Properties of matter can be divided in two ways: extensive/intensive and physical/chemical. An extensive property depends on the amount of matter that is being measured. These include mass and volume (Figure 1). An intensive property does not depend on the amount of matter. These include density and color. Both extensive and intensive properties are physical properties, which can be measured without changing the substance's chemical identity. The freezing point of a substance is a physical property. When water freezes, it's still water (Figure 2). States of matter are the distinct forms that different phases of matter take on.
A chemical property, meanwhile, is any of a material's properties that becomes evident during a chemical reaction; that is, any quality that can be established only by changing a substance's chemical identity. Simply speaking, chemical properties cannot be determined just by viewing or touching the substance; the substance's internal structure must be affected for its chemical properties to be investigated.
Mass is a measure of an object's inertia. It is proportional to weight: the more mass an object has, the more weight it has. However, mass is not the same as weight. Weight is a force created by the action of gravity on a substance, while mass is a measure of an object's resistance to change in motion.
Mass is measured by comparing the substance of interest to a standard kilogram, called the International Prototype Kilogram (IPK). The IPK is a metal cylinder where the height and diameter both equal 39.17 millimeters. It is made of an alloy of 90% platinum and 10% iridium. Thus, the standard kilogram is defined and all other masses are a comparison to this kilogram.
Volume is a measure of the amount of space occupied by an object. Volume can be measured directly with equipment designed using graduation marks, or indirectly using length measurements depending on the state (gas, liquid, or solid) of the material. A graduated cylinder, for example, is a tube for holding liquids that is marked and labeled at regular intervals, usually every 1 or 10 mL. Once a liquid is placed in the cylinder, one can read the graduation marks and record the volume measurement. Solid objects that have regular shape can have their volume calculated by measuring their dimensions. In the case of a box, its volume is equal to its length times width times height.
Another quantity of matter is the amount of substance. This can either represent a counted quantity of objects (e.g., three mice or a dozen bagels), or the indirectly determined number of particles of a substance being dealt with, such as how many atoms are contained in a sample of a pure substance. In chemistry, the latter quantity is described in terms of moles. One mole is defined as the number of particles in 12 grams of the isotope Carbon-12. This number is 6.02214078 x 1023 particles.
Keeping in mind that the chemical structure of the compound undergoing analysis must change for a property to be called chemical, here are several examples of chemical properties:
- Heat of combustion - the energy released when a compound undergoes complete combustion (burning) with oxygen (symbol is ΔHc).
- Chemical stability - many compounds are reactive with water or air, undergoing reactions such as oxidation or hydrolysis, which are chemical changes.
- Flammability - whether a compound will burn when exposed to flame. Again, burning is a chemical reaction, commonly a high temperature reaction with oxygen in the air.
- Preferred oxidation state - many metals have a lowest-energy oxidation state that they will react to achieve if another element is present to accept or donate electrons.