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Measuring mass

What do we use triple beam balances for?

To measure masses very precisely. The reading error is only 0.05 gram  ( 5/100th of a gram)


With the pan empty, move the 3 sliders to their leftmost positions, so that the balance reads zero.

If the indicator on the far right doesn’t point to the fixed mark, then calibrate the balance by turning the set screw on the left under the pan.

Once the balance has been calibrated, place the object to be measured on the pan.

Move the 100 gram slider along the beam to the right until the indicator drops below the fixed mark.

The notch to the left of this point indicates the number of hundreds of grams.
Now move the 10 gram slider along the beam to the right until the indicator drops below the fixed mark.

The notch to the left of this point indicates the number of tens of grams.

The beam in front is not notched; the slider can move anywhere along the beam.

The bold numbers on this beam are one-grams.

The tick marks between the bold numbers indicate tenths  ( 1/10) of grams.
To find the mass of the object on the pan, simple add the numbers from the three beams.

As with a ruler, it is possible to read the front scale to the nearest half tick mark.

Here is how to read the beams:

Learning Standards

Massachusetts Science and Technology/Engineering Curriculum Framework

Building on : Skills of Inquiry, Experimentation, and Design:
• Select and use appropriate tools and technology (e.g., calculators, computers, balances, scales, meter sticks, graduated cylinders) in order to extend observations.
• Keep accurate records while conducting simple investigations or experiments.
• Conduct multiple trials to test a prediction. Compare the result of an investigation or experiment with the prediction.

America’s Lab Report:  Investigations in High School Science (2005)
National Research Council of the National Academies, the National Academies Press

Laboratory Experiences and Student Learning:

Developing practical skills. In laboratory experiences, students may learn to use the tools and conventions of science. For example, they may develop skills in using scientific equipment correctly and safely, making observations, taking measurements, and carrying out well-defined scientific procedures.Understanding of the nature of science. Laboratory experiences may help students to understand the values and assumptions inherent in the development and interpretation of scientific knowledge, such as the idea that science is a human endeavor that seeks to understand the material world and that scientific theories, models, and explanations change over time on the basis of new evidence.
Cultivating interest in science and interest in learning science. As a result of laboratory experiences that make science “come alive,” students may become interested in learning more about science and see it as relevant to everyday life.
Developing teamwork abilities. Laboratory experiences may also promote a student’s ability to collaborate effectively with others in carrying out complex tasks, to share the work of the task, to assume different roles at different times, and to contribute and respond to ideas.

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