Changes Around Us Physical and Chemical — Question 2

Stitching cloth to a shirt – Cannot be reversed: Once stitched, it is hard to undo without damage. (ii) Twisting of straight string Answer: Twisting of straight string – Can be reversed: The string can be untwisted. (iii) Making idlis from a batter Answer: Making idlis from a batter – Cannot be reversed: The batter cannot be returned to its original form after steaming. (iv) Dissolving sugar in water Answer: Dissolving sugar in water – Can be reversed: Sugar can be recovered by evaporating water. (v) Drawing water from a well Answer: Drawing water from a well – Can be reversed: Water can be returned to the well. (vi) Ripening of fruits Answer: Ripening of fruits – Cannot be reversed: Once ripe, fruits cannot go back to unripe. (vii) Boiling water in an open pan Answer: Boiling water in an open pan – Can be reversed: Evaporated water can be obtained back by condensation. (viii) Rolling up a mat Answer: Rolling up a mat – Can be reversed: The mat can be unrolled. (ix) Grinding wheat grains to flour Answer: Grinding wheat grains to flour – Cannot be reversed: Flour cannot be turned back into grains. (x) Forming of soil from rocks Answer: Forming of soil from rocks – Cannot be reversed: Soil formation is a slow process and cannot form rock back.