Question

1. A drawing sheet changes when you draw a picture on it . can you reverse this change ?


2. GIVE examples to explain the difference between changes that can or cannot be reversed ?


3. A thick coating of a paste of plaster of of Paris (pop) is applied over the bandage on a fractured bone. It becomes hard on drying to keep the fractured bone immbolised . Can you change in a
POP be reversed?





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Answer 1

Answer:

1.No, we cannot get the same drawing sheet back if we draw the picture on it with pen or paint. It can be reversed by rubbing the picture with eraser if drawn with a pencil

2.(i) Folding of a paper is a reversible change because paper can be unfolded to get it back.

(ii) Burning of paper is an irreversible change because we cannot get back the paper after burning it.

(iii) Mimosa (touch-me-not) leaves collapse on touching and open up on removing finger. Hence, it is a reversible change.

(iv) Growth of a plant is irreversible since it cannot be reversed.

3.No, once the plaster is dried, it becomes hard and cannot be reversed back to paste form.

Answer 2

1. No, we cannot get the same drawing sheet back if we draw the picture on it with pen or paint. It can be reversed by rubbing the picture with eraser if drawn with a pencil.

2. Melting of ice is a reversible change. ... When ice cubes are kept at room temperature, they turn into water after some time. On the other hand, burning of a piece of paper is an irreversible change.

3. No, the change in plaster of Paris cannot be reversed. When water is added to POP, it undergoes a chemical change.