Q1.
List some features of the Earth that we often take for granted, but are interesting and important to us. Write them in Table 13.1. We have filled in a few for you.
Answer
Here is Table 13.1 completed. The two filled rows are the book's; the rest are features you can add, each with the reason it is remarkable.
| S.No. | Interesting feature of the Earth | Why it is remarkable |
|---|---|---|
| 1. | The air we breathe doesn't fly off and disappear into space. | Gas particles move freely and gases have no fixed volume (Chapter 7), yet Earth's gravity is strong enough to hold them. |
| 2. | We can stand on the ground held by gravity (Chapter 5), but our heart can pump blood up to our head. | Gravity is strong enough to keep us down, weak enough that a fist-sized muscle can push blood upwards against it. |
| 3. | Water is found as ice, as liquid and as vapour — all on the same planet at the same time. | Earth's temperature sits right across water's freezing and boiling points, which is why rivers, clouds and glaciers can all exist together. |
| 4. | The Sun does not burn us, even though its light travels straight to us. | The ozone layer absorbs the harmful ultraviolet part, and the magnetic field turns away high-energy particles. |
| 5. | Day follows night with almost the same length of daylight in a given season, year after year. | Earth's spin is steady and its orbit nearly circular, so heat arriving does not swing wildly. |
| 6. | Rain falls as fresh water even though most of Earth's water is salty. | Evaporation leaves the salt behind, so the water cycle keeps refilling rivers, lakes and groundwater with usable water. |
| 7. | Dead leaves and animals do not pile up forever. | Decomposers break them down and return nitrogen and potassium to the soil for the next generation of plants. |
Check it yourself: A good entry for this table is something you would never notice until it stopped. Ask of each item — 'what exactly is holding this steady?' If you can name the reason, the row is worth writing down.