Chemistry · Some Basic Concepts Of Chemistry · NEET
A reference standard is one fixed value of a unit that scientists all over the world agree to use. For example, the kilogram was defined (since 1889) using a platinum-iridium (Pt-Ir) cylinder kept in a sealed jar at the International Bureau of Weights and Measures in France. Every balance is finally traced back to this one master value, so measurements match everywhere.
Calibration means checking a measuring device against a known standard and adjusting it so it reads correctly. When a company makes a metre stick or an analytical balance, they compare it to the reference standard. This makes sure your reading of 1 kg really means 1 kg.
The reference standard is the fixed master value (the 'original'). Calibration is the process of comparing your instrument to that standard. Standard = the thing you trust; calibration = the act of matching to it. One is an object/value, the other is an action.
Over time and use, devices can drift and give slightly wrong readings. Calibration against a reference standard keeps them accurate and reliable. Without it, two people measuring the same object could get different answers, which is dangerous in chemistry, medicine, and industry.
Each industrialised country, including India, has a National Metrology Institute (NMI) that maintains national standards of measurement. In India this work is done by the National Physical Laboratory (NPL). These bodies follow the metre treaty (signed in 1875), and update unit definitions when better methods improve accuracy.
Yes. A Celsius thermometer is calibrated from 0 degrees to 100 degrees using two fixed reference points: the freezing point of water (0 degrees) and the boiling point of water (100 degrees). These fixed points act like reference standards for temperature.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
A platinum-iridium (Pt-Ir) cylinder, stored in an airtight jar at the International Bureau of Weights and Measures in France since 1889.
India's National Metrology Institute, the National Physical Laboratory (NPL), maintains and traces national standards of measurement.
The metre treaty was signed in 1875. Member nations agree to update unit definitions whenever accuracy improves.
Yes. Definitions of units keep changing with time. When a more accurate method is found, member nations agree to adopt the new definition, as happened with the kilogram.
You do not do calculations here, but you must know the definitions: reference standard = fixed master value; calibration = comparing instruments to it. NEET asks these as short factual or trap questions.
