Minerals - Station 8     Characteristic properties:  Density
Wednesday, May 09, 2012
8:39 AM
Station 8 :  Density 
An important characteristic 
Density definition
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Click on the image for the density interactive.
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Did you know - definition of gram
Density is an important property of all materials, not just minerals.  Dense materials weigh more for a given size relative to other materials.  A cubic centimeter of water happens to weigh 1 gram.   A typical mineral will have a density three times greater than water.  The weight in a mineral comes from the weight and arrangement of atoms within minerals.   The heavier the atoms inside the mineral, and the more closely packed the atoms, the denser the mineral.   
One of the reasons that density is important.  The density of a material will determine whether that solid sinks or floats in a liquid
Another reason, density can be used to distinguish minerals.  Fool's gold won't have the same density as real gold..
Hold each of the following cubes in your hand.   Since they are all the same three-dimensional size, the weight difference you sense reflects a density difference.  Put them in the order of increasing density, 1 being the lightest.
 Heaviest
Material
1
2
3
4
5
 Weight and density are NOT the same thing.
The acrylic cube is light for its size.  
The copper cube is heavy for its size.
But whatever the copper cube weighs, if you just had a bigger piece of acrylic, it would weigh the same as the smaller copper cube.
So weight depends on the size of the material you have and any material can be any weight depending on its size.
But when you hole the same-sized cubes in your hand, there is something about acrylic that is lighter than the copper.   It's easiest to detect this when the objects are the same size so you are not misled by the weight.  That characteristic of lightness or heaviness of the material for its size is called density. 
Things are dense when the invisibly small atoms inside that material are packed closer together, or the atoms in side that material are relatively heavy themselves, like atoms of gold.
You'll learn more about density in future science classes.  
For now, remember that density and weight are related, but NOT the same thing.
Density doesn't depend on size, while weight does.
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