How To Measure Mass Using a Balance

How To Use a Scale or Balance

Genetic Engineer weighing chemicals
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Mass measurements in chemistry and other sciences are performed using a balance. There are different types of scales and balances, but two methods can be used on most instruments to measure mass: subtraction and taring.

Proper Use of a Balance

  • Be sure you understand how to use a balance before taking mass measurements.
  • The balance should be clean and free of debris.
  • The balance should be on a level surface.
  • Never place a sample directly on the balance. You should use a weighted boat, weighing sheet, or another container to hold the sample. Some chemicals you may use in a lab could corrode or otherwise damage the surface of the weighing pan.
  • If the balance has doors, be certain to close them before taking a measurement. Air movement impacts the accuracy of mass measurements. If the balance does not have doors, make certain the area if free of drafts and vibrations before measuring mass.

Mass by Difference or Subtraction

mass of sample = mass of sample/container - mass of container

  1. Zero the scale or press the tare button. The balance should read "0".
  2. Measure the mass of the sample and container.
  3. Dispense the sample into your solution.
  4. Measure the mass of the container. Record the measurement using the correct number of significant figures. How many this is will depend on the particular instrument.
  5. If you repeat the process and use the same container, do not assume its mass is the same! This is particularly important when you are measuring small masses or are working in a humid environment or with a hygroscopic sample.

Mass by Taring

  1. Zero the scale or press the tare button. The scale reading should be "0".
  2. Place the weighing boat or dish on the scale. There is no need to record this value.
  3. Press the "tare" button on the scale. The balance reading should be "0".
  4. Add the sample to the container. The value given is the mass of your sample. Record it using the proper number of significant figures.

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