks each)

  1. Define insolation. How is it different from the solar constant?
  2. What is albedo? Give one example each of a high-albedo and a low-albedo surface.
  3. Name the five spheres of the Earth. Which sphere includes the Himalayan glaciers?
  4. Differentiate between valley breeze and mountain breeze (one point each).
  5. What is eutrophication? How is it caused by human activities?
  6. State any two roles of the atmosphere in protecting life on Earth.

Section C — Short Answer (5 questions, 3 marks each)

  1. Explain, with the help of a flow chart, how a disturbance in the cryosphere can affect the hydrosphere and biosphere.
  2. Describe the formation of equatorial low-pressure belt and sub-tropical high-pressure belts.
  3. How does the Earth’s spherical shape and latitude cause uneven heating of the Earth’s surface?
  4. Explain the processes of nitrogen fixation, nitrification and denitrification in the nitrogen cycle.
  5. What is the urban heat island effect? How do building materials contribute to it?

Section D — Long Answer (3 questions, 5 marks each)

  1. Describe the water cycle with a labelled diagram. Explain how climate change affects different stages of the cycle and links the cryosphere, hydrosphere, atmosphere, geosphere and biosphere. (Labelled diagram required)
  2. (a) Calculate the solar energy received by a 2 m² area in 2 hours if the insolation at the Earth’s surface is 1 kW m⁻². Show all steps.
    (b) How does this energy compare with the example given in the chapter for 1 m² in one hour? (Multi-step numerical)
  3. Explain the carbon cycle with the help of a schematic diagram. Discuss the fast and slow cycles and the impact of human activities on the atmospheric carbon dioxide concentration.

Section E — Case/Source-Based (2 questions, 4 marks each)

Case 1

Read the passage and answer the questions that follow:
“Less snowfall in winters for a few years may lead to less water in the lake in summers, resulting in less water to support the growth of grass. On a large scale, warmer Arabian Sea water leads to more evaporation, causing fluctuations in the southwest monsoon. This may accelerate the melting of glaciers and polar ice, raising sea levels that threaten coastal cities.”

  1. Identify the spheres involved in the above scenario and name them. (1 mark)
  2. How does warming of the Arabian Sea affect the hydrosphere and atmosphere? (1 mark)
  3. What long-term effect on the biosphere is mentioned in the passage? (1 mark)
  4. Suggest one way in which disturbance in one sphere leads to changes in others, using the example of glaciers. (1 mark)

Case 2

Read the passage and answer the questions that follow:
“Dark surfaces absorb more sunlight while light-coloured surfaces reflect more. Snow and ice have albedo values of 0.80–0.90. This makes polar regions very cold. Human activities such as burning fossil fuels have raised atmospheric CO₂ from 315 ppm (1960) to 420 ppm (2025), intensifying the greenhouse effect.”

  1. Define albedo and state why polar regions remain cold. (1 mark)
  2. What is the significance of the increase in CO₂ concentration shown in the passage? (1 mark)
  3. Name two greenhouse gases mentioned in the chapter besides CO₂. (1 mark)
  4. How can the balance of the carbon cycle be restored according to the chapter? (1 mark)
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Section A

  1. (b)
  2. (c)
  3. (b)
  4. (a)
  5. (a) — Both true, R explains A (greenhouse effect)
  6. (b)
  7. (a) — Both true, R explains A (heat transport)
  8. (c)
  9. (c)
  10. (b)

Section B

  1. Insolation = solar radiation reaching Earth’s surface (1 mark); Solar constant = value at top of atmosphere before absorption/scattering (1 mark).
  2. Albedo = fraction of solar radiation reflected by a surface (1 mark); High: snow/ice; Low: black soil/ocean water (1 mark).
  3. Geosphere, Hydrosphere, Cryosphere, Atmosphere, Biosphere (1 mark); Cryosphere (1 mark).
  4. Valley breeze: warm air rises from slopes during day (1 mark); Mountain breeze: cool air sinks from slopes at night (1 mark).
  5. Excessive algal growth due to nutrient runoff depleting oxygen (1 mark); Overuse of fertilisers (1 mark).
  6. Absorbs harmful UV (ozone layer) (1 mark); Traps outgoing heat (greenhouse gases) (1 mark).

Section C

  1. Flow chart linking cryosphere → hydrosphere → biosphere with example of reduced snowfall (definition 1, linkage 1, example 1).
  2. Intense heating at equator → rising air → equatorial low; sinking air at 30° N/S → sub-tropical high (3 points).
  3. Spherical shape concentrates radiation near equator, spreads at poles; latitude determines angle of incidence (3 marks).
  4. Nitrogen fixation (Rhizobium), nitrification (Nitrosomonas/Nitrobacter), denitrification (Pseudomonas) (1 mark each).
  5. Cities warmer than rural areas due to concrete/asphalt absorbing and re-radiating heat (3 marks).

Section D

  1. Labelled diagram of water cycle (evaporation, condensation, precipitation, transpiration, runoff, groundwater) — 3 marks; Climate-change linkages across five spheres — 2 marks.
  2. (a) E = 1 kW m⁻² × 2 m² × 7200 s = 1.44 × 10⁷ J (full working) — 3 marks; (b) Comparison with 3.6 × 10⁶ J example — 2 marks.
  3. Schematic carbon cycle (photosynthesis, respiration, fossil fuels, ocean exchange) — 3 marks; Fast/slow cycles + human impact (CO₂ rise) — 2 marks.

Section E

Case 1

  1. Cryosphere, hydrosphere, atmosphere, biosphere (any two) — 1 mark.
  2. Increased evaporation → monsoon variability — 1 mark.
  3. Habitat loss / threat to coastal cities — 1 mark.
  4. Melting glaciers → sea-level rise → coastal flooding — 1 mark.

Case 2

  1. Fraction reflected; high albedo of snow/ice reflects most radiation — 1 mark.
  2. Intensified greenhouse effect/global warming — 1 mark.
  3. Methane, water vapour — 1 mark.
  4. Switch to renewables, plant trees, reduce fossil-fuel use — 1 mark.
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All questions are answerable from the NCERT chapter text. Reviewed by GFIS faculty.