Characteristics used to tell the difference between matter
A physical property is a characteristic of a substance or object that does not involve a chemical change, such as density, color, or hardness. It can be observed without changing the identity of the substance or object.
Using Chalk as an example: If it is a whole piece it is still chalk. Now break it into three pieces and it is still chalk. Now crush it and it is still chalk. So I guess the answer is: Material that doesn't change what it is even when broken down.
A physical property is a characteristic you can observe or measure without changing the composition. 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. Physical properties 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 a surface 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.
The cheap way to define a physical property is to note that it is not a chemical property (so if you know what that is, you are on your way) and it is certainly not a nuclear property.
For example, a mixture is a physical property.
Nuclear properties aside, some things which look very chemical are pushed into the physical realm. For example, things that look like molecules but do not have a definite chemical formula (long strings of matter of indifferent number of atoms) are considered physical.
So temperature, size, shape, sharpness, color and the like are considered physical properties.
Physical properties are those that can be seen or measured, such as color, shape, size, opacity, conductivity, hardness, density, texture, boiling point, and melting point.
These are opposed to chemical properties, which define how a substance reacts with other substances.
