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Physical Properties
These properties record the observations and measurements of matter without changing its composition. The physical properties of any substance can be further broken down into intensive or extensive properties. Intensive properties do not depend on the amount of matter present, and include color, odor, hardness, melting/freezing point, boiling point and density. Extensive properties depend on the amount of matter present. Examples include mass, weight, volume and length.
Chemical Properties
Any substance that has a tendency to undergo a chemical reaction owing to its molecular composition is chemically reactive. The term "chemical composition" of a substance refers to the elements, electrons and chemical bonding present in the substance. This is its reactivity, which is easily seen in metals that react with acids, such as zinc reacting with hydrochloric acid to produce hydrogen gas. Iron nails exposed to air or water react with oxygen molecules to form rust. A chemical change alters the composition of the original material to form one or more different compounds. Corrosion is a common example of a chemical change involving the reaction of a metal with oxygen and water. Resistance to corrosion is a chemical property.
Density Changes
Changes in density result when a substance changes its physical state. The three states of matter are solid, liquid and gas. All matter can exist in any of these three physical states, depending on conditions. The density of most substances varies with its temperature, which in general determines its physical state. Solids are more dense than liquids, and gases are the least dense because they lose their density as they absorb heat.
Melting and Boiling Point
The melting point indicates the temperature at which a solid substance absorbs enough heat energy to change its state from a solid to a liquid. In reverse, liquid water becomes solid ice when the temperature falls to 0 degrees C., the freezing/melting point for water. Here, enough energy is removed from the liquid water so that the molecules can pack more closely together to form a solid, ice; or, as ice absorbs heat, the molecules begin to vibrate more actively and move farther apart, so that its state changes to a liquid at its melting point. Let the liquid water continue to absorb more heat and its molecules begin to vibrate more actively and pop out of the liquid, forming steam, or the gaseous phase, at the boiling point of 100 degrees C.