A physical property of matter is a characteristic that can be observed and measured without changing the chemical identity of a substance. Any property that can only be observed after a chemical change occurs is a chemical property, but a physical property can be seen when no change occurs or when a physical change happens. Examples of physical changes include phase changes between states or matter and changing the form of matter by folding or cutting it.
Physical properties include traits we can observe using our senses, so they are important for describing matter.
Physical Property Examples
Physical properties include mechanical properties and any characteristic you can see, smell, taste, or touch. Here are some examples of physical properties:
- Albedo – reflectivity of an object
- Area – size of a two-dimensional surface
- Boiling point – temperature at which a liquid changes into a gas
- Brittleness – tendency to break under stress
- Color – wavelengths of light reflected by matter
- Density – amount of matter per unit of volume
- Ductility – measure of how readily a substance stretches into a wire
- Malleability – measure of how readily a substance may be pounded or pressed into sheets
- Freezing point – temperature at which a substance changes from a liquid into a solid
- Length – longest dimension of an object
- Luster – measure of the interaction between light and an object’s surface
- Mass – amount of matter in an object
- Solubility – amount of matter that dissolves in a solvent
- Temperature – measure of the thermal energy of a substance
- Viscosity – resistance to deformation by stress; resistance to flow
- Volume – three-dimensional space a substance occupies
- Weight – effect of gravity on a mass
Intensive and Extensive Physical Properties
The two broad categories of physical properties are intensive and extensive properties.
An intensive property does not depend on the size or mass of a sample. For example, density is an intensive property because it is the same no matter where you sample a substance. Other intensive properties include boiling point, freezing point, viscosity, luster, and state of matter.
In contrast, an extensive property does depend on the amount of matter in a sample. For example, mass depends on sample size. Other examples of extensive properties include length, volume, area, and thermodynamic properties such as enthalpy and entropy.
Isotropic and Anisotropic Physical Properties
Another was to classify a physical property is as isotropic or anisotropic. An anisotropic property does not depend on the orientation of the sample. For example, mass and volume are isotropic because the direction of the matter being measured doesn’t matter. An isotropic property does depend on sample orientation. For example, a crystal might appear one color when viewed from a certain angle and a different color when viewed from another angle.
Isotropic and anisotropic physical properties depend on the specimen. So, color or opacity might be an isotropic property for one substance, but not for another. Usually, these terms are reserved for optical and mechanical properties in materials science.
References
- Burgin, Mark (2016). Theory Of Knowledge: Structures And Processes. World Scientific. ISBN 9789814522694.
- Emiliani, Cesare (1987). Dictionary of the Physical Sciences: Terms, Formulas, Data. Oxford University Press. ISBN 978-0-19-503651-0.
- Meyers, Robert A. (2001). Encyclopedia of Physical Science and Technology (3rd ed.). Academic Press.