Notes on Measurement and Procedural Errors

Procedural and Measurement errors

Procedural errors

These are errors inherent in the procedure. In other words, EVEN IF you carried out the experiment absolutely as written, and didn’t make any mistakes, these errors would still be there.

There are some that come up again and again, for example:

|Error |Nature of experiment |Problem with procedure |Possible solution |

|Gas escaping |Anything which involves measuring|“mix the two substances and quickly |Anything that keeps the two substances |

| |gas volumes. |replace the bung” – quickly is never |separate until the bung has been replaced, |

| | |quite quick enough! |e.g. put one chemical in a small test tube, |

| | | |shake to mix. |

|Heat loss |Anything which involves measuring|A lid isn’t used, or the container isn’t |Use a lid and/or insulate the beaker! |

| |temperature change. |insulated. | |

|Mass errors |Particularly applies to | The substance decomposes on | Heat gently, for a specified time, |

| |percentage water of |heating (so final mass is less than |possibly using an oven with a thermostat (but|

| |crystallisation experiments but |expected)… |NOT a water bath!). |

| |could also apply to e.g. thermal |or not all of the water has been removed |Repeat the ‘heat, cool, weigh’ cycle until a |

| |decomposition...