Anything that has mass and takes up space is defined as matter. The vast diversity of matter, from the air we breathe to construction metals, is distinguished by unique characteristics. A property is a trait used to describe a substance. Understanding these characteristics is foundational to chemistry and physics, allowing scientists to classify, predict the behavior of, and utilize different materials.
The Primary Distinction: Physical vs. Chemical Properties
The characteristics of matter are primarily grouped into two distinct categories based on how they are observed.
Physical properties are those that can be measured or observed without changing the substance’s fundamental chemical identity. These properties describe the substance as it currently exists. Examples include color, hardness, density, and the temperature at which a substance melts or boils. Observing the melting point of ice, for instance, only changes the physical state of the water from solid to liquid, but the chemical composition remains H₂O. (5 sentences)
Chemical properties, in contrast, describe a substance’s potential to undergo a chemical reaction and change into one or more new substances. Observing a chemical property necessarily involves a permanent change in the composition of the material. A common example is flammability, which is the ability to burn. When wood burns, it changes into ash, carbon dioxide, and water vapor, all of which are chemically different from the original wood. The capacity of iron to rust is another chemical property, as the iron metal transforms into iron oxide when exposed to oxygen and water. (5 sentences)
Physical Properties Defined by Scale: Intensive and Extensive
Within the category of physical properties, further classification exists based on how the characteristic relates to the sample size.
Intensive properties are characteristics that do not depend on the amount of matter present in a sample. Whether one examines a thimbleful or a barrel of pure water, the boiling point will remain 100 degrees Celsius at standard atmospheric pressure. Other intensive properties include color, temperature, hardness, and electrical conductivity. Intensive properties are particularly useful for identifying an unknown substance. (4 sentences)
Extensive properties, however, are characteristics that are directly proportional to the amount of matter in the sample. These properties change whenever the quantity of the substance changes. Common examples of extensive properties include mass, volume, and total energy. These measurements are important for quantitative analysis, but they cannot be used alone to identify a substance. (4 sentences)
The relationship between intensive and extensive properties yields some of the most useful measurements in science. Density is a prime example, calculated by dividing the extensive property of mass by the extensive property of volume. The resulting value for density is an intensive property. (3 sentences)
Understanding Chemical Properties: The Nature of Transformation
Chemical properties indicate the potential for a substance to undergo a change in composition under specific conditions.
Reactivity describes how readily a substance will combine chemically with other substances. For instance, fluorine is an extremely reactive element, capable of causing substances like glass to burn. (2 sentences)
Flammability describes a material’s ability to ignite and sustain combustion. Understanding the flammability of materials like gasoline dictates handling and storage protocols. (2 sentences)
Corrosion refers to the deterioration of a material due to a reaction with its environment. The formation of rust on iron is a case of corrosion. Chemical stability, conversely, describes a substance’s resistance to chemical change or decomposition. The study of these transformation-based properties allows scientists and engineers to predict material behavior and determine the best application for any given substance. (4 sentences)