Study of Matter Compounds  Elmhurst College
Atoms Physical Properties Mixtures  Chemistry Department
Elements Chemical Properties    Virtual ChemBook

What are Physical Properties and Changes?

Physical Properties:

Physical properties can be observed or measured without changing the composition of matter. Physical properties are used to observe and describe matter.

Physical properties include: appearance, texture, color, odor, melting point, boiling point, density, solubility, polarity, and many others.

The three states of matter are: solid, liquid, and gas. The melting point and boiling point are related to changes of the state of matter. All matter may exist in any of three physical states of matter.

In the graphic on the left the solid and liquid forms of water - ice are shown.

 Physical Changes:

A physical change takes place without any changes in molecular composition. The same element or compound is present before and after the change. The same molecule is present through out the changes. Physical changes are related to physical properties since some measurements require that changes be made.

Melting Point: As solid matter is heated it eventually melts or changes into a liquid state at the melting point.
Ice (a solid form of water) melts at 0 oC and changes to the liquid state.

Carbon dioxide melts at -56.6oC

Boiling Point: As the liquid matter is heated further it eventually boils or vaporizes into a gas at the boiling point.
Liquid water boils and changes into a gas, usually called steam or water vapor at 100 oC. In all three states the same molecules of water (H2O) are present.

Carbon dioxide boils at -78.5oC

In the graphic on the left a block of dry ice as a solid is changing to the gaseous state. The molecules of CO2 are present throughout.

Sublimation:

Iodine has a relatively unique property in that it can change directly from a solid to a gaseous state without going through the liquid state. As the iodine is heated it undergoes a physical change to the gas state as shown in the graphic on the left. Iodine in the gas state is a beautiful violet color.