Question

iv) Rohan tore a sheet of paper into pieces
and then burnt them. Identify the
irreversible change taking place in the
process.
(a) Tearing the sheet into pieces
(b) Burning the pieces

Answer 1

Required Answer:-

(a) Tearing the sheet into pieces $:$

It is a kind of physical and irreversible change. It is because we can't reverse the process and get the full sheet of paper back. But it is still a paper, the chemical composition hasn't changed. Only the physical property i.e. shape and size have changed.

(b) Burning the pieces:

It is a kind of chemical and irreversible change. It is because the chemical composition of the paper have changed. The paper is now changed into ashes. Also, we can't reverse the process and get the paper back.

Answer 2

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✠ ɢɪᴠᴇɴ ᴄᴏɴᴅɪᴛɪᴏɴs:–

• Rohan tore a sheet of paper into pieces and then burnt them.

❶ Tearing the sheet into pieces:–

This type of change is a physical irreversible change. Let us recall what a physical change is. A physical change is a type of change in which no new substances are formed and the change can generally be reversed by the reversing the conditions. When we tear the sheet obviously no new substances are formed.

Some other examples of physical changes:– Cutting of wood, melting of ice, etc.

➋ Burning the pieces:–

This type of change is a chemical irreversible change. Let us recall what a chemical change is. A chemical change is a type of change in which the substance's chemical composure changes and new substances are formed. This type of change cannot be reversed by reversing the conditions. When we burn paper Carbon Dioxide (CO₂) is formed.

Some other examples of chemical changes:–

Burning of wood, rusting of iron, etc.