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A bench in the sun feels warm. No fire is anywhere near it.

This is Chapter 13 of your Class 9 book, Exploration. It is called Earth as a System: Energy, Matter, and Life.

What you will learn

• One thing arrives — sunlight is the main energy source.
• What arrives and what leaves — the ground sends heat out.
• Not all the same light — three kinds of light, three jobs.
• Heated unevenly — slant and snow decide how much the ground keeps.
• Matter goes round — water moves round the water cycle.
• Life is in the loop — carbon goes round through living things.
• One system — five spheres of Earth affect one another.

Quick catch-up

These help, though none is required.

• Radiation — heat can cross empty space with nothing carrying it.
• The blanket of air — air keeps day and night close in temperature.
• A warm patch of air rises — and pulls in cooler air.
• Decomposers — living things that return a dead plant's material to the soil.

One rule before anything else

Every lab in this track is a simulation. Every number in a lab is made up, or a round number. Never look at the Sun, and never point anything at it.