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GCSE Combined Science · key term
A chosen observable stage at which a measurement is stopped, such as when a cross can no longer be seen through a reaction mixture.
Used by OCR
Specification B1.2c, C5.1a, B3, C5 · Biology Paper 1, Biology Paper 2, Chemistry Paper 1, Chemistry Paper 2, Physics Paper 1, Physics Paper 2
An observable change used to decide when a reaction has reached a chosen stage, such as when starch is no longer detected by iodine.
Revise: Investigating Enzymatic ReactionsThe endpoint is the first sample that stays orange-brown, showing that starch is no longer detected.
A shorter endpoint time means a faster reaction. A graph of time against temperature or pH therefore has a minimum where a graph of reciprocal time has a maximum.
If a reaction has not reached the endpoint when observations stop, record 'greater than' the observation time. Do not treat that time as an exact endpoint or assume the rate is zero.
The disappearance of a cross is a chosen endpoint, not evidence that the reaction has finished.
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An observable point used to stop timing a reaction, such as the first sample that no longer turns iodine blue-black.
A chosen, observable point at which timing stops, such as collecting a fixed volume of gas or a cross becoming hidden.
Specification B3, C5 · Biology, Chemistry, Physics, Combined Science
The point in a titration at which the indicator changes colour, signalling when to stop adding solution.
Revise: Neutralisation and TitrationThe observed colour change is called the endpoint.
A defined, observable stage used to stop timing, such as a cross disappearing or a colour disappearing.
The point at which a specified observable change has occurred, such as an iodine test no longer detecting starch.
A defined observable point at which a measurement is stopped, such as a cross becoming invisible through a reaction mixture.
