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Specific Properties of Matter
Name: Erin
Status: student
Grade: 9-12
Location: NJ
Country: USA
Question:
What exactly is "specific" property of matter? Would
density be considered one because it is not always constant?
Replies:
A 'specific' property is a property that depends on or is calculated based
on another measurable property. You give an example of density; density is
considered 'specific' because it can be calculated from volume and mass.
Some other good examples are:
- specific gravity - the density of a material relative to the density of
water (volume and mass of the object, known density of water)
- specific heat - the amount of energy required to raise a specific mass by
a specified number of degrees of temperature (temperature, heat input, mass)
- 'g-force'- acceleration relative to earth's gravity (acceleration, known
acceleration due to gravity on earth) -- and thanks to Wikipedia for
reminding of that one!
Often, specific properties are a ratio of two measurements with identical
units. Specific gravity, for example, is a ratio of one density to another.
When performing calculations, specific units are easier because they are
'dimensionless' (they do not have units). It's also easier to think about
certain properties relative to a commonly known property. Like how dense
something is in terms of water instead of having to figure out of 60 pounds
per cubic foot is going to float or not...
Hope this helps!
Burr Zimmerman
Erin,
If I understand your question correctly, you are looking for properties that
all matter have. The first thing that comes to mind is "mass". Since mass is
a measure of the amount of matter, then this is something that all matter
have.
Greg (Roberto Gregorius)
I have never seen a precise definition of a "specific" property. The
only properties I can think of that are called "specific" are specific
heat and specific gravity. Both of these are intrinsic quantities, that
is, they are a property of the material itself, and do not depend on how
much material is present.
For example, density, which is the mass of a sample of a substance
divided by its volume, is an intrinsic property. No matter how much of
the stuff you have, changing the amount does not automatically change
the density. By contrast, mass is an extrinsic property. Doubling the
amount of stuff doubles the mass.
Although density is not necessarily constant, it does not depend in
particular on how mu7ch stuff you have. Rather, it depends on pressure,
temperature, and crystalline form (for solids). Increasing the amount
of stuff does not necessarily change the density; sure, if you cram
twice the amount of stuff into the same volume, you are increasing the
density, but in doing so you need to change the some other quantity as
well.
I do not know if this is general, but the two "specific" properties
mentioned above are actually pure, unitless ratios as well as being
intrinsic. "Specific gravity" is the density of a substance divided by
the density of water. By the same token, "specific heat" is the
intrinsic heat capacity of a substance divided by the intrinsic heat
capacity of water.
Richard Barrans, Ph.D., M.Ed.
Department of Physics and Astronomy
The term "specific" does not have a well defined chemical meaning. There are
terms like "specific" gravity, and "specific" heat. A common meaning (but by
no means "cast in stone") is that the term "specific" (whatever) refers to
the value of some property per gram of material.
Vince Calder
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Update: June 2012
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