 If you take a balloon and inflate it carefully like this so that it does not explode, you can see it becomes bigger. Now deflate, deflate the balloon. The balloon then comes back to its old state. So this inflation of the balloon and its return to its original state after deflation, this is a type of a reversible change because the substance can be taken back to its original state. Let's look at some more examples. If you take dough and you roll a roti out of it, if you're not satisfied with the shape of the roti that you can make the dough again, it's a reversible change. Again, changes in which substance return to their original state is called a reversible change. You can also think about pulling a rubber band or a spring. When you stretch it, the spring stretches but when you let go, the spring comes back to its original position. That's still a reversible change. Now let's take this dough. You can take this dough and bake a roti out of it. But now you can't go back to the original state. Now you can't go back. This is an irreversible change. Changes in which substance cannot be brought back to the initial state that they were in. And there are many more examples of irreversible change. For example, if you have a balloon and you burst a balloon, you pop it up, then it can't be inflated again. It has already bursted. This will be an irreversible change. Or burning of paper. When you burn a paper, you can't get the paper back. Again, an irreversible change. Similarly, if you're making paneer out of milk, this is again an irreversible change. Once you have the cottage cheese or the paneer, then you can't get milk out of it. Or burning of a candle. Even burning of a candle is an irreversible change because as the candle burns, the height shortens, the height reduces and you can't get back the same height of the candle. Once it has burned completely, these are irreversible changes.