Standard status is a reference point for materials used in research and communication. The standard state is the natural condition of a material, often at 1 atm or 1 M concentration. Researchers can make assumptions about standard states, but they can fluctuate. The superscript symbol ° indicates a material is in its standard state. Property tables use the standard state as a reference for describing activities under different conditions. It is important to provide information about the state of materials during experiments.
Standard status is an arbitrary condition set for a material in order to create a standardized reference point. This lets researchers and others who want to communicate information about the substances they work with know that people reading that information will understand the benchmark used to measure change, activity, and other characteristics. Some organizations have established guidelines for establishing standard status for various items and expect their members to abide by them.
Classically, the standard state of a material is its natural condition when it is at one atmosphere of pressure or at a concentration of 1 mole per litre. While this is not dependent on temperature, some researchers may note 77°F (25°C) as the standard temperature in this state for reference, as it could be important when discussing chemical activity. With this as a point of reference, a researcher can more easily describe what happens when pressure and other environmental characteristics change.
Researchers can make hypotheses about the standard state of the elements; they are assumed to be pure, for example, unless the documentation states otherwise. Those assumptions are also standardized to ensure that researchers are working with the same background information. If confusion is likely, a researcher can specify what is meant by a standard state in a given experiment or discussion. Despite the “standard” in the name, standard states can actually fluctuate, and researchers can tailor them to meet their needs.
Property tables of various materials use the standard state as a reference when describing their activities at higher and lower temperatures, pressures, and other conditions. This is the zero line that a researcher can use to measure degrees of change. For the purposes of introductory science courses, teachers and textbooks often define standard states in a simplistic way to give students the basic information they need without overloading them. As students progress in chemistry, they may encounter more advanced discussions of standard states.
The superscript symbol ° can be used to indicate that a material is in its standard state. In the experimental documentation, it is important to provide information about the state of the materials at the time of the experiment. This will make it easier to test and repeat the results. In essence, the standard state is the “normal” for the material under discussion. If the material were in a different state, it would need to be annotated to put the results into context.
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