Physical Properties


Definition - What does Physical Properties mean?

Physical properties are those general properties you notice most readily about a substance, such as its size, state of matter (solid, liquid, or gas), color, mass, density and strength. Values for physical properties can be determined by tests that don't alter the substance being tested. Tests such as determining the color or size of an object don't change it in any way.

Physical properties are the characteristics of matter that can be observed and measured without any change to the chemical identity of the sample. A physical property measurement might change the arrangement of matter in a sample but not the structure of its molecules. When a chemical change or reaction occurs, then the characteristics observed are deemed to be chemical properties.

Physical properties are measurable, with values describing the state of a physical system. Changes in the physical properties of a system can be used to refer to its changes between momentary states.

A material's physical properties are often studied in the field of materials science, and are a key factor in the material selection process when choosing appropriate materials that can resist or prevent corrosion.

Physical properties are oftentimes referred to as observables. A quantifiable physical property is known as a physical quantity.

Corrosionpedia explains Physical Properties

Physical properties are studied alongside chemical properties in order to determine the way in which a material behaves in a chemical reaction.

A given element may have different physical properties in different phases or in different compounds.

Classifications for Physical Properties

There are two classes of physical properties:

  1. An extensive property depends on the sample's size. Examples of extensive properties are variables such as shape, volume and mass.
  2. An intensive property, on the other hand, is one that does not depend on the size or amount of matter in a sample. It is a constant characteristic of the material regardless of how much matter is present. Examples of intensive properties are the melting point and density.

These classifications are usually only valid in those cases where a smaller subdivisions of the sample does not interact when combined in some physical or chemical process.

Physical properties are also classified with respect to the directionality of their nature. For example, isotropic properties do not change with the direction of observation, while anisotropic properties have spatial variance.

Supervenient Properties

It can be difficult to determine if a given property is a physical property or not. Color, for instance, can be seen and measured; however, color itself is really an interpretation of the reflective properties seen in a surface and the light that is used to illuminate it. For this reason, many ostensibly physical properties are called supervenient.

A supervenient property refers to one that is actual but is secondary to some underlying reality. This is like the way in which objects are adscititious on the atomic structure. For instance, a pencil may have the physical properties of mass, shape, color, temperature and so forth, but these properties are supervenient on the underlying atomic structure, which may in turn be supervenient on an underlying quantum structure.

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