Practice Technique for Graduated Cylinder,

Volumetric Pipet, and Volumetric Flask

Before we start comparing the different measuring tools, we will practice and

demonstrate to our lab partners that we can appropriately apply these

techniques.

For the graduated cylinder add a random amount of liquid and record the

volume. Have everyone at your lab bench do the same without communicating.

Now read the volumes on all the graduated cylinders. Compare your recorded

results with the other people in your lab group to ensure you have consistent

results. Have the lab bench sign off in your notebook that you properly can use

this skill.

Add exactly 25 mL of liquid to your graduated cylinder. Have a lab partner check

that you have appropriately added 25 mL. Have the lab bench sign off in your

notebook that you properly can use this skill.

Demonstrate the appropriate use of a volumetric pipet to your lab bench. Have

the lab bench sign off in your notebook that you properly can use this skill.

Demonstrate the appropriate use of a volumetric flask to your lab bench. Have

the lab bench sign off in your notebook that you properly can use this skill.

Determine Accuracy and Precision of Measurement Devices

Goal: Determine the accuracy (relative error) and precision (relative

average deviation) for measuring 25 mL of water using four different

tools: beaker, graduated cylinder, volumetric pipet, and volumetric flask.

A common way to calibrate volume-measuring devices is to measure the mass of

a liquid that has a well-established density. Water is commonly used since it is

readily available, and the density is well-established. Here is the basic procedure

for determining a volume using density:

1. Record the mass of a dry, empty container. Beakers or Erlenmeyer flasks work

well.

2. Measure an amount of liquid using a volume measuring device and pour the

liquid into the container of known mass from step 1. For example, measure 25

mL of water with a graduated cylinder and pour the water into a beaker.

3. Record the mass of the container holding the water.

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