PHYSICAL AND CHEMICAL CHANGES OF MATTER

The properties of a substance are those characteristics that are used to identify or describe it.  When we say that water is "wet", or that silver is "shiny", we are describing materials in terms of their properties.  Properties can be divided into the categories of physical properties and chemical properties. 

Physical properties are readily observable, like; color, size, luster, or smell.  

Chemical properties are only observable during a chemical reaction.  For example, you might not know if sulfur is combustible unless you tried to burn it.

Physical changes are those changes that do not result in the production of a new substance.  If you melt a block of ice, you still have H₂O at the end of the change.  If you break a bottle, you still have glass.  Painting a piece of wood will not make it stop being wood.  Some common examples of physical changes are; melting, freezing, condensing, breaking, crushing, cutting, and bending.  Special types of physical changes where any object changes state, such as when water freezes or evaporates, are sometimes called change of state operations.

Chemical changes, or chemical reactions, are changes that result in the production of another substance.  When you burn a log in a fireplace, you are carrying out a chemical reaction that releases carbon.  When you light your Bunsen burner in lab, you are carrying out a chemical reaction that produces water and carbon dioxide.  Common examples of chemical changes that you may be somewhat familiar with are; digestion, respiration, photosynthesis, burning, and decomposition.

By: Science Help Online Chemistry

Your questions, notes, drawings: