Measurement forms the bedrock of chemistry, where accuracy depends on precise values. In the laboratory, “tare” is a frequently used term related to obtaining this precision. Taring a balance is a technique that re-establishes the zero point of a digital balance after a container has been placed on the weighing pan. This action allows the instrument to ignore the weight of the vessel and focus solely on the mass of the substance being measured, ensuring chemical calculations are based on the true quantity of the material.
Defining Tare and Its Purpose
Chemical samples, whether solid or liquid, cannot be placed directly onto a balance pan. They must be held in a container, such as a beaker, a watch glass, or a weigh boat. If the container’s mass were not accounted for, the resulting measurement would be inflated and inaccurate. The purpose of the tare function is to electronically remove this known, unwanted mass from the measurement.
By taring the balance, the display is reset to zero grams, even though the container is physically sitting on the pan. This programs the balance to subtract the container’s mass from any subsequent total mass measurement. Isolating the mass of the pure sample, or analyte, from the mass of its vessel is mandatory for reliable experimental outcomes, particularly when using analytical balances that measure to the nearest 0.0001 g.
The Mechanics of Taring in the Lab
The practical application of taring is a straightforward procedure performed on a digital laboratory balance. Before weighing, the balance must be prepared by ensuring it is level, clean, and stabilized. The first step is to place the empty, clean, and dry weighing vessel centrally on the balance pan.
Once the container is stable, the operator presses the button labeled “Tare” or “Zero.” The balance registers the container’s weight and electronically adjusts the display to read 0.000 g. Taring is the specific act of zeroing out a non-zero mass, distinct from zeroing an empty balance before use.
After the display confirms the zero reading, the sample material is carefully added to the tared container. Since the container’s weight has been canceled out, the displayed value represents the mass of the sample alone. This immediate readout eliminates the need for manual subtraction and reduces the chance of calculation errors.
Gross Mass vs. Net Mass
Taring utilizes the relationship between three distinct mass terms to provide a direct measurement. The “tare mass” is the weight of the empty container placed on the balance pan, which the balance subtracts from the total reading.
The “net mass” is the weight of the sample itself, which is the final value the chemist seeks. This is the mass displayed after the sample has been added to the tared container. Conversely, the “gross mass” is the total combined weight of both the container and the sample together.
Using the tare function allows the balance to perform the mathematical operation: Gross Mass minus Tare Mass equals Net Mass. This immediate isolation of the net mass makes taring the standard method for quantitative chemical measurements.