Use of Balances and Weighing

Use of Balances and Weighing

Section 1: Understanding the Use of Balances

  • A balance is a precise instrument used to measure mass of substances required for experimental procedures.
  • Can be analytical (measuring to the nearest 0.0001 g) or top-loading (measuring to the nearest 0.01 g).
  • Accuracy and precision are key to ensure validity of scientific experiments.
  • Need to be used on a flat, stable surface, away from drafts and vibrations.

Section 2: Weighing Techniques

  • Internal Calibration: Some balances self-calibrate, but if not, use known weights to check and adjust the balance.
  • Always zero the balance before use. This guarantees accuracy.
  • Use clean, dry weighing containers to hold the substance being weighed.
  • Always handle the weighing containers with tweezers or wearing gloves to prevent contamination.
  • Do not overload the balance. It may damage the sensitive mechanism.

Section 3: Weighing Solid Substances

  • Spatulas or a scoopula are typically used for transferring solid substances to the weighing containers.
  • Add small amounts gradually. It’s easier to add more than to remove the excess.
  • Record the mass to an appropriate degree of precision.

Section 4: Weighing Liquid Substances

  • Use a pipette or graduated cylinder to measure out liquid substances.
  • Read the volume at the lowest part of the meniscus (curvature) at eye level.
  • Record the volume accurately.

Section 5: Preventing and Identifying Errors in Weighing

  • Static electricity, dust, and air currents can affect balance accuracy.
  • Keep the balance clean and free of debris.
  • Always close balance doors and wait for the reading to stabilize before recording.
  • If the reading shows an unexpected change, check for possible errors and resolve them.

Section 6: Safety and Maintenance in the Use of Balances

  • Always handle with care to avoid damaging the sensitive mechanism.
  • If damaged, report to lab supervisor immediately.
  • After use, clean gently using a brush or a cloth, ensuring no debris is left.
  • Store securely to preserve accuracy and longevity.