NCERT Solutions For Class 6 Science Chapter – 6
Q1. To walk through a waterlogged area, you usually shorten the length of your dress by folding it. Can this change be reserved ?
Answer:-
Yes, it can be reversed by unfolding the dress.
Q2. You accidentally dropped your favourite toy and broke it. This is a change you did not want. Can this change be reversed?
Answer:-
No this change (breaking of toy) cannot be reversed.
Q3. Some changes are listed in the following table. For each change write n the blank column whether the change can be reserved or not.
Q4. A drawing sheet changes when you draw a picture on it. Can you reserves this change?
Answer:-
We cannot get fresh drawing sheets once a picture is drawn on it with paint/oil or water. However, we can reserve the change, if soft pencil is used to draw the picture.
Q5. Give examples to explain the difference between changes that can or not cannot be reversed.
Answer:-
Examples of reversible and irreversible changes
| Reversible changes | Irreversible changes |
| Glowing of electric bulb (It glows when switched on and becomes dark when switched off.) | Burning of paper or wood. ( It gives smoke and ash, which can not form paper or wood again). |
| Distillations of liquid: | Rusting of iron. (Rust cannot be changed into iron again.) |
| Sublimation | Making of curd from milk. |
| Collapsing of mimosa ( touch me not) leaves on touching and opening up on removing the finger. | Growth of plants and animals. |
Q6. 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 immobilised. Can you change in POP be reversed ?
Answer:-
No. The change in POP cannot be reversed since it is a chemical change.
Q7. 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?
Answer:-
No, these are irrversible chemical changes.