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Density is an intensive property. It depends on the amount matter in an object not just the size of an object. A ton of lead will have a smaller volume than a ton of Styrofoam. The density of lead is much greater than the density of Styrofoam because there is more ‘stuff’ or matter in every cubic centimeter of lead than there is in Styrofoam. Intensive properties are characteristic of a material. They are identifiers. Other intensive properties are boiling point, melting point, hardness, color, reactivity, refractive index, reflectivity, specific heat, electrical conductivity, etc. The density for a substance is the same for large and small amounts. This is why density can be helpful to identify materials. When we pick up a two metal blocks with the same volume we can tell which one is lead and which one is aluminum because lead has a higher density (11.36 g/ml) than aluminum (2.70 g/ml). Lead is almost four times denser than aluminum. That is why we use aluminum to build airplanes and lead as a barrier to protect us from x-rays in the dentist’s office. It may be surprising that gold has a density of 19.32 g/ml. Gold is one of the most dense metals. It is one of the ‘heavy metals’ in the periodic table. Density is defined as mass divided by volume. For all substances when the volume of stuff goes up so does the mass. The mass increases when the volume increases. density = mass / volume When we include the units used in most laboratory situations density has the units of grams per milliliter or grams per cubic centimeter. density = mass in grams / volume in milliliters Density is a derived unit because it is constructed using the basic units for mass and length. You might wonder how length is involved. The length unit is part of this because the volume of the cube is figured from the length of cube edge. Volume = length x length x length = length3
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