Characteristic Properties

A characteristic property helps you identify a substance. Out of all the elements, only copper melts at 1083 ^oC. Out of all common compounds, only H₂O has, at a specific temperature, a density of 0.98g/ml (usually rounded to 1). To say that I have 215 g of a substance in my pocket will not help you guess what it is. It may be a diamond, tangerine peels or a bunch of Kleenex. So mass is not characteristic.

Here is a list of physical properties that are characteristic:

· Density

· Melting or freezing point

· Boiling point

· Electrical conductivity, if expressed as a certain number

· Refractive index ( though I’ve never seen them use this one on provincial exams)

Here is a list of chemical properties that are characteristic for certain substances. Know all of them.

TEST	RESULT	INDICATES PRESENCE OF:
Cobalt chloride	Turns from blue to pink	Water = H2O
Glowing splint	Bursts into flames	Oxygen gas = O2
Limewater	Turns cloudy because of CaCO3	Carbon dioxide gas = CO2
Flaming splint	Popping sound and only water is left behind	Hydrogen = H2

 Properties also help distinguish groups of elements or compounds from other groups. Such a property is known as a group characteristic property. Here are some examples, many of which will be seen again later in the course, so you don't have to learn the specifics yet, but understand the general idea.

Group	Group Characteristic Properties
alkali metals	Soft, low-melting metals
acids	Conduct electricity (electrolytes) and turn blue litmus red
bases	Conduct electricity (electrolytes) and turn red litmus blue