Equivalence point

Okay, imagine you are baking a cake. You have some flour, sugar, baking powder, and eggs. You mix them all together, put them in the oven, and wait for the cake to bake.

Now let's say you want to know exactly how much baking powder to add to the cake so it turns out perfectly. You can measure out different amounts of baking powder and mix them with the other ingredients to see how the cake turns out.

But how do you know when you've added the right amount of baking powder? You could keep guessing and checking, but that would take a long time and might not be very accurate.

Instead, you can use a magical tool called an indicator. An indicator is something that changes color when it's mixed with certain substances. In this case, we can use an indicator that changes color when it's mixed with baking powder.

So you mix some baking powder with the other ingredients and add a drop of the indicator. At first, the mixture is pink. You add more baking powder and mix again. The mixture turns purple. You add even more baking powder and mix again. The mixture turns blue.

Finally, you add some more baking powder and mix again. But this time, something different happens. The mixture turns from blue to pink in just one drop! That's the equivalence point.

The equivalence point is the point at which the indicator changes color completely and permanently. It means you have added exactly the right amount of baking powder to the cake batter. Now you can make the cake knowing that it will turn out perfectly.