Classify the following changes into reversible and irreversible changes:
a) Stretching of a spring
b) Dissolving sugar in water
c) Cooking of food
d) Souring of milk.
Answers
Answer:
a. reversible
b.irreversible
c.irreversible
d.irreversible
a) Stretching of a spring:
Ans. Reversible change
Exp. When we a stretch a spring and remove the force exerted, the spring goes back to the normal position. That is, it comes back to its actual shape. As its previous shape can be procured even if a force is exerted to change the shape, the change observed is reversible.
b) Dissolving sugar in water
Ans. Reversible change
Exp. When we put a certain amount of sugar into water, we get a sugar solution. We can get back the sugar and water through the processes of evaporation and condensation. As we can get the sugar nd water separately, it is a reversible change.
c) Cooking of food
Ans. Irreversible change
Exp. When we cook food, a chemical change takes place where we put in heat energy and even a change in taste is observed. We cannot put the sources we put into it back. Hence the change observed is irreversible.
d) Souring of milk
Ans. Irreversible change
Exp. When souring of milk occurs, a change in the taste is observed and the milk cannot be used. We cannot have the milk back as it is. Hence the change is irreversible.
Reversible Changes:
Those changes in which we can get back the resources we put in an experiment as they are, are known as reversible changes. The only changes will be in the state of matter, shape etc.
Irreversible Changes:
Those changes in which we cannot get back the resources we put in an experiment as they are, are known as irreversible changes. A new substance is formed in an irreversible change. A change in colour, taste etc. can be observed.