Mass is the preferred term to use over weight when describing properties of matter as matter can become weightless but it does not become massless.
The balance is the instrument we will use to measure mass in the middle school. The introductory assignment with the measurement of mass should involve a teacher demonstration/ explanation on the use of the balance and the introducing of the following terms: gram-beam-adjustment knob-riders-zero point.
After the introductory lesson a good homework/follow-up activity would be Lab Skill 3 from “Basic Skills in the Laboratory” by Charles E. Towne and published by Cebco Standard Publishing Company, copyright 1977.
This exercise gives the student an opportunity to practice reading the position of the riders on the beams before they begin practical application exercises.
The practical application should begin by giving students objects of known masses to help their confidence with the use of the balance. After this has been completed the massing of some common objects in metric units is also helpful.
A good way to end this section is to give the students 10 marbles and find the mass starting with a single marble and continuing with 3-5-7-9. These results then can be graphed with the number of marbles vs mass of marbles. After the graph has been constructed determine the mass of 2-4-6-8-10 marbles by interpolating the graph. Find the mass of 2-4-6-8-10 marbles on the balance and compare results. If so desired, the per cent error can be figured by actual mass of marbles minus estimated mass of marbles divided by actual mass of marble; times 100%.
(figure available in print form)
