changes around us

Q.No 1. To walk through a Waterlogged area,you usually shorten the length of your dress by folding it. Can this change be reversed?

Ans. Yes this change can be reversed. 

Q.No 2. You accidentally dropped your favourite toy and broke it. This is a change you did not want. Can this change be reversed?

Ans. No, this change can not be reversed. 

Q.No 3. Some changes are listed in the following table. For each change ,write in the blank column. Whether the change can be reversed or not.

Ans. 1. The sawing of a piece of wood. Ans No

2. The melting of ice candy .Ans. Yes

3.Dissolving sugar in water .Ans. yes

4.The cooking of food. Ans. No

5.The ripening of a mango. Ans. No

6.souring of milk. Ans. No

Q.No 4. A drawing Sheet changes when you draw a picture on it.Can you reverse this change?

Ans. If the picture is drawn with a pencil, then it can be erased, hence the change can be reversed  ,but if the picture can be drawn with the colours, the change can not be reversed. 

Q.No 5. Give examples to explain the difference between changes that can or cannot be reversed. 

Ans. Example of reversible changes. 

1. Filling of water in glass. 

2.opening and closing of doors. 

3. Dissolving of sugar in water. 

4.streching of rubber band.

5. Melting of candles or ice.

Examples of not reversible changes. 

1. Burning of match sticks. 

2. Batter of idli.

3. Bud of flower.

4. Cowdung to biogas. 

5.curdling of milk. 

Q.No 6. A thick coating of a paste of plaster of Paris is applied over the bandage on a fractured bone. It becomes hard on drying to keep the fractured bone immobilized. Can the change in POP be reversed?

Ans. No, the change in Plaster of Paris can not be reversed. 

Q.No 7. A bag of cement lying in the open gets wet due to rain during the night. The next day the sun shines brightly. Do you think the changes, which have occurred in the cement, could be reversed?

Ans. No,the changes which have occurred in the cement cannot be reversed.