Activity 5.8 Let us think Table 5.2 Can changes be reversed? Class 7
hardActivity 5.8 Let us think Class 7
Activity 5.8 Let us think Class 7
Table 5.2 Can changes be reversed? (Page 66)
Answer:
| Change | The original state can be brought hack (Yes/No) |
| 1. Melting ice cubes | Yes |
| 2. Chopping vegetable | No |
| 3. Boiling water | Yes |
| 4. Making popcorn from corn | No |
| 5. Cutting a piece of paper | No |
| 6. Writing on a paper with ink pen | No |
| 7. Burning wood | No |
| 8. Drying wet clothes | Yes |
| 9. Ripening of fruits | No |
| 10. Generation of electricity from water | No |
| 11. Cooking of food | No |
| 12. Lightening of electric bulb | Yes |
Question 1.
Can you think of some other desirable changes happening around you? Class 7
Answer:
Digestion of food, photosynthesis, water purification (chlorination), formation of flower into fruit, formation of seed into plant, formation of halwa, soup.
Question 2.
Have you seen heaps of sand, soil, and stones lying at the base of mountains as shown in Fig. 5.10 (a) (see textbook) ? These are called sediments. How have these formed? Class 7
Answer:
These are formed by physical changes that break up large rocks into smaller pieces. Temperature changes due to climatic conditions, growing roots of trees, and even freezing of water within cracks in the rocks can cause them to break.