Mention whether the following changes are reversible pr irreversible (1) Souring of milk (ii) Dissolving salt in water (II) Boiling of an egg ierewesible (iv) Ironing of shirt (v) Ripening of banana (vi) Burning of paper
Answers
Souring of milk - Irreversible
Souring of milk is the process in which curd is formed. The physical and chemical characteristics of curd is completely different from that of milk and therefore it is an irreversible change.
Dissolving salt in water - Reversible
When salt is dissolved in water, a salt solution is formed which is homogeneous in nature. If we require the salt and water back, we can get it by evaporation followed by condensation which gives us the salt and water separated. So, it is a reversible change.
Boiling of egg - Irreversible
When an egg is boiled, the outer membrane becomes a white, soft and thick covering while the yolk solidifies. It cannot be reversed back into a raw egg. Therefore this change is irreversible.
Ironing of shirt - Reversible
Ironing of shirt is a reversible change. Once we wear an ironed shirt, it crumbles and it needs to be ironed again after a wash to make it straight and stiff.
Ripening of banana - Irreversible
Once a banana ripens, there is no way in which it can be reversed back into its raw form. Henceforth, it is an irreversible change.
Burning of paper - Irreversible
When a paper is burned, it changes into black ash. We cannot turn the black ash back into paper. So, it can be classified as an irreversible change.
➡ Mostly all physical changes are reversible. An example of an exceptional case is that of cutting a tree - the physical characteristics remain the same but the change cannot be reversed.
➡ Chemical changes are usually irreversible in nature but some chemical changes can be reversed with the help of some specific acids and bases. For example, rust can be removed from iron objects by careful cleaning with vinegar (acetic acid).