Earth as a System Class 9 Science NCERT Solutions

The NCERT Solutions for Class 9 Science Chapter 13 Earth as a System Energy, Matter, and Life cover every question from the Revise, Reflect, Refine exercise, according to the latest 2026-27 syllabus. This page solves all 15 questions in plain, step-by-step language. Each answer is based on the idea that the Earth is one connected system of five spheres, held together by biogeochemical cycles and the greenhouse effect. You get albedo, winds, ocean currents, the water, carbon, nitrogen and oxygen cycles, and climate change in one place.

These NCERT Solutions for Class 9 Science Chapter 13 are prepared by subject experts, based on the 2026-27 NCERT Exploration textbook, and checked against the official NCERT answer key.

• 15 solved questions from the Revise, Reflect, Refine exercise, covering Earth's spheres, the four biogeochemical cycles, and the greenhouse effect.
• Every answer names the concept used first, then explains the reasoning in short steps, so nothing is skipped.
• Based on the new 2026-27 NCERT Exploration textbook, with an expert method added to each question.

Earth as a System Class 9 Explained in Simple Language

Source: Magnet Brains on YouTube

This video explains the biogeochemical cycles and the Earth system before you start the exercise. Watch it once, then use the step-by-step solutions below to practise each question. The video and these solutions together cover Earth's five spheres, the water, carbon, nitrogen and oxygen cycles, and the greenhouse effect.

How Collegedunia's Class 9 Earth as a System NCERT Solutions Help You

Chapter 13 is more about clear ideas than about numbers. Most questions ask you to reason, not to calculate. These solutions make each question easy to understand and easy to score.

• 2026-27 NCERT alignment: Every answer is based on the new Exploration textbook and the official NCERT answer key.
• Concept first: Each solution begins by naming the exact idea it uses, such as albedo, a biogeochemical cycle, or the greenhouse effect.
• Reasoning shown in steps: Long-answer questions are broken into short steps, so you never lose method marks.
• Expert method added: A second, simpler way to think about each question is given below the main solution.

Earth's Five Spheres and How They Interact in Class 9 Science

The chapter treats the whole Earth as one connected system. It has five parts, called spheres, that constantly swap energy and matter. Knowing these five spheres makes the rest of the chapter easy.

Energy from the Sun drives the whole system. Uneven heating of the Earth, measured by albedo, sets up the winds and ocean currents that move heat around the planet.

Revise, Reflect, Refine Exercise Breakdown for Class 9 Science Chapter 13

The Chapter 13 exercise is called Revise, Reflect, Refine and has 15 questions. The table shows what each question tests, so you can plan your practice.

Start with the definition and MCQ questions, then move to the cycle diagrams. All 15 fully solved answers, with an expert method for each, are given lower down this page.

Biogeochemical Cycles in Class 9 Science: Water, Carbon, Nitrogen and Oxygen

A biogeochemical cycle is the movement of a nutrient in a loop between the living (biotic) and non-living (abiotic) parts of the Earth. The same atoms are used again and again, so nothing runs out. Four cycles are tested in this chapter.

• Water cycle: water moves through evaporation, condensation, rain, and flow back to the sea.
• Carbon cycle: carbon moves between air, plants, animals and fuels through photosynthesis, respiration and burning.
• Nitrogen cycle: nitrogen gas is fixed into the soil, used by plants, and returned to the air by bacteria.
• Oxygen cycle: oxygen is released by photosynthesis and used up in respiration and burning.

These cycles are the heart of the chapter. No new atoms are ever made; the cycles only move the same matter around, keeping ecosystems running.

The Greenhouse Effect and Climate Change in Class 9 Science

The greenhouse effect is what keeps the Earth warm enough for life. Without it, the planet would be far too cold. Questions 13 to 15 are all built on this idea.

• Sunlight passes through the air and warms the land and oceans.
• The warm surface gives off heat as infrared radiation.
• Greenhouse gases like carbon dioxide, methane and water vapour trap part of this heat.
• Burning fuels adds extra carbon dioxide, which traps more heat and drives climate change.

The Keeling curve in Figure 13.14 shows carbon dioxide rising year after year. This rise is the main human impact on the Earth system that the chapter asks you to explain.

Earth as a System Weightage for the Class 9 Science Exam

Chapter 13 sits in the biology and environment part of Class 9 Science. It carries steady marks each year, mostly through reasoning and diagram questions. The table compares it with nearby chapters.

Because the diagrams and cycles repeat every year, this chapter is one of the safest places to score full marks with a little practice.

Common Mistakes Students Make in the Earth as a System Chapter

Solved Example: Naming the Energy and Matter Flow in a Biogeochemical Cycle

Explain how carbon moves from the air into an animal and back again. This follows the same reasoning pattern used in Questions 10 to 12 of the exercise.

1. Carbon enters plants: green plants take in carbon dioxide from the air and fix it into food during photosynthesis.
2. Carbon moves to animals: animals eat the plants, so the carbon passes into their bodies.
3. Carbon returns to the air: animals and plants release carbon dioxide during respiration, and decay returns the rest.
4. The loop closes: the same carbon atoms are used again, which is why it is called a cycle.

Every cycle question in this chapter follows this same pattern: name the store, name the process that moves the matter, and show how it returns.

How to Use the Class 9 Earth as a System Solutions Most Effectively

Use a simple three-step routine so the cycles and diagrams stay in your memory until the exam.

• Learn the five spheres and four cycles first, and draw each cycle once from memory.
• Attempt each question yourself, then compare with the step-by-step solution below.
• Redo the reasoning questions you got wrong two days later, without looking at the answer.

Pair this page with the chapter notes and handwritten notes for quick revision before the exam.

NCERT Class 9 Science Chapter 13 Other Study Resources

Use the other free resources for the same chapter alongside these solutions.

NCERT Solutions for Class 9 Science: All Chapters

Find the step-by-step NCERT Solutions for the other Class 9 Science chapters below.