Teaching About the Triple Beam Balance

Students in middle school and high school often work with a triple beam balance when doing laboratory experiments, but there are several ways a teacher might improve the use of the triple beam balance.

The teacher will often demonstrate the way to safely move the triple beam balance from one location to another. Typically one hand is placed under the balance while another holds the heavier side of the balance. The goal is to hold the balance in a way that will not hurt the scale. The teacher will point out that all of the sliding units must at first be moved to the left and must drop into a notch and then the scale is balanced to read "0" with no weight on the scale. In most cases a piece of paper about 1/3 the size of the top of the scale is then placed on the scale and the scale is again balanced to "0". When powders are going to be measured they are placed on the paper, but because the scale has been balanced with the paper then a true reading of the weight in grams is then possible to be measured. The extra weight causes the scale to be unbalanced and then the sliders are moved to re-balance the scale. This is where most students have difficulty. Many students will not move the sliders into the drop groves for the heavier sliders. One slider does not drop into a grove.

Triple Beam Balances have a limit to the amount of grams that they can weigh. The different models have different limits and in some cases other sliders can be added. In the graphic there are larger examples of the three sliding sections. If these sections are made into a transparency they can be placed on an overhead projector. The three sample sliders can be cut out from the transparency and they can be moved on the transparency to represent different weights. Remember two of the sliders must be positioned into a groove, but one can be moved anywhere on the slide beam (the one that goes to 10 grams).

Students will need to learn to place liquids into a beaker and measure the weight, but they will have to learn to subtract the weight of the beaker to get the weight of the liquid. The teacher can pre-measure dozens of objects which the students can practice with the measurement process. If each practice item is labeled: "Item A"; "Item B" etc. then later the teacher can check to see if the students have calculated a proper weight.

NOTE: An additional graphic has been added recently which is the basically blank worksheet that I would use. I would paste in pictures of the items I wanted students to measure and place identical items at each laboratory station.

Students should not weigh any food items and should be told not to do this in the laboratory. The top of the Triple Beam Balance may have residue from past experiments and some of those residues could be dangerous. NOTE: Scales that are at home and used to measure food, should not be used to measure chemicals either. There are many safety procedures that should be covered before students do laboratory experiments so in general they should not be using any laboratory equipment without receiving the safety lectures first.

Also, students often have confusion about mass and weight. They also may be confused on the related topics of volume and density. The use of the Triple Beam Balance can help in clearing up misunderstanding.