1. Density Density is a physical property of matter. Density is a measure of how tightly packed the particles of matter are in their natural arrangement and the size and mass of the atoms involved. Example: Styrofoam has a low density. Iron has a high density.

2. Why study density? Density is a property used to identify matter Density determines: Wind Floating of any kind Ocean currents Formation of the earth’s crust and plate tectonics Atmospheric pressure

3. How is density measured? Density is determined by the formula: Mass Density = Volume Mass is measured in grams (g). Volume is measured in milliliters (mL) or cubic centimeters (cm 3 ) or (cc) Density is expressed as grams per cubic centimeter (g/cm 3)

4. Example What is the density of a block of wood that measures 2cm x 4cm x 5cm and that has a mass of 20g? V = 2cm x 4cm x 5cm = 40 cm 3 D = M V = 20g 40 cm 3 = 0.5 g/cm 3 The answer means that “One cubic centimeter of this wood has a mass of 0.5 gram.”

5. Irregular shapes If you want to determine the volume of an object with no regular shape, you must use the technique of water displacement. An object placed in water will push away (displace) an amount of water equal to its volume. Remember: 1 milliliter = 1 cubic centimeter (cm 3 ) Put this value into the formula and solve.

6. Floating All objects on earth follow the rule: Less dense floats on more dense. Any substance less dense than water will float in water. Any vessel filled with a vapor (such as air) will float in water. (Even aircraft carriers).