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Cornell Notes 4.1 Density December 21, 2011 Pages 115 and 117 Density • Density describes how much mass is in a given volume of a material. Mass and Volume • Remember that mass is defined as how much matter something has. • Volume is the amount of space an object takes up. Shotput: Big Mass, Small Volume Beach Ball: Small Mass, Big Volume What is Density? • Density really means how crowded the atoms are in a given substance Dense Not So Dense Density • Solids, liquids and gases are matter, so they all have density. Density • The units used for density depends on whether the substance is solid or liquid. – For liquids use units of grams per milliliter (g/mL) – For solids use density in units of g/cm3 or kg/m3. Density of common materials • Density is a property of material independent of quantity or shape. Density of common materials • Liquids tend to be less dense than solids of the same material. • Water is an exception to this rule. • The density of solid water, or ice, is less than the density of liquid water. Finding Density • To find the density of a material, you need to know the mass and volume of a solid sample of the material. 1. Mass is measured with a balance or scale. 2. Use the displacement method or calculate the volume. Finding Density • When calculating volume, all of the units of length involved in the calculation must be the same. The Formula for Density • The formula for density is… • Density = Mass ÷ Volume •D=m/v Life and Density • Note that if volume is constant, then more mass means more density • On the other hand, if mass is constant, then more volume means less density! Why density varies Density changes for different substances because: 1. Atoms have different masses. 2. Atoms may be “packed” tightly or loosely.