So if we take a look at this example question, it says are the following processes reversible or irreversible? Remember we tend to connect to the term reversible physical changes and what physical changes we can undergo the change without changing the identity of the original material. Irreversible changes we connect to chemical changes.
So if we take a look here, it says first we're dissolving sugar and water. Remember we said earlier when you're dissolving your solute then that represents a physical change. Because all I'd have to do here is boil off the water and what will be left in my pot would be the original sugar. So this would be an example of a physical change, which would mean it's reversible.
Next, adding lemon juice to cabbage juice. It causes the color to transition from purple to deep red. We said earlier that color change is an example of a chemical change and because it's a chemical change, it would be irreversible. Adding citrus to baking powder. Now this one may not be as clear. Some people may not have done this little homec type of experiment, but if you take citrus like lemon, and you squirt it on some baking powder, it's going to start to fizz and bubble. That's because an actual chemical reaction is being done. Now, if a chemical reaction is being done, that is an example of a chemical change. And if it's a chemical change, it's an irreversible change.
Lastly, if we have the mixing of oil in water, we've talked about before that oil and water don't mix, so they don't really interact. That means they hold on to their individual identities without really changing. We have our original substances being themselves, and because we have original substances, that's a physical change. We could also say earlier that mixing we said of substances is a prime example of a physical change. So this would be reversible.
So just remember the key terms that we covered when discussing physical changes and chemical changes. Remember that these physical changes can be seen as reversible changes and are chemical changes can be seen as irreversible changes.