Answer the following questions :
1. Which of these changes, do you think can be reversed.
| Change | Can be reversed (Yes/no) |
| Raw egg to boiled egg | |
| Balter to Idli | |
| Wet clothes to dry clothes | |
| Wollen yarn to knitted sweater | |
| Grains to its flour | |
| Cold milk to hot milk | |
| Straight string to coil string | |
| Bud to flower | |
| Milk to paneer | |
| Cow dung to biogas | |
| Stretched rubber band to its normal size |
|
| Solid ice cream to molten Ice – cream |
Ans :
| Change | Can be reversed (Yes/no) |
| Raw egg to boiled egg | No |
| Balter to Idli | No |
| Wet clothes to dry clothes | Yes |
| Wollen yarn to knitted sweater | Yes |
| Grains to its flour | No |
| Cold milk to hot milk | Yes |
| Straight string to coil string | Yes |
| Bud to flower | No |
| Milk to paneer | No |
| Cow dung to biogas | No |
| Stretched rubber band to its normal size | Yes |
| Solid ice cream to molten Ice – cream | Yes |
2. Boojho has often noticed that road construction workers heat a black material (tar) for repairing a road. He wants to know whether the change caused in tar by heating, is reversible.
Ans: Yes, the change caused in tar by the by the heating in reversible.
3. What change has taken place in iron, on being heated.
Ans: On being heated, the iron becomes soft and in beated into a desired shape.
4. How the iron blade is fired to there wooden handle which is shown below.
Ans: The iron blade of these tools has a ring which is slightly smaller than the wooden handle. The ring is heated and it becomes slightly larger in size. Now the handle easily fits into the ring when the ring cools down it contracts and fits tightly on to the handle.
5. How the metal rim is fired on a wooden wheel of a cart.
Ans: The metal rim is made slightly smaller than the wooden wheel. On heating, the rim expands and fits on to the wheel. Cold water is then poured over the rim, which contracts and fits tightly onto the wheel.
Choose the correct answer:
1. A seed sprouts, grow as a tree, this process is reversible.
a) True b) False
2. When a paper is burnt it becomes ashes, it is not reversible.
a) True b) False
3. The incense stick burns to produce ash and some gases. It is reversible .
a) True b) False
4. Cooked rice is not reversible.
a) True b) False
5. The river water mixed in the sea is not reversible.
a) True b) False
6. Papers are made from trees, it is reversible.
a) True b) False
7. Sugar mixed with water is reversible.
a) True b) False
8. An apple juice is reversible as an apple.
a) True b) False
Answers :
1. False 2. True 3. False 4. True 5. True 6. False 7. True 8. False.