Tools Used to Measure Masses of Liquids

• Chemists use a variety of tools and instruments to aid them in weighing liquids. Robert Houser/Photodisc/Getty Images

  When you purchase a container of liquid, the label affixed to the bottle always provides the amount of liquid inside in terms of its volume, be it in milliliters, quarts, gallons or any other volume units. Within the chemistry lab, however, liquids' masses can also be important, particularly when it comes to calculations. Academic and professional chemists the world over use several tools to aid them in measuring the masses of liquids.

Measuring Tools

• For a chemist, the volume of a certain liquid is just as important as its mass. For example, if a chemist pours a random amount of water into a beaker and then weighs it, she has no other data against which to compare the weight. As such, chemists measure out specific volumes of liquid reagents prior to weighing them. The most common tool for this purpose is called a graduated cylinder, a long, narrow tube with volume measurements along its entire height, and with a special tip to reduce errors that result in liquid being lost from pouring.

Weighing Containers

• As liquids take the shape of whichever container they're in--and lose shape entirely if they're without a container--it's essential to record their mass when they're inside something. Which glassware a chemist will use for a liquid will depend upon what he has available on a given day, the amount of liquid and a number of other factors, but will most commonly entail a beaker, a wide, short cylinder, or an Erlenmeyer flask, which starts out like a beaker at the bottom, but gradually comes together to a more narrow opening, resulting in sloped walls and a cone shape.

Balances

• Although they have evolved since the days when they had two separate weighing boats, balances--which are mostly all electronic now--are essential to recording masses of liquids. One important feature balances possess is the "Tare" button. In order to accurately weigh a liquid, the chemist needs to ensure the mass of the beaker or Erlenmeyer flask won't be taken into account. If she wanted to, she could weigh the container, record its mass and subtract that from the final mass of the liquid and the container. Electronic balances, however, take care of that for her. By placing an empty piece of glassware onto the balance and pressing "Tare," she ensures whatever mass the container possesses won't be included in the mass of the liquid, as evidenced by the fact the balance reads negative when she removes the beaker or flask.