PHYSICAL PROPERTIES OF MATTER
A physical property is any measurable property the value of which describes a physical system's state. The changes in the physical properties of a system can be used to describe its transformations (or evolutions between its momentary states).
An object or substance can be measured or perceived without changing its identity. Physicalproperties can be intensive or extensive. An intensive property does not depend on the size or amount of matter in the object, while an extensive property does. In addition to extensiveness, properties can also be either isotropic if their values do not depend on the direction of observation or anisotropic otherwise. Physical properties are referred to as observables. They are not modal properties.Often, it is difficult to determine whether a given property is physical or not. Color, for example, can be "seen"; however, what we perceive as color is really an interpretation of the reflective properties of a surface. In this sense, many ostensibly physical properties are termed as supervenient. A supervenient property is one which is actual (for dependence on the reflective properties of asurface is not simply imagined), but is secondary to some underlying reality. This is similar to the way in which objects are supervenient on atomic structure. A "cup" might have the physical properties of mass, shape, color, temperature, etc., but these properties are supervenient on the underlying atomic structure, which may in turn be supervenient on an underlying quantum structure.
Physicalproperties are contrasted with chemical properties which determine the way a material behaves in a chemical reaction.
Physical change is a concept introduced to contrast with the concept of chemical change. A physical change is any change not involving a change in the substance's chemical identity. Matter undergoes chemical change when the composition of the substances changes:one or more substances combine or break up (as in a relationship) to form new substances. Physical changes occur when objects undergo a change that does not change their chemical nature. A physical change involves a change in physical properties. Physical properties can be observed without changing the composition of matter. Examples of physical properties include: texture, shape, size, color,volume, mass, weight, and density.
An example of a physical change occurs when making a baseball bat. Wood is carefully crafted into a shape which will allow a batter to best apply force on the ball. Even though the wood has changed shape and therefore physical properties, the chemical nature of the wood has not been altered. The bat and the original piece of wood are still the same chemicalsubstance.
Changes are sometimes hard to categorize strictly as physical or as chemical. Dissolving a salt in water involves the breaking of chemical bonds, yet is often described as a physical change. Some teachers hold that a chemical change is a rearrangement of atoms, but many physical changes also involve the rearrangement of atoms. Many chemical changes are irreversible, and many physical changesare reversible, but reversibility is not a certain criterion for classification. Although chemical changes are often recognized by an indication such as odor, color change, production of a precipitate, or production of a gas, every one of these indicators can result from physical change.
In a chemical change, bonds are broken and formed between different atoms. This breaking and forming of bondstakes place when particles of the original materials collide with one another. Some exothermic reactions may be hot enough to cause certain chemicals to also undergo a change in state; for example in the case of aqueous solutions, bubbles may not necessarily be newly produced gas but instead water vapor.
When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an...