Density

• Density

  • Density is defined as:The mass per unit volume of a material
  • Objects made from low density materials typically have a low mass
  • Similarly sized objects made from high density materials have a high mass
  • For example, a bag full of feathers is far lighter compared to a similar bag full of metal
  • Or another example, a balloon is less dense than a small bar of lead despite occupying a larger volume
• Calculating Density

  • Density is related to mass and volume by the following equation:

  p=m/v

  • Where: 
  • ρ = density (kg/m3)
  • m = mass (kg)
  • V = volume (m3)
• • Gases, for examples, are less dense than solids because the molecules are more spread out (same mass, over a larger volume)
• • Gases, for examples, are less dense than solids because the molecules are more spread out (same mass, over a larger volume)
• DENSITY

  A) Less

  B) More

  
• Density, mass, volume formula triangle

  • The units of density depend on what units are used for mass and volume:
  • If the mass is measured in g and volume in cm3, then the density will be in g/cm3
  • If the mass is measured in kg and volume in m3, then the density will be in kg/m3
  • This table gives some examples of densities on common materials
  • If a material is more dense than water (1000 kg/m3), then it will sink
• DENSITY OF MATERIALS:

  A) Air

  B) Water

  
• • The volume of an object may not always be given directly, but can be calculated with the appropriate equation depending on the object’s shape