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Q2 (Medium): Predict which of the following changes can be reversed and which cannot be reversed: Stitching cloth to a shirt, Twisting of straight string, Making idlis from a batter, Dissolving sugar in water, Drawing water from a well, Ripening of fruits, Boiling water in an open pan, Rolling up a mat, Grinding wheat grains to flour, Forming of soil from rocks.
Answer:
We have studied that
physical changes
are usually
reversible
while
chemical changes
are usually
irreversible
. This is why we can classify them.
Reversible Changes:
- Twisting straight string - can be untwisted
- Dissolving sugar - can evaporate water back
- Drawing water - can put water back
- Rolling up mat - can unroll easily
- Boiling water - steam can condense back
Irreversible Changes:
- Stitching cloth - cutting damages original cloth
- Making idlis - batter undergoes chemical change
- Ripening fruits - chemical changes in fruit
- Grinding wheat - physical structure permanently changed
- Forming soil - rocks break down permanently
