end point
/ END point /
Picture stirring sugar into tea and watching for the moment the colour-changing strip in your cup finally flips shade — that visible flip is your signal to stop. The end point of a titration is exactly that: the observable change that tells you to stop adding titrant.
Precisely, the end point is the point during a titration at which a detectable signal — most often a colour change from an indicator, but sometimes a sudden jump in pH or electrical reading — tells the analyst the reaction appears finished. You record the titrant volume at this moment.
It matters because the end point is what you can actually see or measure, standing in for the true completion of the reaction. The catch is that the visible end point seldom falls exactly at the true completion; the small gap between them is the titration error, which good method design keeps tiny.
In an acid-base titration, the end point arrives when one extra drop of base turns the phenolphthalein indicator from colourless to a faint, lasting pink — the analyst stops and reads the burette there.
The end point is the signal you see; it stands in for the true finish.
Do not confuse the end point with the equivalence point. The equivalence point is the exact, ideal moment the reaction is stoichiometrically complete; the end point is the real, observed moment you stop — chosen to land as close to it as possible.