DENSITY

It is a measure of compactness of how much mass is tightly squeezed into a given volume.

Is the ratio of mass and volume in an object.

D= M/Vg/ml or g/cm3

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D = m/v (g/cm3) (g/ml) Mass usually expressed in grams Volume usually expressed in cm3 or

milliliters, etc.

Density = amount of matter per unit volume Density is the ratio of mass to volumeIf the volume stays the same and the mass

increases . . . the density will increaseIf the mass stays the same and the volume

increases . . . The density will decrease

The “DMV” Triangle forVolume, Mass, and Density

M ÷ ÷D X V

Density = MV

Volume = MD

Mass = D x V

How close the atoms or molecules are to each other

More than “heaviness” - density includes how much space an object takes up!!

All substances have density including liquids, solids, and gases

Density is the measure of the “compactness” of a material

What would take up more space??? A kilogram of feathers…..or a kilogram of steel??

OR

“Compactness”

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The density of water is 1.0 g/ml

Objects with densities greater than 1.0 g/ml will sink in water

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Objects with densities less than 1.0 g/ml will float on water

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Ice floats therefore it is less dense than water

Ice mostly remains underwater with only a portion of it being exposed

Solids

Ice vs. water…..

GasesHow much kinetic energy do the molecules have??

The greater the kinetic energy ……the greater the volume …… and the less dense that gas is!!

Therefore, cold air is more dense than warm air

Low pressure weather system means warmer air tends to rise,

High pressure systems indicate a colder more dense air mass that will……. SINK!!!

LIQUIDS The more dissolved solids in a solution, the more

dense (such as ocean water)

Cold water in lakes tend to sink (this creates a constant mixing of water, nutrients, and other substances)

Kinetic energy again!!

Denser layers to less dense layers…..

What would happen???? Mercury density = 13600kg/m3

Lead density = 11340kg/m3

Lead floats on liquid mercury!

Solids

Ice vs. water…..

SOLIDS

Ice is less dense than water (which is why lakes and ponds have a thin layer of ice covering in winter, with water underneath)

Various rocks, woods, metals have a characteristic density specific to that substance

Wouldn’t you like to have a bunch of THIS dense material?

Archimedes and the Kings Crown

http://3quarksdaily.blogs.com/3quarksdaily/images/2007/07/18/archimedes.jpg

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If 96.5 grams of gold has a volume of 5 cubic centimeters, what is the density of gold?

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If 96.5 g of aluminum has a volume of 35 cm3, what is the density of aluminum?

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If the density of a diamond is 3.5 g/cm3, what would be the mass of a diamond whose volume is 0.5 cm3?

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A comparison of the density of a substance and the density of water is specific gravity

SINK or FLOATIn Water (D = 1.0 g/mL)

Float

Float

Float

Sink

Sink

Sink

Float

Float

(alcohol)

(fuel)