Measurement of Weight

Weight Definitions

Weight: force of gravity on an object. Balances: instruments used to measure weight. Mass: amount of matter in an object.

Expressed in grams (g) Beam: also known as the lever of a balance that holds the weighing pans.

When the bean is balanced that means gravity has the same measurement on each side.

Taxonomy of Balances

Range & Capacity: the weight span of how much a balance can weigh from heaviest to lightest.

Capacity: the maximum weight a balance can sustain.

Sensitivity & Readability: the smallest weight that will cause a shift in the weight reading.

Readability: the smallest amount of weight a balance can read.

Types of Balances

Analytical Balances: highly sensitive and can weigh samples to the nearest tenth of a milligram (0.0001g).

Microbalances: can weigh samples to the nearest microgram (0.000001g).

Ultramicrobalances: can weigh samples to the nearest tenth of a microgram (0.0000001).

Mechanical balances: balance containing a beam and balance pans. Must have a reliable known to measure the unknown as accurately as possible.

Electronic balances: uses an electromagnetic force rather than known weights to counter balance the sample. Produces an electronic signal.

Proper Use of a Balance

Always make sure you are using the proper balance. Check to make sure the balance is clean. Make sure the balance is on, level and is reading all zeros. If available use calibration weights to confirm the balance will properly

measure the sample. Tare the weight of the container or “boat” used to collect the sample. Place the sample on the weight pan, carefully so that it does not spill over

onto the balance. Once the sample is properly weighed remove the container or “boat” and

clean the balance and the area around it. Turn off the balance if it is not being used.

Helpful Web Links

Different Balances and Techniques

Calibrating an Analytical Balance

Using an Analytical Balance

Using a Table Top Laboratory Balance

Measurement Lab

After watching the videos, the next thing you need to do is practice weighing by doing the Measurement Lab. As always, practice makes perfect!