Density = mass/ volume

• usually grams per cubic centimeter

Pure water has a density of 1.0 g/cm^3
Seawater has a density of about 1.025 g/cm^3
Gold " ~ 19.3 g/cm^3
Cement " ~ 2.7 - 3.0 g/cm^3
Chalk " ~ 1.9 - 2.8 g/cm^3
Ice " ~ .917 g/cm^3
Limestone 2.68 - 2.76 g/cm^3
Granite 2.64 - 2.76 g/cm^3 (Continents)
Basalt 2.4 - 3.1 g/cm^3 (Sea floor)


The earth is arranged by density of materials

• Metal is at the core, with stone above it composing the continents and ocean floors. Water then sits above that, with air above for the atmosphere
• Most dense on the inside to least dense on the outside

If a substance is less dense than water, it will float

• This is correllated to Archimedes' Principle (Eureka!!)
• Archimedes' Principle (the law of buoyancy) states that the buoyant force on a submerged object is equal to the weight of the fluid that is displaced by the object
• e.g. An object immmersed/floating in water is buoyed up by the weight of an object displaced.
• In simple terms, if you put a 1 kg duckie decoy made of wood (density .6 g/cm^3) into a body of water (density 1.0 g/cm^3) , it will displace 1 kg of water. If that body of water is a bathtub filled to capacity, 1 kg of water will overflow onto your bathroom floor.




• D=m/v ( .6 g = 1000 g/ volume) --> V = (1000 g / .6 g) = 1,667 cm^3

In general, if a substance is less dense than any liquid it will float. Grease, gasoline, pig fat, you name it; the Principle applies.


In the world's surface water, density dynamics are important to understanding the circulation of estuaries and the world's oceans.
In certian places, like Lake Eerie, the O2 in the water in the spring is metabolized by the organisms in the lake, and the oxygen content goes to zero. The water becomes anoxic - an = not or no; oxic = of oxygen. No oxygen.

• Sometimes this occurs in the winter locally. This phenomenon is known as "winter kill"