Question

Would a change in temperature during a calibration of volumetric glassware experiment (involving a buret and pipet) impact accuracy, precision or both? Explain. What would be the difference if a graduated cylinder was used instead? Explain.

Answer 1

Yes, change in temperature during calibration of volumetric glassware may lesd to the inaccurate result.

If glassware in quite hot condition weight will be less than actual. Because when glassware attains room temperature it absorbs heat from surrounding, and shows its actual weight.

Ambient temperature effects: It is important to periodically calibrate an instrument at a temperature close to that at which it will be operated. Even when a calibration is performed properly, there are other factors that can affect the accuracy of results. Environmental factors, such as the ambient temperature, can introduce errors that may not be readily evident when testing samples with unknown values. Components, such as electronics, used in an instrument may be affected by changes in operating temperature. If an instrument is calibrated at one temperature and then operated at a significantly different temperature, the temperature-induced error can also degrade the results’ accuracy.

To minimalize problems we can calibrate the glass - that is, measure the real volume of solution delivered or contained - by weighing mass of the water. Weighing can be done with very good accuracy, and knowing water density we can calculate volume of the given water mass. Thus we can determine exact capacity of the glassware. Well, perhaps not the exact capacity, but at least we will know the volume with much higher accuracy than if we assume its nominal value.

To calibrate the glass we need a good analytical balance, and distilled (or DI) water of known temperature. To be sure measurements are correct it is a good idea to keep water, balance and calibrated glassware in the same room long enough to be sure everything have the same temperature. Room doesn't have to be thermostated, although temperature should not change during the calibration process. It also won't hurt to calibrate the glass in the temperature similar to the temperature in which it will be used, to minimalize later effects of the glass and water thermal expansion.