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Question-difference between density and specific gravity


#1

Currently, I am doing a lab report for school and I have a few
questions. My teacher instructed us to find the density of an object,
such as a piece of lead, and the specific gravity. He said the
formulas were as follows: density=mass/volume (which i know is
correct) specific gravity=mass of object/displaced water of object

Now, I always thought the displaced water of the object, which I
already found, was the same as the volume of the object. Am I
correct? Because then the specific gravity would be equal to the
density, right? If you could e-mail me back ASAP, that would be
great. Thank you. Jennifer Slevin


#2
   Now, I always thought the displaced water of the object, which I
already found, was the same as the volume of the object.  Am I
correct? Because then the specific gravity would be equal to the
density, right?  If you could e-mail me back ASAP, that would be
great.  Thank you. Jennifer Slevin 

Hello Jennifer, the difference between density and specific gravity is
this:

Density is measured in units, for example kilogramms per cubic
decimeter, or other units.

Specific gravity is a mere number, applicable to any unit system,
comparing the weight of a substance of a certain volume to the weight
of the same volume of water.

If you use the metric system which is based on a kilogramm as the
mass of a cubic decimeter of water, your measurement of density of a
substance will be the same number as the specific gravity.

Many greetings, Regina


#3

Here’s my response from work done in school. In general specific
gravity refers to the mass per unit volume of liquids; density refers
to the mass per unit volume of solids. It has to do with the way the
the mass per unit volume is measured. For liquids one uses an object
of known mass and volume and insert into the liquid to see how much
volume it displaces. For solids one can take water and use its
displacement to find of water to find its mass. Eureka said
Archimedes.

Of course all the usual caveats apply, and I stand to be corrected by
my fellow Orchideans.

David


#4
Currently, I am doing a lab report for school and I have a few
questions. My teacher instructed us to find the density of an object,
such as a piece of lead, and the specific gravity.  He said the
formulas were as follows: density=mass/volume (which i know is
correct) specific gravity=mass of object/displaced water of object
Now, I always thought the displaced water of the object, which I
already found, was the same as the volume of the object.  Am I
correct? Because then the specific gravity would be equal to the
density, right?  If you could e-mail me back ASAP, that would be
great.  Thank you. Jennifer Slevin

G’day Jennifer; density is simply the same as specific gravity;
density is the name most often used by non scientists. Sorry to tell
you, but your teacher is a bit off the page! – Cheers now,

John Burgess; @John_Burgess2 of Mapua Nelson NZ


#5

Jennifer: I know you have gotten other answers through Orchid.
However, such questions always interest me because I was not a
physics/chemistry student so I generally take the opportunity to brush
up on facts I don’t have at hand. My easiest source is to always go
to Google and simply plug in my question, in this case “definition of
density” and “definition of specific gravity”. Below are 3 of the
sites where I found understandable You may enjoy looking
at these and you may find that in the future it is faster for you to
simply go to Google and research for yourself.

http://www.essex1.com/people/speer/density.html

http://www.webelements.com/webelements/properties/text/definitions/den
sity.h tml

Thanks for bringing up a topic that caused me to go look it up.
Kay