1Most state variables cannot be measured absolutely. One can only determine their relative values. V/Vref, T, P, H, U, S, etc. Examples:L = (L/Lref)Lref=> calculate VT = T + TrefS = S + SrefTo determine the values of T, P, H, etc., we need to know a reference value or a standard. As a result, Standard States1. Weight and height.Reference Values of Physical QuantititiesThe standard kilogramhoused at the International Bureau of Weights and Standards near Paris. 90% platinum and 10% iridium. US National meter#27, a copy of international metermade of platinum and iridium in France. It is housed at the National Institute of Standard and Technology Museum. 2. Pressure- Room pressure: in the clinic- Vacuum pressure: in thermodynamics3. Temperature-Temperature of triple point of water at P = 1 atm(for 0C)-Temperature of gases as V 0 at any P (for K)
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