A digital callipers may be more accurate than a tape measure but most callipers can only measure distances up to 10 or 20 cm.
Fig. 17 Different measuring instruments are chosen for their accuracy and suitability.
When working in the laboratory some pieces of equipment are more accurate than others. Fig. 18 shows a variety of laboratory glassware. All the items shown can be used to measure the volume of liquids. Choosing the most appropriate instrument will depend on the amount of liquid to be measured and on how accurate and precise the measurement needs to be.
Fig. 18 A variety of glassware is used to measure the volume of liquids.
For example, laboratory pipettes are used to measure small volumes of liquid when an accurate measurement is needed. However, each pipette can only accurately measure one fixed volume (e.g. 25 cm3 100 cm3
up to 100 cm3
Fig. 19 Pipettes accurately measure one set volume.
Activity
1. Place 25 cm3 2. Place 25 cm3 3. Fill a 25 cm3 at the mark.
of water in a 250 cm3 of water in a 100 cm3
beaker. measuring cylinder pipette with water up to the fill mark. Make sure the water level is exactly
4. Hold the pipette over the measuring cylinder and carefully release a single drop of water into the measuring cylinder and then a single drop into the beaker.
Questions 1. What changes can you observe in the level of liquid in each of the three pieces of measuring equipment?
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2. What do your observations tell you about the accuracy of each type? 3. Ask your teacher to show you a volumetric flask. For what type of measurements do you think a volumetric flask would be most appropriate?
). A measuring cylinder is less accurate but a
measuring cylinder can be used for any measurement .
