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JoVE Lab Manual
Lab: Chemistry

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Lab Techniques

Lab Techniques

Learning Objectives

At the end of this lab, students should know...

Why are lab measurement techniques important?

Proper measurement techniques ensure that you accurately measure the materials that you will use in your experiments. This is essential for reproducibility.

How can you measure precise liquid volumes?

Liquid volumes should be measured with graduated or volumetric glassware, such as a volumetric flask, a graduated cylinder, or a volumetric pipette. Standard beakers and Erlenmeyer flasks should not be used for precise measurements.

What is the difference between 'to contain' and 'to deliver'?

Glassware marked ‘to contain’ will contain the specified volume of liquid when it is filled to the mark, but it may deliver slightly less than that volume. Glassware marked ‘to deliver’ will contain some extra liquid when it is filled to the mark, but it will deliver the precise volume specified.

What is measurement error?

Measurement error is the difference between the measured value and the true value. This is expressed as ‘uncertainty’, which describes the expected amount of variation between the measured and true values. Remember to write down the uncertainty of your instruments and glassware when you record your measurements.

What are significant figures?

Significant figures represent the precision of a value. All numbers other than leading or trailing zeroes are significant, including zeroes between non-zero digits. Trailing zeroes are significant only if they either follow a decimal point or are marked as significant using an overline, underline, or decimal point with no tenths place. Leading zeroes are never significant.

List of Materials

  • Sodium chloride (50 g/student)
    500 g
  • Deionized water (250 mL/student)
    2.5 L
  • Small plastic bottles with cap
  • 20-mL volumetric flask
  • 10-mL volumetric pipette
  • 10-mL pipetter
  • 50-mL beaker
  • 600-mL beaker
  • 50-mL graduated cylinder
  • 12" ruler
  • Eggs (2 eggs/student)
  • Eye dropper
  • 250-mL wash bottle
  • Stirring rod
  • Weigh boats
  • Top-loading balance
    Dependent on the lab size

Lab Prep

Source: Smaa Koraym at Johns Hopkins University, MD, USA

  1. Preparation of Laboratory

    Here we show the laboratory preparation for 10 students working individually, with some excess. Please adjust quantities as needed. 

    • To set up for this lab experiment, wear the appropriate personal protective equipment, including a lab coat, chemical splash goggles, and gloves.
    • Obtain enough small plastic bottles with caps for the number of students and label them ‘NaCl’.
    • Use a top-loading balance to weigh 50 g of NaCl directly into each bottle. Place the bottles of NaCl at the student workstations.
    • Fill enough 250-mL wash bottles with deionized water for each student to have one.
    • Set out the following glassware and equipment at each student lab station:
       1    Stirring rod
       1    20-mL volumetric flask
       1    10-mL volumetric pipette
       1    Pipetter
       1    600-mL beaker
       1    50-mL graduated cylinder
       1    12-in ruler
       1    Egg
       1    Eyedropper

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